pic training slide - walkingitaly pic microcontroller microcontrollermicrocontroller ... board for...

1

PIC PIC PIC PIC MicroControllerMicroControllerMicroControllerMicroController TrainingTrainingTrainingTraining

Conduct by : Bill Conduct by : Bill Conduct by : Bill Conduct by : Bill Sim Sim Sim Sim [email protected]@[email protected]@yahoo.com

2

PracticalMicrochip PIC16F877A

Development using MikroC( Software/Hardware)

Date : 28 Aug 08

PICDEM 2 Plus Board

Conduct by : Bill Conduct by : Bill Conduct by : Bill Conduct by : Bill Sim Sim Sim Sim [email protected]@[email protected]@yahoo.com

3

Topics covered

Digital I/O

Hardware interrupt

Timers interrupt

Serial port

Read/Write Internal EEProm

ADC Measurement

LCD display

Pulse Width Modulation - PWM

IIC

Support

Boot loader download

Serial port programmer

External EEProm programming

Real Time Clock

DAC Measurement

QL200 PIC Development Board ( China )

PICDEMO2 Development Board

4

PICDEMO2 PIC Development Board

9V Power

Serial Port

Program download port

LED displayRB4-RB1

Resetbutton

RA4 Button

RB0/Interrupt Button

LCD Display

Analog input RA0

20MHZ Crystal

5

PICDEMO2 PIC Development Board

Interface wiring position

6

General Information

7

Why Need Microcontroller

� Need intelligent in the hardware

� Simplify hardware circuit by firmware

� Easy to modify/upgrade for new requirement

� Use less external components ( e.g. build in Analog-to-Digital converter )

Microcontroller

( Intelligent )Output

(control)

Sensors(Analog/Digital Input)

� Type of microcontrollers:

- Microchip – PIC series such as PIC84, PIC16F877

- Intel – 8051

- Atmel – AT90S8535

- Motorola – 68HC11

- Others

8

Microcontroller

� A single-chip( semiconductor) computer

� Incorporate the supporting chip such memories, input/out, ADC, clock

circuit … into a single chip

� For simple application, it can operate by itself with minimum components.

� Operate on a set of instructions ( “program”). It fetches the instructions from

it program memory , decode the instruction and then execute the required

operation.

� Traditionally programmed by assembly language, but difficult to learn and

maintain. Also assembly language different significantly from controller to

controller.

� High level programming language use are C-language or BASIC

� Mostly are 8 bits , but 16bit or 32 bit microcontroller also available

9

Microcontroller

� Operate in RISC ( reduced instruction set computer) – data is 8 bits, but

instruction word in 12, 14 or 16 bits to allow the instructions to fetch and

execute in one cycle thus speed up the execution process

[ CISC ( Complex Instruction Set Computer) – both data and instructions are

8 bits wide. CISC microcontroller usually has more than 200 instruction.

Code and data are on the same bus and cannot be fetched simultaneously ]

microprocessor

Address decoder

data

addressA

ddre

ss

Inp

uts

/ O

utp

uts

cir

cu

it

Memory bank

Mem

ory

Control signal

Read/write

A microprocessor system

CPUROM

RAM

I /O PortsDigital / ADC / UART … etc

microcontroller

Timer

10

Why use PIC ?

� Supported by C language, BASIC

� Have build in Digital I/O and Analog inputs

� Digital/Analog pins are configurable

� Build in flash program memory, EERPOM data memory and data memory

� Build in oscillator circuit( R/C – low speed ) or external oscillator

� Low power and flexible in supply voltage

� 1K to 32K bytes of flash EEProm program memory

� Timers, interrupts

� 33 input ( Analog/Digital ) or output pin

� Support USART, SPI and I2C

� Operating clock from 4MHZ to 40 MHZ

� Flexible voltage supply from 2V (battery) to 5.5V

11

PIC Microcontroller Architecture

� Power supply – range from 2V to 5.5 Volt. Some may have standby feature

(in uA current) to allow operate by standby battery.

� Power Reset/Reset input – use to reset or initialize the microcontroller

externally. It is connected to an R/C circuit which create a reset pulse at

power up. It also include a push button for user to reset the circuit if required.

� Clock – the heart beat of a microcontroller. Can be internal R/C, external

R/C , crystal (high speed and accurate ). All instruction set execution speed

is a multiple of the clock cycle. For PIC, an instruction cycle takes 4 clock

periods.

� Memory – RAM, Flash EEProm ( program and data memory)

RAM – general purpose memory to store data in a program

Flash EEProm( program memory ) – use to store user program. Nonvolatile

and fast. Can be reprogrammed . Normally range from 1K to 32K or higher

depending on the microcontroller.

Flash EEprom (data memory ) – use to store data that required for next

power up operation. Range from 256 to few Kbytes. Can be programmed by

application software.

12

� Timer/counter ( general purpose ) – a counter that is driven from external or

internal clock. It can be 8 bit or 16 bit and can be software controlled. The

counter initial value can be preloaded. After start counting and reaches

overflow, an interrupt will occur or an internal bit will change state to allow

user to write application. User will then reprogram the counter , do all the

necessary bits reset and start counter/timer again.

� Watchdog timer – use to detect a system problem, such as hang up.

Commonly use in real time system where the successful termination of one

or more activities must be check regularly.


13

� Interrupt – an interrupt causes the microcontroller to response to

external/internal events immediately when it occurs without the need to

check on the events. When interrupt occur, the microcontroller will stop its

normal operation, save up all the required information and go to execute an

special portion of program called interrupt service routine (ISR). After the

execution of the ISR, the microcontroller will resume its normal operation.

For bigger system, there is different level of priority for interrupt from

different devices which can be programmed.

� Brown-out Detector – reset the microcontroller when the power supply

voltage falls below a certain value. This prevents the unpredictable operation

at abnormal power supply and also prevent the EEprom from corrupted.


� Sleep mode

consume minimum power ( in uA ) , only certain intended monitoring is

working to allow the circuit to work with battery. Wake up from sleeping

mode when there is a reset or the monitoring device is activate.

14

� Input/Outputs (build in)

Digital I/Os

Analog to Digital converters

Serial interfaces : UART, SPI, I2C

Pulse Width Modulation output

USB interface

LCD driver

Ethernet interface

Motor controller interface


15

Feature of PIC16F877

8ADC ( 10 bits )

2CCP(PWM)

YesI2C

YesSPI

1 hardwareUSART (Serial Port)

2Comparator

1RB0, 4 in groupExternal Interrupt

2x 8bit, 1x16bitTimers

33I/O Ports

256 byteEEProm

368 byteData Memory

8K x 14 bitProgram Memoryn (Flash EEProm)

PIC16F877AFeatures

16

Pin out of PIC16F877

ADC

Flash

Programing

RS232

Crystal

I2CPWM

Hardware

Interrupt

17

� Programming languages ( in additional to assembly language)

there are two languages : C – language and Basic Language

Recommend to use C- Language for better hardware control.

� Compiler to use

If you choose C-language, you have to use C-compiler

mikroElektronika offer a free ( with size limitation ) and easy to use

compiler with lot of examples.

Design Consideration – Programming Language

18

� Programmer to use

After compiled the program to the Hex code, you need a programmer to

download the Hex code to the microcontroller’s code memory (flash) .

3 methods :

* buy the programmer from the chip suppler

* design your own programmer.

* boot loader method

Design Consideration – Program Download

the programmer uses USB as interface to the PC.

Application program is provided for

downloading program from PC to the PIC

microcontroller.

Buy programmer PICkit2 from Microchip company

It come with the hardware and software. There is also another development

board for starter using 16F690 that you can use in conjunction with this

programmer.

19

Software

After you have the hardware made, you need to have the programmer’s

software. A free software called WinPic is the best programmer software

found so far. You can download from the following site :

http://www.nthkits.com.sg

Design your own programmer ( hardware & software )

Hardware

there are many information on internet on how to design the serial

programmer for the PIC. A simple one is to use PC’s serial port where you

suppose to get 12V from the serial port pin to program the PIC.

A slightly complicated one is to use external power adapter to provide the

12V but still use serial port for this purpose. This is useful if some PC does

not give you stable 12V


20

Boot loader method

�boot loader is a small piece of firmware that reside inside a

microcontroller’s code memory and is responsible for downloading future

application firmware developed to the microcontroller

�PIC product to use is 16F877A and above

�the boot loader and its application program used is FREEware

�boot loader firmware have to be pre-programmed only once using standard

programmer

�use serial port to download the application firmware developed

�crystal use is 20MHZ, baud rate of the serial port is 38400bps

�Boot loader’s application program , called PICdownloader, is installed on a

PC for downloading purpose

�Select the Hex file to be download, com port and the baud rate and click the

“write” button.

�Power OFF/ON the board and the firmware will be downloaded into the

controller


21

Boot loader method

http://www.microchipc.com/PIC16bootload/index.php

Reset the target board


22

Digital I/O Port A/B/C/D/E

PIC 16F877ADigital IO

A EB C D

23

Digital I/O

Your will learn :

Hardware

How to program digital I/O ports and application

How to use push button Switch and eliminate debounce

How to flash LEDs

Software

How to output byte data to hardware port

How to handle bit wise ( Input/Output ) for a hardware port

How to use delay_ms subroutine

How to make human readable flashing

24

� PortA and PortE can be configured as Digital IO or Analog input (ANx)

� Two registers need to be configured : ADCON1(A/D control register) and

TRISA(data direction register)

� Analog pins need to define as input pins

PortA/E Configuration

ADCON1Register

TRISA/ERegister

Define Digital or analog pin

Define input or output pin

PortA/E pins

Digital input or

Digital output or

Analog pin

Bits configuration

� To define portA as all digital IO,

ADCON1 = 0x06;

� To define portA as all output pins

TRISA = 0x00;

� To define portA as all input pins

TRISA = 0xff;

For RA0 to RA3, RA5, RE0 to RE2

Note : RA4 is open collector pin

25

� The configuration table for ANCON1 is shown below :

only the first 4 bits is used

ANCON1 Configuration

26

� PortA/B/C/D/E can be configured as Digital IO via data direction

registers TRISA, TRISB,TRISC , TRISD & TRISE

PortA/B/C/D/E Configuration

TRISXRegister

Define Digital or analog pin for PORTA/B/C/D/E where X = A or B or C or D

Digital input or

Digital outputBits configuration

For example ,to define Port D , bit 0 to 3 as digital input and bit 4 to 7 as

digital output, TRISD = 0x0f;

27

Some C Programming statements

�Write to a port or register byte wise

TRISB = 0xff;

PORTB = 0x0a;

�Read from a port or register byte wise

If ( PORTB = = 0x38 ) { … }

�Write to port or register bit wise

PORTB.F1 = 1; // bit 1 of PORTB

�Read from a port or register bit wise

If ( PORTB .F0 = = 0 ) { … }

If ( ( PORTB & 0x01) == 0x00 ) { … }

�Complement a port

PORTB = ~PORTB ; // 1 become 0 , 0 become 1

MikroC Statements

28

Some C Programming statements

�Delay time in milliseconds

delay_ms (int number); e.g. delay_ms(500);

�Delay time in microseconds

delay_us(int number); e.g. delay_us(200);

�Variable delay time in milliseconds

int mydelay;

mydelay = 300;

Vdelay_ms( mydelay);

MikroC Statements

29

Interrupts

•Hardware Interrupt

•Timer0 Interrupt

•Multiple Interrupt

30

Your will learn :

Hardware

What is hardware interrupt

How use hardware interrupt in 16F877A

Parameters that need to consider for interrupt

Software

How to write interrupt service routine

How to program INTCON & OPTION_REG registers

Timer 0 interrupt

How to handle multiple interrupt

Hardware Interrupt

31

� Interrupt is used to reduce the workload of the CPU. A special job will

only be done when the interrupt occurs. This special job is placed as part

of the software program called interrupt service routine (ISR) . CPU will

perform its normal operation till an interrupt occur. When it happens, the

CPU will stop its normal operation, save up all the registers and then

execute the interrupt service routine till its completion. It will then back

to its normal operation.

� When enter into ISR, it is a good practice to disable the interrupt . This is

to prevent response to another interrupt when the previous ISR has not

completed yet. Before exit the ISR, the interrupt need to be enabled and

ready for another hardware interrupt.

Interrupt

� For 16F877A, there are 3 user defined interrupts ( in additional to

16F877’s standard peripheral interrupts). They are :

hardware interrupt ( RB0/INT) , Timer0 interrupt and RB4-RB7 group

interrupt

� Other interrupt provided for the feature of 16F877 is called peripheral

interrupt and is important for assembly language or C – library

programmer

32

Perform specialJobs (interrupt

Service routine )

uControllerperforming normal

operation

Interrupt Flow Chart

InterruptOccurs ?

Disable interrupt/ Save all current jobs

Completed ?

Enable interruptResume current jobs

N

Y

Y

Start

Interrupt

N

ISR

33

� registers that involved in the interrupt operation, INTCON (0x0b) register

and OPTION_REG (0x81)

Hardware Interrupt

GIE - Global Interrupt Enable bit

INTE – RB0/INT External interrupt enable bit

INTCON (0x0b)

GIE PEIE T0IE INTE RBIE T0IF INTF RBIF

Bit 0Bit 7 Default : 0000 000x

� INTCON bit 3, known as RBIE, if set to 1, will inform PIC that RB4 to RB7

will be used as interrupt input group. They can not be select individually.

� When interrupt occurs, the interrupt flag , bit 1 of INTCON register is set.

When this occur, the PIC microcontroller will not respond to any further

interrupt .

Enable occur

34

INTCON Register (0x0b)

For External interrupt RB0/INT

GIE PEIE T0IE INTE RBIE T0IF INTF RBIF Bit 0Bit 7

Default : 0000 000x

Enable Occur flagGlobal Interrupt Enable bit

For timer-0 (TMR0) - interrupt

For peripheral interrupt RB7 – RB4 (all) as interrupt

Hardware Interrupt

35

� The Peripheral interrupt enable bit ( PEIE ) have to work with another two

sets of interrupt enable registers and flag for a specific features provided by

PIC 16F877 . they are :

PIE1/ PIR1 for

Parallel Slave Port Read/Write Interrupt (PSPIE)

A/D Converter Interrupt (ADIE)

USART Receive Interrupt ( RCIE)

USART Transmit Interrupt (TXIE)

Synchronous Serial Port Interrupt (SSPIE)

CCP1 interrupt (CCP1IE)

TMR2 to PR2 Match Interrupt (TMR2IE)

TMR1 Overflow Interrupt (TMR1IE)

Hardware Interrupt


36

� PIE2/ PIR2 for

Comparator Interrupt (CMIE)

EEPROM Write Operation Interrupt (EEIE)

Bus Collision Interrupt (BCLIE)

CCP2 Interrupt (CCP2IE)

� The C language function library provided by vendor will take care of all

these standard feature interrupt. We will focus on non-peripheral related

interrupts.


Hardware Interrupt

37

� Option register ,OPTION_REG, bit 6 , INTEDG ( Interrupt Edge), when

set, will cause the PIC to be interrupt on rising edge. When clear, the PIC

will be interrupted on falling edge. The default interrupt setting is on rising

edge.

Hardware Interrupt

INTEDG = 1 INTEDG = 0

RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0

Bit 0Bit 7

INTEDG – Interrupt Trigger Edge

OPTION_REG (0x81)

Default : 1111 1111

� When PB4 to PB7 are used as interrupt ,

you cannot select individual pins on

PORTB to serve as an interrupt input. It

may be not so practical to use them as

interrupt as you can not make use of these

pin as I/O.

RB0/INT

INTEDG = 1 INTEDG = 0

38

� Option register ,OPTION_REG, bit 7 , RBPU, when clear (=0), will turn on

PORTB’s internal pull-up (weak) as a ‘high’. The respective internal pull-up

of the PORTB’s pin will automatically turn-off when the PORTB’ pin is

assign as output.

Hardware Interrupt


Bit 0Bit 7

OPTION_REG (0x81)

Default : 1111 1111

16f877

RB0

5V

Depending on circuit designed

/RBPU = 0

39

OPTION_REG Register (0x81)

RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 Bit 0Bit 7

Default : 1111 1111

� OPTION_REG register contains various control bits to configure the TMR0

prescaler / WDT postscaler, external interrupt(RB0/INT), TMR0 and weak

pull up on PORTB

Prescaler

PORTB pull-up

RB0/INT interrupt

edge type

TMR0 Clock source

TMR0 Source

edge type

Prescaler assign to

WDT or Timer0

Prescaler rate select

Hardware Interrupt

40INTEDG = 1 INTEDG = 0


Bit 0Bit 7

INTEDG – Interrupt Trigger Edge

OPTION_REG (0x81)

Default : 1111 1111

Hardware Interrupt

OPTION_REG Register (0x81)

41

Some MikroC Programming statements

Hardware Interrupt

INTCON.F7=1; //enable global interrupt

INTCON.F6=1; // enable all peripheral interrupt

INTCON.F4=1; //set PB0 as the external interrupt

OPTION_REG.F6=0; //interrupt at negative edge

OPTION_REG.F7=0; //turnon RB0's internal pullup (weak)

void interrupt() // funciton name of interrupt service routine

{

INTCON.F4=0; //disable RB0/INT

… ISR jobs …

INTCON.F1=0; //MUST HAVE -- clear interrupt flag

INTCON.F4=1; //enable global interrupt

}

Hardware Interrupt

42

Timer Interrupt

43

� Timer0 , TMR0, is a 8 bit binary up counter

� Count driven by external or internal clock source.

� TMR0 register stores the counter value which can be reset or preloaded

with value

� Count increase with each input pulse until TMR0 overflow

(from 0xFF to 0x00)

� Overflow triggered timer0 interrupt. The interrupt service routine will then

be executed.

Timer Interrupt

44

� TMR0 register and prescaler relationship

Timer Interrupt

Load TMR0=0Prescale

Set RB1=~RB1Load TMR0=0

After 255 Pulse by timer0

d

For a 20MHZ crystal,

d= ((# of tick) * 4 * Prescaler * 1000 )/(clock frequency)

Case 1 : Prescaler = 1

d = 255 * 4 * 1 * 1000 / 20 000 000 = 51 usCase 2 : Prescaler = 1:2

d = 255 * 4 * 2 * 1000 / 20 000 000 = 102 usCase 3 : Prescaler = 1

d = 255 * 4 * 256 * 1000 / 20 000 000 = 13.6msCase 4 : Prescaler = 1

d = 95 * 4 * 256 * 1000 / 20 000 000 = 4.86 ms

d

Interrupt

45

Multiple Interrupts

46

Multiple Interrupt

� When there is multiple interrupt requirement , the interrupt service function

must check for what interrupt has happen and then execute the respective

interrupt handler. E.g. RB0/INT or TMR0 handler

� The INTCON_REG provide the flag of the interrupt.

GIE PEIE T0IE INTE RBIE T0IF INTF RBIF Bit 0Bit 7

INTCON_REG

47

Some MikroC Programming statements

Timer Interrupt

OPTION_REG = 0x18; // Prescale to WDT i.e TMR0 no prescale

void rb0_interrupt(void)

{ … jobs here …}

void tmr0_interrupt(void)

{ … jobs here …}

Multiple Interrupt

void interrupt() {

INTCON.F7 = 0; // disable further interrupt

if ((INTCON & 0x02)==0x02){rb0_interrupt(); } // check for hardware interrupt

if ((INTCON & 0x04)==0x04){tmr0_interrupt();} //check for timer0 interrupt

INTCON=0xf0; //enable global and the required interrupt

}

Multiple Interrupt

48

USART (Serial / RS232) Communication

49

� USART stands for Universal Synchronous Asynchronous Receiver

Transmitter

� RS232, Serial Port, COM Port … means the same thing

� Most of the desktop PC & engineering instrumentation still support

serial port

� Its family standard RS422 can connect many devices together using 3

wires

� For PIC 16F877, USART is access through RC7 for Receive and

RC6 for Transmit at TTL level ( hardware USART )

� A RS232 line driver need to interface with RC7/RC6 to deliver the

RS232 standard (i.e. high voltage level for long distance driving ) via

a Max232 chip.

Refer to any standard RS232 article for more detail description

USART/Com port/ Serial Port

50

� RC6/RC7 provide signal at TTL level. MAX232 converts TTL high

level to -13V and TTL low level to +13V which is good for data

transmission on long wire.

� When No transmission, the signal is “high”, start bit is “low” , Stop

bit is “high”

16F877Acircuit

RC6

RC7 MAX232(1/2)

RS232

Start bit (0)

D0 D1 D7

Stop bit (1)

t

v

Hardware USART

51

� MikroC support both software USART and hardware USART

Software USART commands

� soft_Uart_Init ( port-number, rx-pin, tx-pin, baud rate, mode)

mode = 0 : data not inverted

e.g Soft_Uart_Init( PORTB, 0,1, 9600,0); PB0 – rx, PB1-tx

� Soft_Uart_Read(&Rx_Error)

e.g do {

mychar = Soft_Uart_Init(&Rx_Error);

} while (Rx_Error);

error is normally 1 and become 0 when a byte is read from the port

� Soft_Uart_Write( character ); e.g. Soft_Uart_Write(‘A’);

MikroC Statements

52

Hardware USART Commands

� Hardware USART can support higher baud rate

� Parameters need to setup for communication – only baud rate is needed

Baud rate : 38400 or others supported baud rate

Rest of parameters are set, by the MikroC as follows :

number of data bit : 8 bits

number of stop bit : 1

Parity bit : N ( no parity )

e.g. USART_init(38400);

� 4 C-statements involve in serial communication

Char USART_Write(char data) - 1 byte

Char USART_Read(Void)

Void USART_init( const long baudrate)

Char USART_data_ready(void)

MikroC Statements

53

Read/Write Internal Data EEProm

54

� 16F877 has 256 byte of data memory and 8K of program memory that

allow data and program remain in the device when power of switch off.

� The 6 SFR ( Special Function Register) use to support these functions are :

EECON1, EECON2( Not a physical register ), EEDATH: EEDATA

( Holds 14 bits of data for Read/Write ) and EEADRH:EEADR ( holds

the 13 bit address of the program memory location being access ).

Read/Write to Internal Data EEProm

55

Read/Write to Internal Data EEProm

56

� In MikroC, to write and read to internal EEProm, use the following

statements :

Unsigned short eeprom_read(unsigned short address);

e.g. char read_data;

read_data = eeprom_read(0x30);

void eeprom_write(unsigned integer address, unsigned short data);

e.g. eeprom_write(0x30, 0x11);

MikroC Statements

57

LCD Display

58

LCD Display

PIC 16F877A

LCD

RD7-RD3

RA1 - RS

RA2 - R/W

RA3 - E

� The interface to LCD display is done through a set of data bit and control bits

� For the demo circuit, it uses 4 bits, RD7-RD3, for data instead of full 8 bits

� For MikroC, there is a predefine hardware interface as specified in the

programming manual page 241, all LCD pins must connected to a single port.

� If you are using different hardware connection, normally the case, you can use

the programming generator ( or you can write your own code ) provided by

MikroC to generate the functions required to program the LCD based on your

hardware connection (e.g. see below)( called LCD4 Optimum Module by Warren Schroeder April 25, 2007 )

59

MiKroC’s LCD Library’s hardware requirement

PIC 16F877A

LCD

RB2-RB5

RB0 - RS

RB1 - E

Lcd_Config (port-name, RS-pin, EN-pin, R/W-pin, D7-pin, D6-pin, D5-pin, D4-pin)

R/W-pin is not use, should connect to ground (always write)

e.g. Lcd_Config ( &PORTB, 0,1,2,3,4,5)

Lcd_Init(Port-name ); Lcd_Init(&PORTB);

Lcd_Out(row, column,text); Lcd_Out(1,2,”MyTest”);

Lcd_Out_Cp(text); Lcd_Out(“Hello); output text from the Current Position

Lcd_Chr ( row, column, character); Lcd_Chr(1,2,’M’);

Lcd_Chr_Cp(character); Lcd_Chr_Cp(‘M’);

All pins must within a Port.

Otherwise cannot use the library

LCD Display

60For PICDEM2

Use when the LCD

interface pins involve more

than one PORT

�Select PIC type

�Define RS pin connection

�Define E pin connection

�Define Data pins ( 4 pins)

connection

�In the software, set

always write mode

( PORTA.F2 = 0 for /W )

Program Generator

LCD Display

61

LCD Application Constant

Lcd_Cmd(command constant);

LCD_SHIFT_RIGHT

LCD_SHIFT_LEFT

LCD_MOVE_CURSOR_RIGHT

LCD_MOVE_CURSOR_LEFT

LCD_TURN_OFF

LCD_TURN_ON

LCD_BLINK-CURSOR-ON

LCD_FORTH_ROW

LCD_THIRD_ROW

LCD_SECOND_ROW

LCD_FIRST_ROW

LCD_RETURN_HOME

LCD_CLEAR

Command constant

62

Analog Measurement

(Analog-to-Digital Converter)

63

Purpose of ADC

� To measure an analog voltage (e.g. sensor) input and convert to digital

for the micro-controller to interpret and make decision

� Sensor/transducer produced very small analog voltage . In some cases it

could be uV ( micro-volt ) and it needs an analog amplifier to amplify

the signal to a measurable analog voltage.

� In order for a computer/microprocessor/micro-controller to interpret the

analog signal, the analog signal need to convert to digital , for at least 8

bits or more. ( 10 bits for PIC16F877 )

� If the analog signal is small, you have to use lower Vref in PIC16F877

ADC measurement in order to get more accurate digital measurement

Sensor A ADC

64

ADC Block Diagram

AN7

AN6

AN5

AN4

AN3

AN2

AN1

AN0

CS2-CS0

ADC Converter

Verf+

Reference Voltage

Verf-

VSS

VDD

10 bits

PCFG<3:0>

65

ADC setup

AN0

AN1

VDD

VDDVSS

VSS

16F877

2

3

� 3 Registers involve in the ADC Operation : TRISA , ADCON1 and

ADCON0

Vref

Vref can be VDD or other value

AN7 AN2AN6 AN5 AN3 AN1 AN0AN4

RE2 RA2RE1 RE0 RA3 RA1 RA0RA5

Symbol

Hardware port

V = (bits value) *(Vref / 1024)

When measure small voltage , it is more accurate to supply own Vref

Due to VDD may vary , it is more accurate to use a Vrefinstead of using VDD as Vref

10 bits ADC converter

66

What need to be set for measurement ?

� How many analog ports to use and Vref to use : PCFG3-PCFG0 in

ANCON1

� Set the respective hardware ports to be input for ADC operation

TRISA and/or TRISE

� Define measurement data to be read is Right justify or Left justify

ADFM bit in ANCON1

� Select AD conversion clock : ADCS2 in ANCON1 and ADCS1 &

ADCS0 in ANCON0( A/D control register 0)

� For each channel to be measured, select the channel number and set

ADC to be ON : CHS2-CHS0 bits and ADON bit in ANCON0

� For each channel selected, set the GO//Done bit in ANCON0 to “1”

and start ADC measurement. When ADC measurement completed,

the GO//Done bit will be set to “0”. 10us Conversion time should be

sufficient ( refer to data sheet for detail calculation)

67

� When use AN0 & AN1 as input, from the configuration table, select PCFG3

to PCFG0 to be 0100

Analog to Digital conversion setup

ADCS1GO//Done

ADCS0 CHS2 CHS1 CHS0 - ADON ADCON0

ADFM PCFG2ADCS2 - PCFG3 PCFG1 PCFG0

ADCON1

-

Select AD conversion clock

110 = FOSC/64 for 20MHZ crystal OK

Right justify

ADRESH,ADRESL = 000000xx,xxxxxxxx

1

1

Select channel 0

1Enable A/D measurement

AN0 ,AN1,AN3– analog, AN2, AN4 – AN7 all digitalVREF+ = VDD, VREF = Vss ( internal )

TRISA = 0x0b; PortA0, PortA1 & PortA3 are inputs, PortA2, PortA4 – PortA7 are outputs

= 1 Start A/D conversion=0A/D conversion completed

1 0 0 0 0

0 1 0 0

68

� The configuration table for ANCON1 is shown below :

only the first 4 bits is used


69

� When ports are selected for analog input, the conversion clock rate ( use in

conjunction with ADCON0 ) and the ADC read result format are set

according to the following format :


70

ADCON0 Configuration

ADCON1ADCON0

71

/* Read AN1 port , use FOSC/64 */

ADCON0= 0x89; // importnant : switch port first, don't measure

delay_ms(100); // important : for it to stabilize

ADCON0 = 0x8d; // AN1 read

delay_ms(100);

while( ADCON0 & 0x04){} // check conversion completed ?

dataL= ADRESL; // read result

dataH=ADRESH;

write_ADC_result(dataH,dataL); // output result to display

Important ADC Program

ADC Measurement Steps

72

Pulse Width Modulation

73

� PWM stands for Pulse Width Modulation

� PWM is basically sending a pulse with various duty cycle so the receiver

device, which is a PWM operated, can perform a specific function.

Example : Servo motor, beeper, flash light …etc


� When the pulse width is longer, the flashing LED will be brighter or the

beeper will have different sound frequency. For PWM servo motor, the

motor will turn in different direction.

� PWM pulse can be generated by pulse a output pin the “Hi” & “Lo” with

time delay to generate the pulse or can be done by a specific PWM output

pins

� For 16F877, it has two pins RC1 ( CCP2 ) and RC2 (CCP1) that response

to generate the PWM pulses

w

T

Duty cycle = W / T * 100%

74

In MiKroC the statements use to generate the PWM are follows :

� void PWM_Init(long freq); - initialize PWM frequency

void PWM_Change_Duty( char duty_ratio ); - set duty cycle

where duty_ratio ranges from 0 to 255

duty cycle = ( % * 255 ) / 100

50% duty cycle , duty_ratio = 127

100% duty cycle, duty_ratio = 255

� void PWM_Start (void) ; - start PWM

� void PWM_Stop (void); - stop PWM

� For 16F877 chip, there is two PWMs, you can use PWM1 and PWM2

syntax to generate two different PWM pulse


75

PWM1_Init(5000);

PWM2_Init(5000);

PWM1_Change_Duty(127); // 50% duty cycle

PWM2_change_Duty(20); // 7.84% duty cycle

PWM1_start();

PWM2_start(); // determine PWM to start

while( PORTA.F4 == 0){} // when button release, stop

PWM1_stop();

PWM2_stop();

RC1 ( CCP2- PWM2 ) RC2 ( CCP1- PWM1 )


In MiKroC the statements example

76

� For motor control, pulses with various duty cycle are used for DC Motor

speed control and servo motor position control

� For servo motor position control, different pulse width will cause the

motor to rotate at different angle.

� The general guide line for servo motor rotation are as follows :

PWM for Servo Motor Control

1 ms

18 ms

Left

1.5 ms

18 ms

center2.0 ms

18 ms

right

77

IIC Serial Communication

78

� System level serial data communication method

� Need two signal lines : data (SDA) and clock (SCL)

� Allow a master device control up to 1023 other devices

� Signal lines have 5V pull up

� Each data bit is accompany by a clock pulse

� Clock speed is programmed by preload the baud rate generator up to 1MHZ

7 6 5 4 3 1 02

5V

Master Slave Slave

4.7K

4.7K

acknowledgementstart

SDA

SCL

SDA

SCL


79

Interface to a 256K EEProm


16F877Acircuit

RC4

RC3

SDA

SCL

5V

A2

A0A1

SDA

SCL

5

6

8

4

24LC256

256K IIC Serial EEProm

5V

4.7K

4.7K

80

In MiKroC the statements use in IIC communication are follows :

� void I2C_Init(long clock);

� char I2C_Start(void);

� void I2C_repeated_Start(void);

� char I2C_Is_Idle(void);

� char I2C_Rd(char ack); ack=0 means no acknowledge

� char I2C_Wr(char data);

� void I2C_Stop(void);


81

…

I2C_Start();

I2C_Wr(0xA0); //control byte for write

I2C_Wr(addrhighbyte); //address to write - high byte

I2C_Wr(addrlowbyte); //address to write - low byte

I2C_Wr(data); //data

I2C_Stop();

…

Write Byte


82

…

I2C_Start();

I2C_Wr(0xA0); //control byte for write

I2C_Wr(addrhighbyte); //address to read high - byte

I2C_Wr(addrlowbyte); //address to read low - byte

I2C_Repeated_Start();

I2C_Wr(0xA1); //control byte for read

data = I2C_Rd(0u);

I2C_Stop();

…

Random read address


83

Read/Write External EEprom93LC46 using I/O Ports


84

16F877Acircuit

93LC46

RC2

RC4

Functional block diagram

RC3RC5

CS

DO

CLKDI

VCC

VSS

NCNC

Parameters:

38400

8 data bits

1 stop bit

N parityMemory locations to write/read are :

0x01, 0x02 ,0x3f ,0x18 ,0x2a

External EEprom – using I/O

85

� 93LC46 is a 1024-bit non-volatile, serial EEProm.

� 6 bit of address and 16 bit of data –> total = 64 x 16 = 1024 bit

� 4 signal pins : CS – chip select, SK – clock pin, DI – data in,

DO-data out.

� Provide write enable or disable function to protect the data

� All functions such as read, write, write enable … etc required a

predefine function header before the address and/or data – see

datasheet for detail

� Write data to a address – provide 6 bits of address follow by 16 bits

of data to the DI pin

� Read data at address – provide 6 bit of address and read data from the

DO pin

� 4 important functions : Write enable, write disable, read and write


86

Write enable

Write disable

Pin Layout


87

Write data operationmust have


88

Read data operation


89

� Program Methodolgy

� DI1, DI0 – input data bit high, low

� CS1, CS0 – chip select bit high, low

� Clk - generate 1 clock pulse

void CS1(void) { PORTC.F2=1; delay_us(200); }

void CS0(void) { PORTC.F2=0; delay_us(200); }

void DI1(void) { PORTC.F5=1; delay_us(200); }

void DI0(void) { PORTC.F5=0; delay_us(200); }

void clk (void) {PORTC.F3 = 0; delay_us(100);PORTC.F3 = 1; delay_us(200);PORTC.F3 = 0; delay_us(100);}


90

Real Time Clock


91

Your will learn :

Hardware

Function of Real Time Clock

Software

How to program the Real Time Clock :

Write Date and Time

Read Date and Time

Protect / Un-Protect RTC for writing

Real Time Clock (RTC)

92

� Program the date and time with the following information :

Date : 23 /07/08 Time : 14:50:00

� Read back the Date and time every seconds and display on LCD and on serial port

Real Time Clock Project

16F877Acircuit

RTC DS1302

RB0

RB4RB5

CLK

I/ORST

Parameters:

38400

8 data bits

1 stop bit

N parity

Date:23/07/08Time:14:59:20

LCD Display


93


� RTC counts Hour:Minute:Second and Day/Month/Year with other features

such as 12/24 hour, AM/PM option

� RTC used here is DS1302, 8 pins IC(3 signal wires), 2V to 5.5V operation

� RTC chip need to work with an crystal oscillator circuit (32.768kHz)

� RTC also provide serial interface for data I/O ( read/write ) and clock

� Two power supplies input for RTC, One for battery and one for normal DC

power

� Date and Time is set through the programming to a set of predefine memory

location with the desire Date and Time value in “human understandable”

value. These value are written directly to the memory location in “HEX”

format without conversion to hex value.

e.g. 14 hr, 20 min, 59 sec write as 0x14, 0x20 and 0x59

94


� Memory locations for writing and reading of Date and Time

Location

for read

Location

for write

Max = 5 ,need 3 bit Max = 9 , need 4 bit

95

Digital to Analog Converter

TLC5615C


96


TLC5615C

10 bit CMOS voltage output DAC

3 wire interface

High impedance reference input

8 pin package

97


� To program the TLC5615C , need to send 16 bits of serial data into the

shift register of TLC5615C

� Only 10 bits are for voltage programming :

Vout = 2 * (V ) * refin

V

1024

10 bits

L7 L6 L5 L4 L3 L2 L1 L00 0 0 0 0 0 H1 H0

Vout = 2 * (2) * V

1024

(01 10101011)

If Vrefin = 2.0v, VH = 0x02 VL= 0xab;

VH – High byte VL – Low byte

Vout

= 4 * (683/1024)

= 2.67 v

98


� The bit pattern send to the TLC5615C serially are :

0,0 ,L0,L1,L2,L3,L4,L5,L6,L7,H0,H1,D,D,D,D

where D – dummy bit, 0 - zero

� Every data bit will send to the TLC5615C when the clock is at high

transition.

� /CS must be “low” before the first clock take place and must be “high”

after the last 16th bit is clocked.

99


100

Digital to Analog Converter Project

PIC 16F877A

To advance the DAC output to different value

RC2 - CS

RC3 - SCLK

RC5 - DIN

RA0

RB0

RB7

Lowest 8 DAC bit to PORTB display

REF In = VDD

TLC 5615D/A

VOUT


101


� Programming sequence are :

/CS = 0

send in 4 clock pulse ( Din don’t care – dummy )

Reverse the bit sequence for High byte and low byte

for each of the 10 bit ( high or low ), send in the clock to clock in the bit

send in two clock with DIN= 0

/CS = 1

102

Some Useful Functions

103

Read the eeprom addressEEProm_read (address)

Write the eeprom address with the dataEEProm_Write (address, data)

Software delay using program variableVdelay_ms ( variable)

Software delay in millisecondsDelay_ms (number)

Software delay in microsecondsDelay_us (number)

Return (bit 31-24 ) of a numberHighest (number)

Return ( bit 23- 16 )of a numberHigher (number)

Return ( bit 15- 8 ) of a numberHi (number)

Return ( bit 7- 0 ) of a numberLo (number)

Descriptionfunction

Useful functions

104

Concert a character to lowercaseTolower

Convert a character to uppercaseToupper

Return a 1 if is is uppercaseIsupper

Return a 1 if is is printable ( decimal 32-126)Isprint

Return a 1 if is lowercaseIslower

Return a 1 if is 0-9Isdigit

Return a 1 if is control character ( decimal 0-31 and 127)Isntrl

Return a 1 if it is a-z, A-ZIsalpha

Return a 1 if is alphanumeric ( a-z. A-Z, 0-9)Isalnum

Descriptionfunction

Useful functions

105

Return the absolute valueAbs

Convert ASCII character to floating point numberAtof

Convert ASCII character to integerAtoi

Convert ASCII to long integerAtol

Return the greater of two integersMax

Convert input string consisting of hex digits into integerXtoi

Generate a seed for function rand to callSrand

Return a random number between 0 and 32767. srand() must be called firstRand

Return the lesser of two integersMin

Descriptionfunction

Useful functions

106

Return the length of a stringStrlen

Copy one string into another oneStrcpy, strncpy

Compare two stringsStrcmp, strncmp

Locate the first occurrence of a character in a stringStrchar, strpbrk

Append two stringsStrcat, strncat

Descriptionfunction

Useful functions

107

Convert a decimal number into BCDDec2Bcd

Convert a BCD number into decimalBcd2Dec

Convert a float into stringFloatToStr

Convert a long into stringLongToStr

Convert an integer into stringIntToStr

Convert an unsigned word into stringWordToStr

Convert a short into stringshortToStr

Convert a byte into stringByteToStr

Descriptionfunction

Useful functions

109 [email protected]

pic training slide - walkingitaly pic microcontroller microcontrollermicrocontroller ... board for...

Documents