68hc11 microcontroller activity board with interactive c documentation

AX-11 : 68HC11 Microcontroller Activity board doumentation��1

AX-1168HC11 microcontroller

Activity boardwith Interactive C

Documentation

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(C) Innovative Experiment Co.,Ltd.

2��AX-11 : 68HC11 Microcontroller Activity board doumentation

The AX-11 68HC11 Microcontroller Activity board is developed based-on Handyboard

and Extension board; the open source controller board from MIT, USA. The current version

is Revision 6 (R6). Innovative Experiment Co.,Ltd (Thailand) modify and change some

libraries to support many alternate functions. All information of hardware modification is

opened to public.

The Handy Board is distributed under MIT’s free licensing policy, in which the design may

be licensed for for personal, educational, or commercial use with no charge.

Interactive C (IC) is provided free of charge as a service to educators and the general

public. IC7.08ax supports the Handy Board with Expansion Board and AX-11 board. IC is

property of KISS Institute for Practical Robotics, a 501(c)3 nonprofit organization.

Interactive C was written by Randy Sargent of the KISS Institute for Practical Robotics.

Randy was assisted by Mark Sherman. Portions of the code and the libraries are based on

the public distribution of Interactive C 2.8 written by Randy Sargent, Anne Wright and

Fred Martin.


Contents

Chapter 1 : Hardware Introduction.........................................................51.1 AX-11 Activity board features

1.2 Interactive C software

1.3 Preparation the Interactive C with AX-11 Activity board

1.4 Firmware downloading

1.5 Testing the Interactive C program

1.6 Things to be know when downloading the program to the AX-11

1.7 The AX-11 Power supply

1.8 How to use AX-11 Activity board with USB to RS-232 serial port converter

1.9 Basic Problem Solving

Chapter 2 : Interactive C Programming Reference.................................31

Chapter 3 : Interactive C Library..............................................................613.1 Commonly Used IC library Functions

3.2 Processes

3.3 Encoders

3.4 Basic Experiment

3.4.1 Controlling the DC motor

3.4.2 Controlling RC-Servo motors

3.4.3 Controlling the SWITCH sensor

3.4.4 Light Detection

3.4.5 GP2D120 Reading


The AX-11 is a modified version of the popular Handy board from MIT and the first

ever microcontroller board used for learning C language by Interactive C programming.

The AX-11 is a 6811-based microcontroller system that lets you build mobile robots for

educational, hobbyist, and industrial purposes. People use the AX-11 Board to run robot

design courses and competitions at the university and high school level, build robots for fun,

and control industrial devices.

1.1 AX-11 Activity board featuresThis board uses the 68HC11 microcontroller and has 32KB non-volatile RAMs, 9-

digital inputs , 21-analog inputs, 4-DC motor driver, 6-Servo motor driver, 16x2 LCD module

for displaying and RS-232 serial port interface circuit with computer fro downloading the

program.

The AX-11 activity board features :

� 68HC11 microcontroller

� 32KB RAMs with backup system

� 9-digital inputs

� 8-bit Analog to Digial Converter 21-channel

� Input Capture and Output compare port for interfacing special sensors

such as Ultrasonic ranger, Encoder, Digital Compass

� 4-DC motor driver with indicators

� 6-Servo motor driver

� a 16x2 LCD module with LED back light for displaying

� 2 of Button switch for START and STOP operation

� One KNOB for Analog to Digial Converter demonstration

� Piezo speaker

� RS-232 serial port interface for downloadin and interaction the software

� 6 pieces of AA battery holder. Support all alcaline and rechargable type

� Buit-in recharging circuit

� +7.2 or +9Vdc supply from battery (not included) or +12Vdc supply from

DC adaptor

Chapter 1Hardware introduction


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The AX-11 activity board are designed to support the learning of microcontroller

with high language programming in C by Intreractive C. Besides you can use the AX-11

activity board to study about 68HC11 microcontroller architecture with Assembly langauge

programming or Basic or ANSI C.

With expansion ports, you can interface 68HC11 microcontroller with simple and

advance external devices such as Real-Time Clock IC, Ultrasonic ranger, 2-wires devices,

Digital compass and more.

AX-11 activity board interfaces with computer serial port for downloading the In-

teractive C firmware and code. User code will be stored in memory with back up circuit.

The code is saved although the power off about 250 hours continually. The LOW BATT red

indicator will shows if the battery low power. It need to change the battery if you use

alcaline type and charge with the external DC adaptor. AX-11 board has built-in low

current battery charger circuit. If use 1800mAH, need 16 hours charging time. User who

need to speed the battery charging, the external battery charger is required. We suggest

use the 1 or 2 cells battery fast chargere; V-6280 Vanson (show in the Figure 1-4).


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1.2 Interactive C software1.2.1 System requirements

� CPU Celeron 300MHz or higher

� 10MB Harddisk space

� 32MB RAM or higher

� CD-ROM drive

� Free serial port RS-232 or USB to Serial port converter if computer available only

USB port (UCON-232S is recommended).

� Microsoft Windows 98SE or higher, Window XP service pack 2 is recommended.


1.2.2 Installation(1) Insert AX-11 CD-ROM to CD-ROM drive.

(2) Enter to Software folder and double-click on the IC708axSetup.exe. The setup

window will appear. Click on the Next button to begin the installation and click the OK or

Next button in every step until the installation complete.


1.3 Preparation the Interactive C with AX-11 activityboard

The preparations that we are about to talk about is writing the main control pro-

gram, or what they call the Firmware, into the memory of the AX-11 board. This will be

done only once in the beginning, or if the main program data disappears, or if the AX-11

board is unable to receive data from the operational program written by the program-

mer.

1.3.1 First time using AX-11 or changing the new battery(1) Upside down the AX-11 board. Open the battery holder cover. Put 6 pieces of

AA battery. Becareful the battery polarity.

(2) Turn-on the POWER switch. If the batttery power level more enough, the green

PWR. LED will light.

(3) In first time using, at LCD screen of the AX-11 activity board will display :

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If no anything to show, may be from 2 reasons as follows.

(3.1) Firmware lost. Need to download again.

(3.2) There is any code into AX-11 memory. User can download the new

code to run continue.

Normally, AX-11 board has the memory back-up system. It can save the data or

code about 250 hours (10 days approximation). Therefore the changing new battery af-

ter empty will not affect to the memory.


1.3.2 Use the external DC power supply(1) AX-11 kit provides the adjustable DC adaptor for supplying the AX-11 activity

board. Before using, select the output voltage to +12V. Plug the DC adaptor to a wall

outlet.

(2) Make sure the battery holder of the AX-11 board empty. Do not connect the

DC adaptor to AX-11 board if the alcaline batteries are in the holder except using the

rechargable batteries.

(3) Connect the DC adaptor to the DC in jack of AX-11 board, making sure the

power switch is off.

(4) Turn-on the POWER switch. The green PWR. LED will light following the Figure 1-5.

WARNING ! : If using the external DC adaptor, MUST REMOVE or DO NOT PUT ANY ALCALINEBATTERIES INTO THE BATTERY HOLDER to protect the alcaline batteries burning.

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1.3.3 How to use with the rechargable battery(1) The new rechargable battery need to charge befroe using. The AX-11 activity

has buit-in low current charger circuit. User can put the new rechargable battery into the

holder at the back of the AX-11 board and charge with +12V DC adaptor. The charging

time 16 hours for 1800mAH rating.

(2) Select the output voltage to +12V. Plug the DC adaptor to a wall outet.

(3) Connect the DC adaptor to the DC in jack of AX-11 board, making sure the

power switch is off. No need to turn-on POWER. The yellow CHG. LED will light to indicate

the charging operation. This indicator will dim when the battery voltage full.

(4) To faster charging, the 6 cells AA or more external battery charger is required.


1.3.4 Interface to computer

1.3.4.1 Interface with the RS-232 serial port or COM port

If your computer has a free RS-232 serial port or COM port, you can connect the

AX-11 baord with the COM port directly by CX-4 serial port cable (included with AX-11 kit).

The green SER. LED will light to confirm the connection following the figure below.

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1.3.4.2 Interface with USB port

Many modern computer and laptop not available the COM port. Thus, the

conenction of AX-11 with these machine must do with USB port. The USB to RS-232 serial

port comverter is required. The UCON-232S is recommended (see more info at

www.inexlobal.com or your INEX’s distributor nearby you) . The connection diagram is

shown the figure below.

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Before using the USB to RS-232 serial port converter do not forget install its driver

and checking the USB Serial port address by clicking to the Control panel � System �

Hardware � Device manager �� ports.


1.4 Firmware downloading(1) Turn on the POWER switch on the AX-11 board. If the voltage of the battery on

the AX-11 is enough, the green PWR LED will be lit brightly. If not, the LED will be dimly

displayed and the red BATT LED will indicate that the voltage level is low. Must change the

battery first or use the +12V DC Adaptor that came with the AX-11 board as the power

supply instead by connecting it to the outlet on the board. Make sure the batteryinside AX-11 is rechargable type. If not, must remove all batteries first.Once power is supplied, the yellow CHG. LED will light, and the red LED will disappear.

(2) Take the AX-11 and connect it to the serial port of the computer . The green SER

LED will light, indicating that the connection of the AX-11 to the serial port of the com-

puter was successful, and is ready for use.

(3) Open the Interactive C by entering to Start � Program � Interactive C 7.08ax

� Interactive C7.08ax. The title icon will appear for a moment.

The Choose target window will apppear following. Select the AX-11R6. Click

on the OK button.


(4) IC Port Selection window will appear. Click at the COM port address that con-

nect with AX-11 board and click on the OK button to next.

(5) If your AX-11 board does not install firmware or lost, the SerialConnectDialog will

appear. Click on the Download Firmware button.


(6) Firmware Download will appear and shows the steps in downloading the firm-

ware to the AX-11 board

(6.1) Start by connecting the download cable to the serial port and to the

AX-11 board. The green SER. LED is lit.

(6.2) Turn off the POWER switch.


(6.3) Press the STOP switch on the AX-11 board. While still holding it down,

turn on the power of the AX-11 board. Both LED at PWR. and BATT. must off. Now the AX-

11 board ready for firmware downloading.

If the PWR LED is lit, it means the board is unable to enter the down-

load mode of the program, and to check the download cable again before repeating

the steps for download.

If the BATT LED is lit, it means the voltage supply of the battery is low

and needs to be recharged for at least another 30 minutes before using it again if use

rechargable battery or chage the new batteries if use alcaline type.

(7) If everything is alright, click on the Download Firmware button.


(8) Download main library following.

(9) After downloading, the AX-11 board will beep a sound and the display will

show following message below.

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(10) The Interactive C program will then go to the Interaction window, which is

used for testing the program.

The AX-11 activity board is now ready for program coding and operation.


1.5 Testing the Interactive C ProgramAfter downloading the main control program, or the firmware, the next step is to

write a basic function to test the operation of the AX-11.

(1) Go to the Interaction window, type in the function

Printf (“Hello world !\n”);

Then press Enter.

(2) The monitor shows the results from the AX-11, displaying �� on

the top sentence. The display of the Interaction window will display the message. This

means that the AX-11 board can now interact with the Interactive C program.

(3) Next we will create a simple Interactive C program to use with the AX-11 board.

(3.1) Click New to create a new program folder.

(3.2) Type in the program below, and save it as hello.ic.

void (main) void;

{

printf(“Hello world !\n”);

beep();

}


(3.3) Click Download to download the program. A window will appear ask-ing to save the file *.ic first. Here, the file is hello.ic. A window displaying the status of thedownload will then appear.

(3.4) Run the program by

Method 1: Turn off and on the POWER switch once to reset the AX-11board.

Method 2: Run the program by clicking Run Main on the Interactive Cwindow.

The message �� will appear on the top of the AX-11

display screen.


1.6 Things to be know when downloading theprogram to the AX-11

If the AX-11 and Interactive C program is used together continuously without turn-

ing off the program, the programmer would be able to download and test the program

anytime, even when the POWER switch is turned off. This is because the program is stored

in a non-volatile system memory.

If the Interactive C program is closed and reopened again while the AX-11 board

is still on, and the firmware still operating, the communication between the AX-11 and the

Interactive C program must be reestablished. Choose the serial port used to communi-

cate, and then click Connect Now. A window displaying the status of downloading the

Interactive C library to the AX-11 board will appear as seen in the picture.

Then we will go to the Interaction window, causing the program that was saved in

the memory previously to have disappeared; therefore it must be downloaded again.

This means that every time the Interactive C program is closed and opened again,

the user must always download the program he needs into the memory again. This is

because the Interactive C program is a program that needs to be connected to the

hardware in order to check its status continuously. Therefore, if the communication is lost

because it was turned off, the communication must always be reestablished at the be-

ginning by downloading the program’s library to the AX-11 board.


1.7 The AX-11 Power SupplyThe AX-11 uses 6 serial batteries size AA with a voltage of 1.2V (Ni-MH or Ni-CD) or

1.5V (alcaline) 1800mAH or higher, therefore resulting in a supply of at least 7.2V or 9V

1800 mAH or higher. The recommended time in charging the batteries is at least 10 to 15

hours if use AX-11 built-in low current charger circuit.

If the AX-11 board is fully charged, it can be used continuously for 2-4 hours, de-

pending on the number of peripherals connected and the amount of voltage they use.

1.8 How to use AX-11 activity board with USB toRS-232 serial port converter

Normally the AX-11 activity board will connect with computer’s COM port by using

the CX-4 serial cable. The figure 1-7 shows the connection diagramn of the CX-4 cable.

However many modern computers or laptops avialable only USB port. Using with AX-11

they are need the USB to RS-232 Serial port converter.

1.8.1 UCON-232SThis is a compact size RS232 Serial to USB Convertor. Its fully compatible with all our

robotic kits and microcontroller for Laptop or Desktop users whose computers do not have

a RS232 Serial Port.

The mainly function of this converter is making the Virtual COM port compatible

with true RS-232 serial port. The figure 1-8 shows the UCON-232S photo and features.

The UCON-232S is used FT232RL from FTDI. It is USB-UART converter chip. FTDI support

the driver for computer to know this device. You can see more information and down-

load the latest driver at www.ftdichip.co.uk or www.parallax.com.

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(3) Plug the UCON-232S to USB port. Wait a moment. The blue LED of UCON-232S

lights ready to use.

(4) Check the COM port address by clicking Start � Control Panel � System �

Hardware � Device Manager

• FT232RL USB to Serial TTL-level UART converter chip

• UART interface support for 7 or 8 data bits, 1 or 2 stop

bits and all parity.

• Fully assisted hardware or X-On / X-Off software hand-

shaking.

• Data transfer rates 300 baud to 1 Megabaud (RS232).

• Full UART pin configuration includes TxD, RxD, DTR, DSR,

RTS, CTS, DCD and RI

• Get power from USB bus and supply power to exter-

nal not over 100mA.

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(5) See the list of USB serial port and remember the COM port address to work with

AX-11 board. Normally UCON-232S will create COM3 or above.


1.8.3 How to work with AX-11 activity board and Interactive C(1) Connect the DB-9 end of the CX-4 serial cable to UCON-232S and the other end

connect to AX-11 board. Turn-on power.

(2) Open Interactive C. Choose the hardware to AX-11R6 and click on the OKbutton. The IC Port Selection window will appear.

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(4) The Serial Port Input dialog will appear. Put the message \\.\comX to choose

the COM port that created from UCON-232S. Thus, X is number of COM port. From ex-

ample below is COM15. Click on the OK button.


(5) The IC Port Selection window will appear again and show only one COM port

selection. Click at the circle to choosing and click on the OK button.

(6) Interaction window of Interactive C will appear. Observe the title bar. It shows

the COM port that interface with Interactive C. For this example is COM15.


1.9 Basic Problem Solving1.9.1 If the downloaded program does not work.

Solve by

- Check the download cable by checking if the SER LED is green.

- Check the power supply by checking if the BATT LED is red. If it is lighted

bright it means that the battery is low. Change the new battery if using alcaline type or

Use the external power from the DC adapter +12V 500 mA (making sure no any alcaline

battery in the holder before plug the DC power to AX-11 board)

- Check the correct COM port especially using USB to Serial port converter.

- Download the firmware again.

1.9.2 If the AX-11 cannot communicate with the Interactive CSolve by

- Check the power supplied to the AX-11 by checking if the PWR LED is green.



bright it means that the battery is low. Change the new battery if using alcaline type or

Use the external power from the DC adapter +12V 500 mA (making sure no any alcaline

battery in the holder before plug the DC power to AX-11 board)


- If everything is ok, download the firmware again.

1.9.3 If the firmware can not be downloadedSolve by

- Check the power supplied to the AX-11 by checking if the PWR LED is green.



bright it means that the battery is low. Use the external power from the DC adapter +12V

500 mA (making sure no any alcaline battery in the holder before plug the DC power to

AX-11 board)


- If it is still not working, send the robot back to the manufacturer or distribu-

tor to check its functionality

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2.1 IntroductionInteractive C (IC for short) is a C language consisting of a compiler (with interactive

command-line compilation and debugging) and a run-time machine language module.

IC implements a subset of C including control structures (for, while, if, else), local and

global variables, arrays, pointers, structures, 16-bit and 32-bit integers, and 32-bit floating

point numbers.

IC works by compiling into pseudo-code for a custom stack machine, rather than

compiling directly into native code for a particular processor. This pseudo-code (or p-

code) is then interpreted by the run-time machine language program. This unusual ap-

proach to compiler design allows IC to offer the following design tradeoffs:

� Interpreted execution that allows run-time error checking. For example, IC

does array bounds checking at run-time to protect against some programming errors.

� Ease of design. Writing a compiler for a stack machine is significantly easier

than writing one for a typical processor. Since IC’s p-code is machine-independent, port-

ing IC to another processor entails rewriting the p-code interpreter, rather than changing

the compiler.

� Small object code. Stack machine code tends to be smaller than a native

code representation.

� Multi-tasking. Because the pseudo-code is fully stack-based, a process’s

state is defined solely by its stack and its program counter. It is thus easy to task-switch

simply by loading a new stack pointer and program counter. This task-switching is handled

by the run-time module, not by the compiler.

Since IC’s ultimate performance is limited by the fact that its output p-code is inter-

preted, these advantages are taken at the expense of raw execution speed.

Chapter 2Interactive C

Programming Reference


2.2 Using ICWhen IC is running and has a connection to a compatible processor board such

as the Handy Board or RCX, C expressions, function calls, and IC commands may be

typed in the command entry portion of the interaction window.

For example, to evaluate the arithmetic expression 1 + 2, type in the following:

1 + 2;

When this expression is entered from the interaction window, it is compiled by the

console computer and then downloaded to the attached system for evaluation. The

connected board then evaluates the compiled form and returns the result, which is printed

on the display section of console interaction window.

To evaluate a series of expressions, create a C block by beginning with an open

curly brace { and ending with a close curly brace }. The following example creates a local

variable i and prints 10 (the sum of i + 7) to the board’s LCD screen:

{int i=3; printf(“%d”, i+7);}

2.3 IC InterfaceBoth new (unsaved) and saved files can be opened for editing in IC. A row of tabs

lists the files that have been opened. Clicking a file’s tab activates it for editing. The first

tab for the interface is always the interaction window.

The File menu has standard entries for New, Open, Close, Save, Save As, Print and

Exit. Under File - Save As, if no file name extension is supplied, IC automatically saves with

the “.ic” extension.

To download the active file, simply click the button. The active file will

also be saved, unless it is new, in which case the user is prompted for a “save as” file

name. Remark: a preprocessor command #use has been added to IC to specify any

other saved files (personal libraries) that need to be downloaded along with the active

file [Note: #use is quite different from the #include prepreocessor command of standard

C environments. #include is not implemented for reasons given later in the section de-

scribing the IC-preprocessor.]

If a downloaded program does not do what is intended, it may corrupt the p-code

interpreter, particularly if pointers are being employed. The interface provides an option

under the Settings button for downloading the firmware to reinitialize the board.

When there is a connection to a board and the downloaded programs include

“main”, then “main” can be executed using the button. The button will

halt execution of the attached system.


FileNew (Ctrl+N) Create the new file

Open (Ctrl-O) Open the exist file

Close (Ctrl+W) Close the active file

Save (Ctrl + S) Save the active file

Save As Save the active file to

new name

Print (Ctrl+P) Print out the active code

Exit Exit program

EditUndo Undo the last edit action

Redo Redo the last edit action

Cut Cut text to clipboard

Copy Copy text to clipboard

Paste Paste text from clipboard

Select all Select all text

Find Find words

Find Next Find next words

Goto line Go to the target line

Indent Indent message

Indent All Indent all file

Tools :Check parens Check parentheses

Upload array Upload data from array

List functions Show the list of function

List global variables Show the list of global variable

List loaded files Show the downloaded file

List # Define Show the list of defined

variable

View diagram Show AX-11 board layout

Download firmware Download firmware to AX-11

Download Libraries Download library of IC7.08ax

SettingIncerase Font size

Decrease Font size

Change controller type

Change serial port

Disconnect serial port

HelpManual Interactive C HTML manual

About License of IC

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Interactive C function1. Printing

printf Display message on the LCD screen of AX-11 board

2. Digitla Input Outputclear_digital_out Clear or send logic “0” to the specific port

set_digital_out Set or send logic “1” to the specific port

test_digital_out Test logic at the specific digital output port

3. Motoralloff or a0 Off all motor driver

bk Backward driving

fd Forward driving

init_expbd_servos Enable servo motor driver

motor Choose motor driver power; value is -100 to 100

off Off the specific motor driver channel

4. Soundbeep Generate 500Hz signal in 0.3 second approximation

beeper_off Turn off sound

beeper_on Turn on sound with the latest frequency

set_beeper_pitch Set the sound frequency

Tone Generate the sound with the specific frequency of

set_beeper_pitch function and set the duration time in second.

5. Timingmseconds Count time in millisecond unit

msleep Set delay time in millisecond unit

reset_system_time Reset time

seconds Count time in second unit

sleep Set delay time in second unit


6. Sensoranalog Get value from the specific analog input

digital Get value from the specific digital input

disable_encoder Disable the encoder function

enable_encoder Enable the encoder function

knob Read value from potentiometer at KNOB position of AX-11

read_encoder Read data from the encoder function

reset_encoder Reset the encoder function

start_button Read START button value

start_press Loop for checking the STARTswitch is pressed

stop_button Read STOP button value

stop_press Loop for checking the STOP switch is pressed

7. Mathatan Calculate Arctangent (TAN-1). Result is in Radian unit

cos Calculate Cosine (COS). Result is in Radian unit

exp Calculate the power of natural exponential (en)

exp10 Calculate the power of 10 (10n)

log Calculate the natural logarithm

log10 Calculate the logarithm of 10

random Random number in range 2 to 32,767

sin Calculate Sine (SIN). Result is in Radian unit

sqrt Calculate the square-root of integer

tan Calculate Tangent (TAN). Result is in Radian unit

8. Multi-taskinghog_processor Allocates an additional 256 milliseconds of execution to the

currently running process.

defer Makes a process swap out immediately after the function is

called.

kill_process Destroy processes

start_process Start a process, which then runs in parallel with other active

processes.


Under the Tools menu, among other options, are ones for listing downloaded files,

global variables, and functions (including library functions).

The interface provides additional capabilities for program entry/edit, minor adjust-

ment to the display, and for setting up the serial interface to a board.

C programs are automatically formatted and indented. Keywords, library func-

tions, comments, and text strings are high-lighted with color unless this feature is turned

off.

IC does parenthesis-balance-highlighting when the cursor is placed to the right of

any right parenthesis, bracket, or brace.

2.4 The main() FunctionAfter functions have been downloaded to a board, they can be invoked from IC

so long as the board is connected. If one of the functions is named main(), it can be run

directly from the interface as noted earlier, and otherwise will be run automatically when

the board is reset.

Note: to reset the Handy Board without running the main() function (for instance,

when hooking the board back to the computer), hold down the board’s Start button

while activating the board. The board will then reset without running main().

2.5 IC versus Standard CThe IC programming language is based loosely on ANSI C. However, there are

major differences.

Many of these differences arise from the desire to have IC be “safer” than stan-

dard C. For instance, in IC, array bounds are checked at run time; for this reason, arrays

cannot be converted to pointers in IC. Also, in IC, pointer arithmetic is not allowed.

Other differences are due to the desire that the IC runtime be small and efficient.

For instance, the IC printf function does not understand many of the more exotic format-

ting options specified by ANSI C.

Yet other differences are due to the desire that IC be simpler than standard C. This

is the reason for the global scope of all declarations.

In the rest of this document, when we refer to “C”, the statement applies to both IC

and standard C. When we wish to specify one or the other, we will refer to either “IC” or

“standard C”. When no such qualifiers are present, you should assume that we are talking

about IC.


2.5.1 A Quick C TutorialMost C programs consist of function definitions and data structures. Here is a simple

C program that defines a single function, called main.

/* Simple example IC Programmer’s Manual */

void main()

{

printf(“Hello, world!\n”); // Something simple

}

The expression

/* <text> */

forms a multi-line or bracketed comment. In contrast, text that starts with “//” forms

a single line comment, which continues only to the end of the line. Comments are ig-

nored by IC when the program is compiled.

All functions must have a return type. Since main does not return a value, it uses

void, the null type, as its return type. Other types include integers (int) and floating point

numbers (float). This function declaration information must precede each function defini-

tion.

Immediately following the function declaration is the function’s name (in this case,

main). Next, in parentheses, are any arguments (or inputs) to the function. main has none,

but an empty set of parentheses is still required.

After the function arguments is an open curly-brace {. This signifies the start of the

actual function code. Curly-braces signify program blocks, or chunks of code.

Next comes a series of C statements. Statements demand that some action be

taken. Our demonstration program has a single statement, a printf (formatted print). This

will print the message “Hello, world!” to the LCD display. The \n indicates end-of-line. The

printf statement ends with a semicolon (;). All C statements must be ended by a semico-

lon. Beginning C programmers commonly make the error of omitting the semicolon that is

required to end each statement.

The main function is ended by the close curly-brace }.

Let’s look at an another example to learn some more features of C. The following

code defines the function square, which returns the mathematical square of a number.

int square(int n)

{

return(n * n);

}


The function is declared as type int, which means that it will return an integer value.

Next comes the function named square, followed by its argument list in parenthe-

ses. square has one argument, n, which is an integer. Notice how declaring the type of

the argument is done similarly to declaring the type of the function.

When a function has arguments declared, those argument variables are valid within

the “scope” of the function (i.e., they only have meaning within the function’s own code).

Other functions may use the same variable names independently.

The code for square is contained within the set of curly braces. In fact, it consists of

a single statement: the return statement. The return statement exits the function and re-

turns the value of the C expression that follows it (in this case “n * n”).

Except where grouped by parentheses, expressions are evaluated according to a

set of precedence rules associated with the various operations within the expression. In

this case, there is only one operation (multiplication), signified by the “*”, so precedence

is not an issue.

Let’s look at an example of a function that performs a function call to the square

program.

float hypotenuse(int a, int b)

{

float h;

h = sqrt((float)(square(a) + square(b)));

return(h);

}

This code demonstrates several more features of C. First, notice that the floating

point variable h is defined at the beginning of the hypotenuse function. In general, when-

ever a new program block (indicated by a set of curly braces) is begun, new local vari-

ables may be defined.

The value of h is set to the result of a call to the sqrt function. It turns out that sqrt is

a built-in IC function that takes a floating point number as its argument.

We want to use the square function we defined earlier, which returns its result as an

integer. But the sqrt function requires a floating point argument. We get around this type

incompatibility by coercing the integer sum (square(a) + square(b)) into a float by pre-

ceding it with the desired type, in parentheses. Thus, the integer sum is made into a float-

ing point number and passed along to sqrt.

The hypotenuse function finishes by returning the value of h.


2.6 Data ObjectsVariables and constants are the basic data objects in a C program. Declarations

list the variables to be used, state what type they are, and may set their initial value.

2.6.1 VariablesVariable names are case-sensitive. The underscore character is allowed and is of-

ten used to enhance the readability of long variable names. C keywords like if, while, etc.

may not be used as variable names.

Functions and global variables may not have the same name. In addition, if a

local variable is named the same as a function or a global variable, the local use takes

precedence; ie., use of the function or global variable is prevented within the scope of

the local variable.

2.6.1.1 Declaration

In C, variables can be declared at the top level (outside of any curly braces) or at

the start of each block (a functional unit of code surrounded by curly braces). In general,

a variable declaration is of the form:

<type> <variable-name>; or

<type> <variable-name>=<initialization-data>;

In IC, <type> can be int, long, float, char, or struct <struct-name>, and determines

the primary type of the variable declared. This form changes somewhat when dealing

with pointer and array declarations, which are explained in a later section, but in general

this is the way you declare variables.

2.6.1.2 Local and Global Scopes

If a variable is declared within a function, or as an argument to a function, its bind-

ing is local, meaning that the variable has existence only within that function definition. If

a variable is declared outside of a function, it is a global variable. It is defined for all

functions, including functions which are defined in files other than the one in which the

global variable was declared.

2.6.1.3 Variable Initialization

Local and global variables can be initialized to a value when they are declared. If

no initialization value is given, the variable is initialized to zero.

All global variable declarations must be initialized to constant values. Local variables

may be initialized to the value of arbitrary expressions including any global variables, func-

tion calls, function arguments, or local variables which have already been initialized.


Here is a small example of how initialized declarations are used.

inti=50; /* declare i as global integer; initial value 50 */longj=100L; /* declare j as global long; initial value 100 */intfoo(){

intx; /* declare x as local integer; initial value 0 */longy=j; /* declare y as local integer; initial value j */

}

Local variables are initialized whenever the function containing them is executed. Glo-

bal variables are initialized whenever a reset condition occurs. Reset conditions occur when:

1. Code is downloaded;

2. The main() procedure is run;

3. System hardware reset occurs.

2.6.1.4 Persistent Global Variables

A special persistent form of global variable, has been implemented for IC. A persis-

tent global variable may be initialized just like any other global variable, but its value is

only initialized when the code is downloaded and not on any other reset conditions. If no

initialization information is included for a persistent variable, its value will be initialized to

zero on download, but left unchanged on all other reset conditions.

To make a persistent global variable, prefix the type specifier with the keyword

persistent. For example, the statementpersistent int i=500;

creates a global integer called i with the initial value 500.

Persistent variables keep their state when the board is turned off and on, when main is

run, and when system reset occurs. Persistent variables will lose their state when code is down-

loaded as a result of loading or unloading a file. However, it is possible to read the values of your

persistent variables in IC if you are still running the same IC session from which the code was

downloaded. In this manner you could read the final values of calibration persistent variables,

for example, and modify the initial values given to those persistent variables appropriately.

Persistent variables were created with two applications in mind:

� Calibration and configuration values that do not need to be re-calculated

on every reset condition.

� Robot learning algorithms that might occur over a period when the robot is

turned on and off.


2.6.2 Constants

2.6.2.1 Integer Constants

Integers constants may be defined in decimal integer format (e.g., 4053 or -1),

hexadecimal format using the “0x” prefix (e.g., 0x1fff), and a non-standard but useful

binary format using the “0b” prefix (e.g., 0b1001001). Octal constants using the zero prefix

are not supported.

2.6.2.2 Long Integer Constants

Long integer constants are created by appending the suffix “l” or “L” (upper- or

lower- case alphabetic L) to a decimal integer. For example, 0L is the long zero. Either the

upper or lower-case “L” may be used, but upper-case is the convention for readability.

2.6.2.3 Floating Point Constants

Floating point numbers may use exponential notation (e.g., “10e3” or “10E3”) or

may contain a decimal period. For example, the floating point zero can be given as “0.”,

“0.0”, or “0E1”, but not as just “0”. Since the board has no floating point hardware, floating

point operations are much slower than integer operations, and should be used sparingly.

2.6.2.4 Characters and String Constants

Quoted characters return their ASCII value (e.g., ‘x’).

Character string constants are defined with quotation marks, e.g., “This is a char-

acter string.”.

2.6.2.5 NULL

The special constant NULL has the value of zero and can be assigned to and com-

pared to pointer or array variables (which will be described in later sections). In general,

you cannot convert other constants to be of a pointer type, so there are many times

when NULL can be useful.

For example, in order to check if a pointer has been initialized you could compare

its value to NULL and not try to access its contents if it was NULL. Also, if you had a defined

a linked list type consisting of a value and a pointer to the next element, you could look

for the end of the list by comparing the next pointer to NULL.


2.6.3 Data TypesIC supports the following data types:

2.6.3.1 16-bit Integers

16-bit integers are signified by the type indicator int. They are signed integers, and

may be valued from -32,768 to +32,767 decimal.

2.6.3.2 32-bit Integers

32-bit integers are signified by the type indicator long. They are signed integers,

and may be valued from -2,147,483,648 to +2,147,483,647 decimal.

2.6.3.3 32-bit Floating Point Numbers

Floating point numbers are signified by the type indicator float. They have approxi-

mately seven decimal digits of precision and are valued from about 10^-38 to 10^38.

2.6.3.4 8-bit Characters

Characters are an 8-bit number signified by the type indicator char. A character’s

value typically represents a printable symbol using the standard ASCII character code,

but this is not necessary; characters can be used to refer to arbitrary 8-bit numbers.

2.6.3.5 Pointers

IC pointers are 16-bit numbers which represent locations in memory. Values in

memory can be manipulated by calculating, passing and dereferencing pointers repre-

senting the location where the information is stored.

2.6.3.6 Arrays

Arrays are used to store homogenous lists of data (meaning that all the elements of

an array have the same type). Every array has a length which is determined at the time

the array is declared. The data stored in the elements of an array can be set and re-

trieved in the same manner as for other variables.

2.6.3.7 Structures

Structures are used to store non-homogenous but related sets of data. Elements of a

structure are referenced by name instead of number and may be of any supported type.

Structures are useful for organizing related data into a coherent format, reducing

the number of arguments passed to functions, increasing the effective number of values

which can be returned by functions, and creating complex data representations such as

directed graphs and linked lists.


2.6.4 PointersThe address where a value is stored in memory is known as the pointer to that

value. It is often useful to deal with pointers to objects, but great care must be taken to

insure that the pointers used at any point in your code really do point to valid objects in

memory.

Attempts to refer to invalid memory locations could corrupt your memory. Most

computing environments that you are probably used to return helpful messages like ‘Seg-

mentation Violation’ or ‘Bus Error’ on attempts to access illegal memory. However, you

won’t have this safety net on the board you are connecting to. Invalid pointer

dereferencing is very likely to go undetected, and will likely render invalid your data, your

program, or even the pcode interpreter.

2.6.4.1 Pointer Safety

In past versions of IC, you could not return pointers from functions or have arrays of

pointers. In order to facilitate the use of structures, these features have been added to

the current version. With this change, the number of opportunities to misuse pointers have

increased. However, if you follow a few simple precautions you should do fine.

First, you should always check that the value of a pointer is not equal to NULL (a

special zero pointer) before you try to access it. Variables which are declared to be point-

ers are initialized to NULL, so many uninitialized values could be caught this way.

Second, you should never use a pointer to a local variable in a manner which

could cause it to be accessed after the function in which it was declared terminates.

When a function terminates the space where its values were being stored is recycled.

Therefore not only may dereferencing such pointers return incorrect values, but assigning

to those addresses could lead to serious data corruption. A good way to prevent this is to

never return the address of a local variable from the function which declares it and never

store those pointers in an object which will live longer than the function itself (a global

pointer, array, or struct). Global variables and variables local to main will not move once

declared and their pointers can be considered to be secure.

The type checking done by IC will help prevent many mishaps, but it will not catch

all errors, so be careful.

2.6.4.2 Pointer Declaration and Use

A variable which is a pointer to an object of a given type is declared in the same

manner as a regular object of that type, but with an extra * in front of the variable name.

The value stored at the location the pointer refers to is accessed by using the *

operator before the expression which calculates the pointer. This process is known as

dereferencing.


The address of a variable is calculated by using the & operator before that vari-

able, array element, or structure element reference.

There are two main differences between how you would use a variable of a given

type and a variable declared as a pointer to that type.

For the following explanation, consider X and Xptr as defined as follows:

long X; long *Xptr;

Space Allocation — Declaring an object of a given type, as X is of type

long, allocates the space needed to store that value. Because an IC long takes four bytes

of memory, four bytes are reserved for the value of X to occupy. However, a pointer like

Xptr does not have the same amount of space allocated for it that is needed for an

object of the type it points to. Therefore it can only safely refer to space which has already

been allocated for globals (in a special section of memory reserved for globals) or locals

(temporary storage on the stack).

Initial Value — It is always safe to refer to a non-pointer type, even if it hasn’t

been initialized. However pointers have to be specifically assigned to the address of le-

gally allocated space or to the value of an already initialized pointer before they are safe

to use.

So, for example, consider what would happen if the first two statements after X

and Xptr were declared were the following:

X=50L; *Xptr=50L;

The first statement is valid : it sets the value of X to 50L. The second statement would

be valid if Xptr had been properly initialized, but in this case it has not. Therefore, this

statement would corrupt memory.

Here is a sequence of commands you could try which illustrate how pointers and

the * and & operators are used. It also shows that once a pointer has been set to point at

a place in memory, references to it actually share the same memory as the object it

points to:

X=50L; /* set the memory allocated for X to 50 */Xptr=&X; /* set Xptr to point to memory address of X */printf(“%d “,*Xptr); /* dereference Xptr; value at address is 50 */X=100L; /* set X to the value 100 */printf(“%d “,*Xptr); /* dereference again; value is now 100 */*Xptr=200L; /* set value at address given by Xptr to 200 */printf(“%d\n”,X); /* check that the value of X changed to 200 */


2.6.4.3 Passing Pointers as ArgumentsPointers can be passed to functions and functions can change the values of the

variables that are pointed at. This is termed call-by-reference; a reference, or pointer, to a

variable is given to the function that is being called. This is in contrast to call-by-value, the

standard way that functions are called, in which the value of a variable is given the to

function being called.

The following example defines an average_sensor function which takes a port num-

ber and a pointer to an integer variable. The function will average the sensor and store

the result in the variable pointed at by result.

Prefixing an argument name with * declares that the argument is a pointer.

void average_sensor(int port, int *result){

int sum = 0;int i;for (I = 0; I < 10; i++) sum += analog(port);*result = sum/10;

}

Notice that the function itself is declared as a void. It does not need to return

anything, because it instead stores its answer in the memory location given by the pointer

variable that is passed to it.

The pointer variable is used in the last line of the function. In this statement, the

answer sum/10 is stored at the location pointed at by result. Notice that the * is used to

assign a value to the location pointed by result.

2.6.4.4 Returning Pointers from FunctionsPointers can also be returned from functions. Functions are defined to return point-

ers by preceeding the name of the function with a star, just like any other type of pointer

declaration.

int right,left;int *dirptr(int dir){

if (dir==0){

return(&right);}if (dir==1){

return(&left);}return(NULL);

}

The function dirptr returns a pointer to the global right when its argument dir is 0, a

pointer to left when its argument is 1, and NULL if its argument is other than 0 or 1.


2.6.5 ArraysIC supports arrays of characters, integers, long integers, floating-point numbers, struc-

tures, pointers, and array pointers (multi-dimensional arrays). While unlike regular C arrays in a

number of respects, they can be used in a similar manner. The main reasons that arrays are

useful are that they allow you to allocate space for many instances of a given type, send an

arbitrary number of values to functions, and provide the means for iterating over a set of values.

Arrays in IC are different and incompatible with arrays in other versions of C. This

incompatibility is caused by the fact that references to IC arrays are checked to insure that

the reference is truly within the bounds of that array. In order to accomplish this checking in

the general case, it is necessary that the size of the array be stored with the contents of the

array. It is important to remember that an array of a given type and a pointer to the same

type are incompatible types in IC, whereas they are largely interchangeable in regular C.

2.6.5.1 Declaring and Initializing ArraysArrays are declared using square brackets. The following statement declares an

array of ten integers:

int foo[10];

In this array, elements are numbered from 0 to 9. Elements are accessed by enclos-

ing the index number within square brackets : foo[4] denotes the fifth element of the array

foo (since counting begins at zero).

Arrays are initialized by default to contain all zero values. Arrays may also be initial-

ized at declaration by specifying the array elements, separated by commas, within curly

braces. If no size value is specified within the square brackets when the array is declared

but initialization information is given, the size of the array is determined by the number of

elements given in the declaration. For example,

int foo[]= {0, 4, 5, -8, 17, 301};

creates an array of six integers, with foo[0] equaling 0, foo[1] equaling 4, etc.

If a size is specified and initialization data is given, the length of the initialization

data may not exceed the specified length of the array or an error results. If, on the other

hand, you specify the size and provide fewer initialization elements than the total length

of the array, the remaining elements are initialized to zero.

Character arrays are typically text strings. There is a special syntax for initializing

arrays of characters. The character values of the array are enclosed in quotation marks:

char string[]= “Hello there”;

This form creates a character array called string with the ASCII values of the speci-

fied characters. In addition, the character array is terminated by a zero. Because of this

zero-termination, the character array can be treated as a string for purposes of printing

(for example). Character arrays can be initialized using the curly braces syntax, but they

will not be automatically null-terminated in that case. In general, printing of character

arrays that are not null-terminated will cause problems.


2.6.5.2 Passing Arrays as Arguments

When an array is passed to a function as an argument, the array’s pointer is actu-

ally passed, rather than the elements of the array. If the function modifies the array val-

ues, the array will be modified, since there is only one copy of the array in memory.

In normal C, there are two ways of declaring an array argument: as an array or as

a pointer to the type of the array’s elements. In IC array pointers are incompatible with

pointers to the elements of an array so such arguments can only be declared as arrays.

As an example, the following function takes an index and an array, and returns the

array element specified by the index:

int retrieve_element(int index, int array[]){

return array[index];}

Notice the use of the square brackets to declare the argument array as a pointer

to an array of integers.

When passing an array variable to a function, you are actually passing the value of

the array pointer itself and not one of its elements, so no square brackets are used.

void foo(){

int array[10];retrieve_element(3, array);

}

2.6.5.3 Multi-dimensional ArraysA two-dimensional array is just like a single dimensional array whose elements are

one- dimensional arrays. Declaration of a two-dimensional array is as follows:

int k[2][3];

The number in the first set of brackets is the number of 1-D arrays of int. The number

in the second set of brackets is the length of each of the 1-D arrays of int. In this example,

k is an array containing two 1-D arrays; k[0] is a 1-D array of color=blue>int of length 3;

k[0][1] is an color=blue>int. Arrays of with any number of dimensions can be generalized

from this example by adding more brackets in the declaration.

2.6.5.4 Determining the size of Arrays at RuntimeAn advantage of the way IC deals with arrays is that you can determine the size of

arrays at runtime. This allows you to do size checking on an array if you are uncertain of its

dimensions and possibly prevent your program from crashing.

Since _array_size is not a standard C feature, code written using this primitive will

only be able to be compiled with IC.


The _array_size primitive returns the size of the array given to it regardless of the

dimension or type of the array. Here is an example of declarations and interaction with

the _array_size primitive:

int i[4]={10,20,30};int j[3][2]={{1,2},{2,4},{15}};int k[2][2][2];_array_size(i); /* returns 4 */_array_size(j); /* returns 3 */_array_size(j[0]); /* returns 2 */_array_size(k); /* returns 2 */_array_size(k[0]); /* returns 2 */

2.6.5.5 Uploading Arrays

When an executing program is paused or has finished, IC can upload the values

stored in any global array via the serial port. This permits collecting and recording data for

purposes such as experimentation or calibration.

The IC upload array capability is accessed using the tools tab. When upload array

is activated, it lists all globally declared arrays. When an array is selected, it is opened in a

(modal) view window. The array can be copied to the clipboard, or saved to a TXT or CSV

(comma separated values) file for import to analysis software.

2.6.6 StructuresStructures are used to store non-homogenous but related sets of data. Elements of

a structure are referenced by name instead of number and may be of any supported

type.

Structures are useful for organizing related data into a coherent format, reducing




Structures are used to store non-homogenous but related sets of data. Elements of

a structure are referenced by name instead of number and may be of any supported

type. Structures are useful for organizing related data into a coherent format, reducing




The following example shows how to define a structure, declare a variable of struc-

ture type, and access its elements.


struct foo{

int i;int j;

};struct foo f1;void set_f1(int i,int j){

f1.i=i;f1.j=j;

}void get_f1(int *i,int *j){

*i=f1.i;*j=f1.j;

}

The first part is the structure definition. It consists of the keyword struct, followed by

the name of the structure (which can be any valid identifier), followed by a list of named

elements in curly braces. This definition specifies the structure of the type struct foo. Once

there is a definition of this form, you can use the type struct foo just like any other type. The

line struct foo f1; is a global variable declaration which declares the variable f1 to be

of type struct foo.

The dot operator is used to access the elements of a variable of structure type. In

this case, f1.i and f1.j refer to the two elements of f1. You can treat the quantities f1.i and

f1.j just as you would treat any variables of type int (the type of the elements was defined

in the structure declaration at the top to be int).

Pointers to structure types can also be used, just like pointers to any other type.

However, with structures, there is a special short-cut for referring to the elements of the

structure pointed to.

struct foo *fptr;void main(){

fptr=&f1;fptr->i=10;fptr->j=20;

}

In this example, fptr is declared to be a pointer to type struct foo. In main, it is set to

point to the global f1 defined above. Then the elements of the structure pointed to by fptr(in this case these are the same as the elements of f1), are set. The arrow operator is used

instead of the dot operator because fptr is a pointer to a variable of type struct foo. Note

that (*fptr).i would have worked just as well as fptr->i, but it would have been clumsier.

Note that only pointers to structures, not the structures themselves, can be passed

to or returned from functions.


2.6.7 Complex Initialization examplesComplex types — arrays and structures — may be initialized upon declaration with a

sequence of constant values contained within curly braces and separated by commas.

Arrays of character may also be initialized with a quoted string of characters.

For initialized declarations of single dimensional arrays, the length can be left blank

and a suitable length based on the initialization data will be assigned to it. Multi-dimen-

sional arrays must have the size of all dimensions specified when the array is declared. If a

length is specified, the initialization data may not overflow that length in any dimension or

an error will result. However, the initialization data may be shorter than the specified size

and the remaining entries will be initialized to 0. Following is an example of legal global

and local variable initializations:

/* declare many globals of various types */int i=50;int *ptr=NULL;float farr[3]={ 1.2, 3.6, 7.4 };int tarr[2][4]={ { 1, 2, 3, 4 }, { 2, 4, 6, 8} };char c[]=”Hi there how are you?”;char carr[5][10]={“Hi”,”there”,”how”,”are”,”you”};struct bar{

int i;int *p;long j;

} b={5, NULL, 10L};struct bar barr[2] = { { 1, NULL, 2L }, { 3 } };/* declare locals of various types */int foo(){

int x; /* local variable x with initial value 0 */int y= tarr[0][2]; /* local variable y with initial value 3 */int *iptr=&i; /* local pointer to integer

which points to the global i */int larr[2]={10,20}; /* local array larr

with elements 10 and 20 */struct bar lb={5,NULL,10L};

/* local variable of typestruct bar with i=5 and j=10 */

char lc[]=carr[2]; /* local string lc withinitial value “how” */

...}


2.7 Statements and ExpressionsOperators act upon objects of a certain type or types and specify what is to be done to

them. Expressions combine variables and constants to create new values. Statements are ex-

pressions, assignments, function calls, or control flow statements which make up C programs.

2.7.1 OperatorsEach of the data types has its own set of operators that determine which opera-

tions may be performed on them.

2.7.1.1 Integer OperationsThe following operations are supported on integers:

� Arithmetic : addition +, subtraction -, multiplication *, division /.

� Comparison : greater-than >, less-than <, equality ==, greater-than-equal

>=, less-than-equal <=.

� Bitwise Arithmetic : bitwise-OR |, bitwise-AND &, bitwise-exclusive-OR ^,

bitwise-NOT ~.

� Boolean Arithmetic : logical-OR ||, logical-AND &&, logical-NOT !.

When a C statement uses a boolean value (for example, if), it takes the integer

zero as meaning false, and any integer other than zero as meaning true. The boolean

operators return zero for false and one for true. Boolean operators && and || will stop

executing as soon as the truth of the final expression is determined. For example, in the

expression a && b, if a is false, then b does not need to be evaluated because the result

must be false. The && operator therefore will not evaluate b.

2.7.1.2 Long IntegersA subset of the operations implemented for integers are implemented for long

integers: arithmetic addition +, subtraction -, multiplication * and the integer comparison

operations. Bitwise and boolean operations and division are not supported.

2.7.1.3 Floating Point NumbersIC uses a package of public-domain floating point routines distributed by Motorola

(currently is Freescale). This package includes arithmetic, trigonometric, and logarithmic

functions. Since floating point operations are implemented in software, they are much

slower than the integer operations; we recommend against using floating point if you are

concerned about performance.

The following operations are supported on floating point numbers:

� Arithmetic : addition +, subtraction -, multiplication *, division /.

� Comparison : greater-than >, less-than <, equality ==, greater-than-equal

>=, less-than-equal <=.

� Built-in Math Functions : A set of trigonometric, logarithmic, and exponen-

tial functions is supported.


2.7.1.4 CharactersCharacters are only allowed in character arrays. When a cell of the array is refer-

enced, it is automatically coerced into a integer representation for manipulation by the

integer operations. When a value is stored into a character array, it is coerced from a

standard 16- bit integer into an 8-bit character (by truncating the upper eight bits).

2.8 Assignment Operators and ExpressionsThe basic assignment operator is =. The following statement adds 2 to the value of a.

a = a + 2;

The abbreviated form

a += 2;

could also be used to perform the same operation. All of the following binary op-

erators can be used in this fashion:

+ - * / % << >> & ^ |

2.9 Increment and Decrement OperatorsThe increment operator ++ increments the named variable. For example, the con-

struction a++ is equivalent to a= a+1 or a+= 1. A statement that uses an increment opera-

tor has a value. For example, the statement

a= 3; printf(“a=%d a+1=%d\n”, a, ++a);

will display the text “a=3 a+1=4”. If the increment operator comes after the named

variable, then the value of the statement is calculated after the increment occurs. So the

statement

a= 3; printf(“a=%d a+1=%d\n”, a, a++);

would display “a=3 a+1=3” but would finish with a set to 4. The decrement opera-

tor “—” is used in the same fashion as the increment operator.

2.10 Data Access Operators&

A single ampersand preceding a variable, an array reference, or a structure ele-

ment reference returns a pointer to the location in memory where that information is be-

ing stored. This should not be used on arbitrary expressions as they do not have a stable

place in memory where they are being stored.

*A single * preceeding an expression which evaluates to a pointer returns the value

which is stored at that address. This process of accessing the value stored within a pointer

is known as dereferencing.


[<expr>]An expression in square braces following an expression which evaluates to an ar-

ray (an array variable, the result of a function which returns an array pointer, etc.) checks

that the value of the expression falls within the bounds of the array and references that

element.

.A dot between a structure variable and the name of one of its fields returns the

value stored in that field.

->An arrow between a pointer to a structure and the name of one of its fields in that

structure acts the same as a dot does, except it acts on the structure pointed at by its left

hand side. Where f is a structure of a type with i as an element name, the two expressions

f.i and (&f)->i are equivalent.

2.11 Precedence and Order of EvaluationThe following table summarizes the rules for precedence and associativity for the C

operators. Operators listed earlier in the table have higher precedence; operators on the

same line of the table have equal precedence.

Operator Associativity

() [] left to right

! ~ ++ — - (<type>) right to left

* / % left to right

+ - left to right

<< >> left to right

< <= > >= left to right

== != left to right

& left to right

^ left to right

| left to right

&& left to right

|| right to left

= += -= right to left

, left to right


2.12 Control FlowIC supports most of the standard C control structures. One notable exception is the

switch statement, which is not supported.

2.12.1 Statements and BlocksA single C statement is ended by a semicolon. A series of statements may be

grouped together into a block using curly braces. Inside a block, local variables may be

defined. Blocks may be used in place of statements in the control flow constructs.

2.12.2 If-ElseThe if else statement is used to make decisions. The syntax is:

if (<expression>) <statement-1>

else<statement-2>

<expression> is evaluated; if it is not equal to zero (e.g., logic true), then <state-ment-1> is executed.

The else clause is optional. If the if part of the statement did not execute, and the

else is present, then <statement-2> executes.

2.12.3 WhileThe syntax of a while loop is the following:

while (<expression>)

<statement>

while begins by evaluating <expression>. If it is false, then <statement> is skipped. If

it is true, then <statement> is evaluated. Then the expression is evaluated again, and the

same check is performed. The loop exits when <expression> becomes zero.

One can easily create an infinite loop in C using the while statement:

while (1)

<statement>

2.12.4 Do-WhileThe syntax of a do-while loop is the following:

do<statement>

while (<expression>);

The equivalent while loop would be the following:

<statement>while (<expression>)<statement>


2.12.5 ForThe syntax of a for loop is the following:

for (<expr-1>;<expr-2>;<expr-3>)

<statement>

The for construct is equivalent to the following construct using while:

<expr-1>;

while (<expr-2>)

{

<statement>

<expr-3>;

}

Typically, <expr-1> is an assignment, <expr-2> is a relational expression and <expr-3> is an increment or decrement of some manner. For example, the following code counts

from 0 to 99, printing each number along the way:

int i;

for (i = 0; i < 100; i++)

printf(“%d\n”, i);

2.12.6 SwitchThe syntax of a switch block is as follows:

switch (int)

{

case const1:

<statement list1>

break;

case const2:

<statement list2>

break;

default:

<statement list3>

}

The switch construct takes an integer variable as input, and compares it to each

case listed. The first matching const is selected, and execution begins there. The break is

optional, and if no break is found then execution continues through each following state-

ment. Also note that each case has a list of single statements, as opposed to a block

enclosed in curly braces.


Here’s an example of how a switch might be used:

int i = 1;

switch(i)

{

case 0:

printf(“Case 0\n”);

break;

case 1:

printf(“Case 1\n”);

break;

default:

printf(“Default\n”);

}

Since i is equal to 1, the text “Case 1” will be printed to the screen. If i were equal to

0, “Case 0” would be printed. If i were any number besides 0 or 1, “Default” would be

printed.

2.12.5 BreakUse of the break statement provides an early exit from a while or a for loop.

2.13 LCD Screen PrintingIC has a version of the C function printf for formatted printing to the LCD screen.

The syntax of printf is the following:

printf(<format-string>, <arg-1> , ... , <arg-N>);

This is best illustrated by some examples.

2.13.1 Printing Examples

Example 1: Printing a message

The following statement prints a text string to the screen.

printf(“Hello, world!\n”);

In this example, the format string is simply printed to the screen. The character \nat the end of the string signifies end-of-line. When an end-of-line character is printed, the

LCD screen will be cleared when a subsequent character is printed. Thus, most printf state-

ments are terminated by a \n.


Example 2: Printing a numberThe following statement prints the value of the integer variable x with a brief message.

printf(“Value is %d\n”, x);

The special form %d is used to format the printing of an integer in decimal format.

Example 3: Printing a number in binaryThe following statement prints the value of the integer variable x as a binary number.

printf(“Value is %b\n”, x);

The special form %b is used to format the printing of an integer in binary format.

Only the low byte of the number is printed.

Example 4: Printing a floating point number

The following statement prints the value of the floating point variable n as a float-

ing point number.

printf(“Value is %f\n”, n);

The special form %f is used to format the printing of floating point number.

Example 5: Printing two numbers in hexadecimal formatprintf(“A=%x B=%x\n”, a, b);

The form %x formats an integer to print in hexadecimal.

2.13.2 Formatting Command SummaryFormat Command Data Type Description

%d int decimal number

%x int hexadecimal number

%b int low byte as binary number

%c int low byte as ASCII character

%f float floating point number

%s char array char array (string)

2.13.3 Special Notes� The final character position of the LCD screen is used as a system “heartbeat.”

This character continuously blinks between a large and small heart when the board is

operating properly. If the character stops blinking, the board has failed.

� Characters that would be printed beyond the final character position are truncated.

� When using a two-line display, the printf() command treats the display as a single

longer line.

� Printing of long integers is not presently supported.


2.14 PreprocessorThe preprocessor processes a file before it is sent to the compiler. The IC preproces-

sor allows definition of macros, and conditional compilation of sections of code. Using

preprocessor macros for constants and function macros can make IC code more effi-

cient as well as easier to read. Using #if to conditionally compile code can be very useful,

for instance, for debugging purposes.

The special preprocessor command #use has been included to allow programs to

cause a program to download to initiate the download of stored programs that are not in

the IC library. For example, suppose you have a set of stored programs in a file named

“mylib.ic”, some of which you need for your current program to work.

/* load my library */

#use “mylib.ic”

void main()

{

char s[32] = “text string wrapping badly\n”;

fix (s); /* apply my fix function to s and print it */

printf(s);

}

2.14.1 Preprocessor MacrosPreprocessor macros are defined by using the #define preprocessor directive at

the start of a line. A macro is local to the file in which it is defined. The following example

shows how to define preprocessor macros.

#define RIGHT_MOTOR 0

#define LEFT_MOTOR 1

#define GO_RIGHT(power) (motor(RIGHT_MOTOR,(power)))

#define GO_LEFT(power) (motor(LEFT_MOTOR,(power)))

#define GO(left,right) {GO_LEFT(left); GO_RIGHT(right);}

void main()

{

GO(0,0);

}

Preprocessor macro definitions start with the #define directive at the start of a line,

and continue to the end of the line. After #define is the name of the macro, such as

RIGHT_MOTOR. If there is a parenthesis directly after the name of the macro, such as the

GO_RIGHT macro has above, then the macro has arguments. The GO_RIGHT and GO_LEFTmacros each take one argument. The GO macro takes two arguments. After the name

and the optional argument list is the body of the macro.


Each time a macro is invoked, it is replaced with its body. If the macro has argu-

ments, then each place the argument appears in the body is replaced with the actual

argument provided.

Invocations of macros without arguments look like global variable references. In-

vocations of macros with arguments look like calls to functions. To an extent, this is how

they act. However, macro replacement happens before compilation, whereas global

references and function calls happen at run time. Also, function calls evaluate their argu-

ments before they are called, whereas macros simply perform text replacement. For ex-

ample, if the actual argument given to a macro contains a function call, and the macro

instantiates its argument more than once in its body, then the function would be called

multiple times, whereas it would only be called once if it were being passed as a function

argument instead.

Appropriate use of macros can make IC programs and easier to read. It allows

constants to be given symbolic names without requiring storage and access time as a

global would. It also allows macros with arguments to be used in cases when a function

call is desirable for abstraction, without the performance penalty of calling a function.

2.14.2 Conditional compilationIt is sometimes desirable to conditionally compile code. The primary example of

this is that you may want to perform debugging output sometimes, and disable it at other

times. The IC preprocessor provides a convenient way of doing this by using the #ifdef

directive.void go_left(int power){

GO_LEFT(power);#ifdef DEBUGprintf(“Going Left\n”);beep();#endif

}

In this example, when the macro DEBUG is defined, the debugging message “Go-

ing Left” will be printed and the board will beep each time go_left is called. If the macro

is not defined, the message and beep will not happen. Each #ifdef must be follwed by an

#endif at the end of the code which is being conditionally compiled. The macro to be

checked can be anything, and #ifdef blocks may be nested.

Unlike regular C preprocessors, macros cannot be conditionally defined. If a macro

definition occurs inside an #ifdef block, it will be defined regardless of whether the #ifdefevaluates to true or false. The compiler will generate a warning if macro definitions occur

within an #ifdef block.

The #if, #else and #elif directives are also available, but are outside the scope of

this document. Refer to a C reference manual for how to use them.


2.14.3 Comparison with regular C preprocessorsThe way in which IC deals with loading multiple files is fundamentally different from

the way in which it is done in standard C. In particular, when using standard C, files are

compiled completely independently of each other, then linked together. In IC, on the

other hand, all files are compiled together. This is why standard C needs function proto-

types and extern global definitions in order for multiple files to share functions and globals,

while IC does not.

In a standard C preprocessor, preprocessor macros defined in one C file cannot

be used in another C file unless defined again. Also, the scope of macros is only from the

point of definition to the end of the file. The solution then is to have the prototypes, extern

declarations, and macros in header files which are then included at the top of each C file

using the #include directive. This style interacts well with the fact that each file is compiled

independent of all the others.

However, since declarations in IC do not file scope, it would be inconsistent to

have a preprocessor with file scope. Therefore, for consistency it was desirable to give IC

macros the same behavior as globals and functions. Therefore, preprocessor macros have

global scope. If a macro is defined anywhere in the files loaded into IC, it is defined every-

where. Therefore, the #include and #undef directives did not seem to have any appropri-

ate purpose, and were accordingly left out.

The fact that #define directives contained within #if blocks are defined regardless

of whether the #if evaluates to be true or false is a side effect of making the preprocessor

macros have global scope.

Other than these modifications, the IC preprocessor should be compatible with

regular C preprocessors.

��


Chapter 3Interactive C Library

Library files provide standard C functions for interfacing with hardware on the ro-

bot controller board. These functions are written either in C or as assembly language

drivers. Library files provide functions to do things like control motors, make tones, and

input sensors values.

IC automatically loads the library file every time it is invoked. Depending on which

board is being used, a different library file will be required. IC may be configured to load

different library files as its default; IC will automatically load the correct library for the

board you’re using at the moment.

To understand better how the library functions work, study of the library file source

code is recommended; e.g., the main library file for the AX-11 is named lib_hb.ic same

the Handyboard.

For convenience, commonly a description of commonly used library functions follows.

3.1 Commonly Used IC Library Functionsstart_button();

Returns 1 if STRAT button is pressed, otherwise 0.

stop_button();Returns 1 if STOP button is pressed, otherwise 0.

digital();Returns 0 if the switch attached to the port is open and returns 1 if the switch is

closed. Digital ports are numbered 7 to 15. Typically used for bumpers or limit switches.

analog();Returns the analog value of the port (a value in the range 0 to 255). Analog ports

on the AX-11 board are numbered 2 to 6 and 16 to 31. Light sensors and range sensors are

examples of sensors you would use in analog ports.

knob();Returns an int between 0 and 255 depending on knob position.


sleep(<float_secs>);Waits specified number of seconds.

beep();Causes a beep sound.

tone(<float_frequency>, <float_secs>)Plays at specified frequency for specified time (seconds).

printf(<string>, <arg1>, <arg2>, ... );Prints <string>. If the string contains % codes then the <args> after the string will be

printed in place of the % codes in the format specified by the code.

%d prints a decimal number.

%f prints a floating point number.

%c prints a character

%b prints an integer in binary

%x prints an integer in hexadecimal.

motor(<motor_#>, <speed>)Controls the motors.

<motor_#> is an integer between 0 and 3

<speed> is an integer between -100 and 100 where 0 means the motor is off

and negative numbers run the motor in the reverse direction.

fd(<motor_#>);Turns on the motor specified (direction is determined by plug orientation.

bk(<motor_#>);Turns on the motor specified in the opposite direction from fd.

off(<motor_#>);Turns off the motor specified.

ao();Turns all motor ports off.


3.2 ProcessesProcesses work in parallel. Each process, once it is started, will continue until it fin-

ishes or until it is killed by another process using the kill_process(<process_id)>); statement.

Each process that is active gets 50ms of processing time. Then the process is paused

temporarily and the next process gets its share of time. This continues until all the active

process have gotten a slice of time, then it all repeats again. From the user’s standpoint it

appears that all the active processes are running in parallel.

Processes can communicate with one another by reading and modifying global

variables. The globals can be used as semaphores so that one process can signal an-

other. Process IDs may also be stored in globals so that one process can kill another when

needed.

Up to 4 processes initiated by the start_process() library function can be active at

any time.

The library functions for controlling processes are:

start_process(<function_name>(<arg1>, <arg2>, . . .));Start_process returns an integer that is the <process_id> and starts the function

<function_name> as a separate process.

defer();When placed in a function that is used as a process this will cause that process to

give up the remainder of its time slice whenever defer is called.

kill_process(<process_id>);This will terminate the process specified by the <process_id>.


3.3 EncodersThe enable_encoder() library function is used to start a process which updates the

transition count for the encoder specified. The encoder library functions are designed for

sensors connected to (digital) ports 7,8,12 and 13. The corresponding <encoder#> values

are 0,1,2 and 3. Every enabled encoder uses a lot of the AX-11’s processor — so don’t

enable an encoder unless you are going to use it, and never put an enable statement

inside of a loop.

enable_encoder(<encoder#>);Turns on the specified encoder (either 0,1,2, or 3 which are plugged into digital

ports 7, 8, 12, 13 respectively). This should be done only once - never enable an already

enabled encoder. If an encoder is not enabled, read_encoder will always return 0.

disable_encoder(<encoder#>)Turns off the specified encoder.

reset_encoder(<encoder#>)Sets the specified encoder value to 0.

read_encoder(<encoder#>)Returns an int that is the current value of the specified encoder.


3.4 Basic experiment3.4.1 Controlling the DC Motors

To Control the DC Motors, Please ensure that the moors are connected to the MIII

Main board before programming.

3.4.1.1 Procedure(1) Connect the DC Motors to M-0 and M-1 channel on the AX-11 Board.

(2) Make sure the Interactive C Program is opened. Select a NEW Program or con-

tinue with your existing Program.

(3) The Following Sample Code, “DC-CODE” in Listing 3-1, shows how you can control

the DC Motors.

(4) After you have typed / inserted the code, click on the RUN MAIN button.

(5) Observe the Motor Indicator on the LCD Screen.

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/* Example for drive motor *//*Hardware configuration - Motor left connected to DC Motor channel M-0 - Motor right connected to DC Motor channel M-1*/void main(){

while(1) // Infinite loop{

motor(0,50); // Motor0 forward at 50% of maximum powermotor(1,50); // Motor1 forward at 50% of maximum powersleep(2.0); // Delay 2 sec

motor(0,-80); // Motor0 backward at 80% of maximum powermotor(1,-80); // Motor1 backward at 80% of maximum powersleep(2.0); // Delay 2 sec

}}

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3.4.1.2 Results

Observe and you will see the following:

- GREEN LED Lights Up.

- Motor Turns in 1 direction for 2 Seconds

- RED LED Lights Up

- Motor Turns in faster by 30% in another direction for 2 Seconds

This Operation continues in an endless loop.


3.4.2 Controlling RC-Servo MotorsThe Set of servo motors provided in the package can also be programmed to be

run with the main board. The main board’s capability can allow up to 6 servo motors.

In Interactive C, we can use 2 commands. They are

init_expbd_servos();

Represents ON or OFF servo driver circuit : 1 for ON, 0 for OFF

servo = ;

Represents the board servo number, from 0 to 5.

3.4.2.1 Procedure

(1) Connect the RC Servo motor to Channel 0 on the main board. BE CAREFUL OFTHE COLOR CODE.

- WHITE GOES TO S

- RED to +

- BLACK to -

(2) Make sure the Interactive C Program is opened. Select a NEW Program.

(3) The Following Sample Code, “SERVO-CODE” in Listing 3-2, shows how you can

control the Servo Motors.

(4) After you have typed / inserted the code, click on the “RUN MAIN” button.

(5) Observe the Servo Motor’s Operations.

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/* Servo motor test*//*Hardware configuration - servo motor connected to ch-0*/void main(){

int i=600; // Declare and define servo drive valueinit_expbd_servos(1); // Enable servo motor driverwhile(!stop_button()) // Check STOP switch pressed{

servo4 = i; // Drive servo motor ch-4 with servo drive valuesleep(1.0); // Delay 1 seci+=100; // Increase value step = 100if(i>4200) // Check angle>180 deg{

i=600; // Set to origin}

}init_expbd_servos(1); // Disable servo motor driver

}


3.4.3 Controlling the SWITCH SensorThe Main Board allows expandability of up to 9 Digital Inputs.

(1) Connect the Switch sensor to DI-15 ( Digital Input 15) on the Main Board.


(3) The Following Sample Code, “SWITCH-CODE”


(5) Observe the LCD Screen on the Main Board.

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/* Hardware configuration - Touch sensor connected to DI-11 */void main(){

int result; // Declare keep input from touch sensorwhile(1) // Infinite loop{

result = digital(11); // Keep value from DI-11 channelif(result==1) // Check Touch sensor pressed{

printf(“Your press!\n”); // Display message for pressedbeep(); // Sound beepsleep(1.0); // Delay 1 second for display message

}else{

printf(“—————\n”); // Display when Touch sensor not pressedsleep(0.1); // Delay 0.1 second for display message

}}

}

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/*Light Sensor test *//* Hardware configuration - Light Sensor connected to AI-2 */void main(){

int value; // Declare keep input from touch sensor{

value = analog(2); // Keep value from AI-2 channelprintf(“Light = %d\n”,value); // Display Reflect valuesleep(0.1); // Delay 0.1 second for display

}}

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3.4.4 Light DetectionThe Main Board allows 21 Analog INPUTS for analog sensors which converts physi-

cal signals to DC Volts. Light sensors convert physical Light density into DC Voltage. If it is

dark, it’s lower in voltage. If it is Bright, it’s higher in voltage which may exceed 5V.

3.4.4.1 Procedure(1) Connect the Light Sensor to AI-2 (Analog Input 2)


(3) The Following Sample Code, “LIGHT-CODE”


(5) Try these in LIGHT and DARK surroundings.


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3.4.5 GP2D120 ReadingsThe GP2D120 Module sensors are also Analog and therefore use the same ports as

the light sensors. The GP2D120 is not included in AX-11 activity board.

/* GP2D120 test*//*Hardware configuration*/#define base -19float dis_table[118]={ /*distance value*//*ADC value*/32.0,/*19*/ 30.1,/*20*/ 29.5,/*21*/ 28.6,/*22*/ 27.5,/*23*/26.1,/*24*/ 25.3,/*25*/ 24.5,/*26*/ 23.7,/*27*/ 23.2,/*28*/22.3,/*29*/ 22.0,/*30*/ 21.1,/*31*/ 20.5,/*32*/ 20.0,/*33*/19.3,/*34*/ 19.1,/*35*/ 18.4,/*36*/ 17.9,/*37*/ 17.5,/*38*/17.1,/*39*/ 16.5,/*40*/ 16.2,/*41*/ 15.8,/*42*/ 15.6,/*43*/15.5,/*44*/ 15.3,/*45*/ 14.8,/*46*/ 14.2,/*47*/ 13.8,/*48*/13.6,/*49*/ 13.3,/*50*/ 13.1,/*51*/ 12.8,/*52*/ 12.6,/*53*/12.4,/*54*/ 12.2,/*55*/ 12.0,/*56*/ 11.8,/*57*/ 11.7,/*58*/11.6,/*59*/ 11.6,/*60*/ 11.5,/*61*/ 11.4,/*62*/ 11.3,/*63*/10.85,/*64*/ 10.6,/*65*/ 10.3,/*66*/ 10.2,/*67*/ 10.0,/*68*/9.8,/*69*/ 9.7,/*70*/ 9.5,/*71*/ 9.3,/*72*/ 9.2,/*73*/9.0,/*74*/ 8.9,/*75*/ 8.8,/*76*/ 8.6,/*77*/ 8.4,/*78*/8.3,/*79*/ 8.2,/*80*/ 8.0,/*81*/ 7.85,/*82*/ 7.7,/*83*/7.6,/*84*/ 7.5,/*85*/ 7.3,/*86*/ 7.2,/*87*/ 7.15,/*88*/7.1,/*89*/ 7.0,/*90*/ 6.9,/*91*/ 6.8,/*92*/ 6.7,/*93*/6.6,/*94*/ 6.5,/*95*/ 6.4,/*96*/ 6.35,/*97*/ 6.3,/*98*/6.2,/*99*/ 6.15,/*100*/ 6.1,/*101*/ 6.0,/*102*/ 5.9,/*103*/5.85,/*104*/ 5.8,/*105*/ 5.7,/*106*/ 5.65,/*107*/ 5.6,/*108*/5.55,/*109*/ 5.45,/*110*/ 5.4,/*111*/ 5.4,/*112*/ 5.3,/*113*/5.2,/*114*/ 5.1,/*115*/ 5.0,/*116*/ 5.0,/*117*/ 4.9,/*118*/4.9,/*119*/ 4.8,/*120*/ 4.8,/*121*/ 4.7,/*122*/ 4.7,/*123*/4.6,/*124*/ 4.6,/*125*/ 4.5,/*126*/ 4.5,/*127*/ 4.4,/*128*/4.4,/*129*/ 4.3,/*130*/ 4.3,/*131*/ 4.2,/*132*/ 4.2,/*133*/4.1,/*134*/ 4.1,/*135*/ 4.0/*136*/};void main(){

int an; // Keep analog value from sensorwhile(1) // Infinite loop{

an = analog(6); // Read analog value from sensorif(an>=19 && an<=136 ) // Distance interval 10-80 cm{

printf(“dis %f cm adc=%d \n”,dis_table[an+base],an);// Show distance value

}else{

printf(“ Out of Range adc = %d\n”,an); // Show mesage out of Range }

sleep(1.0); // Delay before read new cycle}

}

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3.4.5.1 Procedure

(1) Connect the GP2D120 Sensor to AI-6.

(2) Make sure the Interactive C Program is opened. Select a NEW Program or con-

tinue with your existing Program.

(3) The Following Sample Code, “GP2D120-CODE”


(5) Place an object in-front of the sensor.


(7) Move the object nearer and further from the sensor and observe the LCD Screen

again.

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68hc11 microcontroller activity board with interactive c documentation

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