ms_uc / fue1 / v01 1 usb programming microcontroller universal synchronous bus (usb) autumn 2012

MS_uC / fue1 / V01

1

USB

Programming MicrocontrollerUniversal Synchronous Bus (USB)

Autumn 2012

MS_uC / fue1 / V01 Overview (story)USB

2

1995: Foundation of the “USB Implementers Forum” (USB IF) http://www.usb.org

1996: First USB specification issue (USB 1.0)

Connection of various peripheral devices to a single interface Mouse, keyboard, printer …

2000: Specification of USB 2.0 Extension of the speed at 480 M bit/s Possibility to connect hard drives or video devices

MS_uC / fue1 / V01 Overview (generality)

USB is a asymmetrical bus Distinction between USB host (PC) & device

Data is transmitted in a serial asynchronous format

Baud rate 1.5 M bit/s (Low-Speed) 12 M bit/s (Full-Speed) 480 M bit/s (High-Speed, only for USB 2.0)

USB

3

MS_uC / fue1 / V01

4

USB bus topology (network)

127 devices can be connected to the bus (incl. hubs) Each USB device receives a specific address from the

host (PC) Enumeration Host

Root-Hub

Hub

Hub

Device 1

Device 2

Device 3 Device 4

1 2

3 4

5 6

USB

4

MS_uC / fue1 / V01 USB bus topology (power supply)

Bus powered hub The total current is obtained from the host (PC) 500 mA are available for the all the connected devices

Self powered hub Additional connector for the power supply Each device can consume a maximum of 500 mA

USB

5

MS_uC / fue1 / V01 USB cable

USB cable contains 4 wires VCC (+5V) GND Differential data lines D+ and D- (0 and 3.3 V)

Signal rise and fall times www.usb.org

USB

6

MS_uC / fue1 / V01

7

USB plugs

Function

Host Pin-Nr(Type A)

Device Pin-Nr(Type B)

Device Pin-Nr

(Mini USB)

Color

VCC (5V) 1 1 1 red

D - 2 2 2 white

D+ 3 3 3 green

GND 4 4 5 black

ID - - 4 Not connecte

d

USB

7

MS_uC / fue1 / V01 USB speed detections (1/2)

Full & high speed Devices Low speed Device

Host / hub must recognize the connected USB device

Host / hub begins with the speed detection Pull-up or pull-down resistors

8

MS_uC / fue1 / V01 USB speed detections (2/2)

Distinction between full & fast speed devices Full speed devices generate a chirp signal (fast toggling)

during reset Host recognize this chirp and switch into high speed Pull-up resistor is disconnected during this transmission mode

4- 9

UART - Serial communic.

MS_uC / fue1 / V01 USB bus states

Low-Speed Full-/High-Speed

State Bus-Driver D+ D- D+ D-

Idle-State Passive Low high differential 0 high Low differential 1

J-State Active Low high differential 0 high low differential 1

K-State Active High low differential 1 low high differential 0

SE0-State Active Low low NA low low NA

SOP (Start-of-Packet) Transition from the “Idle-State” into the “K-State” First bit of the SYNC-field

EOP (End-of-Packet) Data lines are set to low (SE0)

USB

10

MS_uC / fue1 / V01 USB bus states

Bus Reset SE0 is driven more than 2.5 ms

Suspend (Energy saving mode) USB devices fall asleep when the bus is inactive for 3 ms

After 3 ms high-speed devices switch into full-speed mode 100-875 ms after they go into suspend mode

Resume Resume sequences wake up the fallen asleep devices Data lines are driven into the K-State during 20 ms

USB

11

MS_uC / fue1 / V01 Data encoding

Data transmission begins with LSB (Least Significant Bit)

Data encoding is NRZI (Non-Return-To-Zero-Inverted)

USB

12

MS_uC / fue1 / V01

13

Bit Stuffing

Problem Synchronization loss when several high bits must be send

Solution Insertion of an additional low bit after the 6th high bit

USB

13

MS_uC / fue1 / V01 Transfer types (1/2)

Control transfer Configuration of the USB device Host sends requests to the device 10% of the bandwidth is reserved for control transfer

Interrupt Transfer Transfer of a few amount of data with guaranteed bandwidth

Mouse, keyboards etc. Host asks the interrupt endpoints periodically

Endpoint specifies the period 90% of the bandwidth is reserved for interrupt & isochronous

transfers Interrupt transfers are subject to the USB error detection

USB

14

MS_uC / fue1 / V01 Transfer types (2/2)

Bulk transfer (full- & high speed device) Transmission of large amount of data, which are not time

critical Printers, scanner & memory-Sticks

Transmission in the remaining available bandwidth

Isochronous transfer 90% of the bandwidth is reserved for interrupt & isochronous

transfers Data are sent every 1 ms frame Devices that require a constant data stream

Audio- und video capture devices

USB

15

MS_uC / fue1 / V01Protocol Layer (OSI Layer 2)

Data are transferred though USB data pipes Each pipe goes from the host and terminates in an endpoint

OUT1

C0 IN1 IN2 IN3 OUT1 OUT2 OUT3

Device 3

Address 12

C0 IN1 IN2 OUT1 OUT2

Device 1

Address 20

C0 IN1 OUT1

Device 2

Address 11

C0 IN1 OUT1 OUT2 OUT3 OUT4 OUT1

Root-Hub

Host

C0 IN1 OUT2 OUT3 OUT4 OUT5

HUB

Address 10

16

MS_uC / fue1 / V01 Pipes and endpoints

Sub address in a USB device with its own FIFO

USB

17

MS_uC / fue1 / V01

18

Type of endpoints

Each USB device has at least one control endpoint (endpoint 0) Configuration of the USB device

Each endpoint has a predefined FIFO size

All endpoint except endpoint 0 are unidirectional Each endpoint has a number (address)

IN- endpoints: Address 0x81 until 0x8F OUT- endpoints: Address 0x01 until 0x0F

Endpoint size in bytes

Bus-Driver Low-Speed Full-Speed High-Speed

Control-Transfer 8 8,16,32,64 64

Interrupt-Transfer 8 1 until 64 1 until 3072

Bulk-Transfer N/A 8,16,32,64 512

Isochronous-Transfer NA 1 until 1023 1 until 3072

18

MS_uC / fue1 / V01 Detection & treatment of errors

USB specifies various types of errors CRC check sum (Cyclic Redundancy Code)

CRC5: G(X) = X5 + X2 + 1 CRC16 : G(X) = X15 + X2 + 1

PID check 4 PID bits PID are transmitted twice

• Original and inverted forms

Bit stuff error Reception of more than six bits of same polarity in a row (logic

high)

Timeout error Confirmation of the received data outside a certain period

USB

19

MS_uC / fue1 / V01 Packet (1/2)

The USB data are transmitted by packets

Each packet starts with the following fields SYNC

Synchronization of the receiver PLL

PID (Packet-IDentifier) The upper 4 bits are the inverse of the lower 4 bits

USB

20

MS_uC / fue1 / V01 Packet (2/2)

Packets are classed in 4 groups Token-Packets

SOF Setup IN & OUT

Data-Packets Handshake-Packets Special-Packets

USB

21

MS_uC / fue1 / V01 SOF (token packet)

Host send a SOF packet (Start-Of-Frame) every milliseconds Prevent USB device from going into suspend mode

Low-Speed

Full-Speed 11-bit frame number is incremented systematically

EOP

EOP

SYNC PID Frame # CRC 5 EOP

0x01 0xA5 frame number 0xXX EOP

USB

22

MS_uC / fue1 / V01 Setup (token packet)

Host announces the sending of setup data to the devices

ADDR: 7 bits device address ENDP: 4 Bits endpoint number

SYNC PID ADDR ENDP CRC 5 EOP

0x01 0x2D Device address Endpoint number 0xXX EOP

USB

23

MS_uC / fue1 / V01 IN & OUT (token packet)

IN: Host requests the USB device to send data to it USB device then sends one packet DATAx

OUT: Host announces that it will send data to the USB device Host then sends one packet DATAx


0x01 0x69 Device address Endpoint number 0xXX EOP


0x01 0xE1 Device address Endpoint number 0xXX EOP

USB

24

MS_uC / fue1 / V01

25

DATA0 / DATA1 packets

The DATA0 & DATA1 packets are sent alternately

DATA0

DATA1

Number of data bytes 0..8 Bytes for Low Speed 0..1023 Bytes for Full Speed 0..1024 Bytes for High Speed

SYNC PID DATA CRC 16 EOP

0x01 0xC3 Data bytes 0xXXXX EOP


0x01 0x4B Data bytes 0xXXXX EOP

USB

25

MS_uC / fue1 / V01 Handshake packets ACK

Confirmation of the correct reception of a packet DATAx

NAK is only sent from the device OUT: Received data packet could not be processed IN: No data are available for sending

STALL is only sent from the device OUT: Received data packet could not be processed IN: No data are available for sending

SYNC PID EOP

0x01 0xD2 EOP

SYNC PID EOP

0x01 0x1E EOP

SYNC PID EOP

0x01 0x5A EOP

USB

26

MS_uC / fue1 / V01 Data transfer through USB

Host can only initiate a data transfer

Data transfer consists of 3 phases Phase 1 Host sends a token packet to the USB device Phase 2 Host or device sends the data Phase 3 Host or device acknowledges receipt

USB

27

MS_uC / fue1 / V01 Example of output data transfer (1/3)

Data transfer without error Address: 0x123 Endpoint: 1 Data: 0x00, 0x11, 0x22, 0x33


0x01 0xE1(OUT) 0x123 0x01 0xXX EOP


0x01 0xC3(DATA0) 0x00, 0x11, 0x22, 0x33 0xXXXX EOP

SYNC PID EOP

0x01 0xD2(ACK) EOP

OUT

OUT

IN

USB

28


FIFO of the USB device is full Address: 0x123 Endpoint: 1 Data: 0x00, 0x11, 0x22, 0x33





SYNC PID EOP

0x01 0x5A(NAK) EOP

OUT

OUT

IN

USB

29


USB device is disabled Address: 0x123 Endpoint: 1 Data: 0x00, 0x11, 0x22, 0x33





SYNC PID EOP

0x01 0x1E(STALL) EOP

OUT

OUT

IN

USB

30

MS_uC / fue1 / V01 Example of input data transfer (1/4)

Data transfer without error Address: 0x123 Endpoint: 2 Data: 0x00, 0x11, 0x22, 0x33


0x01 0x69(IN) 0x123 0x82 0xXX EOP



SYNC PID EOP

0x01 0xD2(ACK) EOP

OUT

IN

IN

USB

31


FIFO of the USB device is empty Address: 0x123 Endpoint: 2


0x01 0x69(IN) 0x123 0x82 0xXX EOP

SYNC PID EOP

0x01 0x5A(NAK) EOP

OUT

IN

USB

32


USB device is disabled Address: 0x123 Endpoint: 2


0x01 0x69(IN) 0x123 0x82 0xXX EOP

SYNC PID EOP

0x01 0x1E(STALL) EOP

OUT

IN

USB

33

MS_uC / fue1 / V01 Example of input data transfer (4/4)USB

34

MS_uC / fue1 / V01 Enumeration

Operating system must load the drivers for the USB devices Collect information about the device (descriptors) Assign a new address to the device

This process is called enumeration The enumeration proceeds as follows in Windows

Host tells Windows that a device has been connected Windows request from the device through address 0 its descriptor A new address is assigned to the device The device descriptor is requested again The configuration descriptor is requested The complete configuration descriptor (including interface and

endpoint descriptors) is requested Windows will search for the appropriate drivers and loads them Windows sets the device into the configured state

USB

35

MS_uC / fue1 / V01 USB Device Framework (OSI Layer 7)

Communication basis on driver & application level Collect information about the USB device (descriptors) Load the drivers for the USB device,

USB

36

MS_uC / fue1 / V01 USB Device Request

Host sends a “USB device request” to the USB device (endpoint0) Triggering the attribute exchanges (descriptors) of the USB

device

USB

37

MS_uC / fue1 / V01 Setup stage

Data transfer of the setup stage consists of the following 3 phases


0x01 0x2D (Setup) 0x00 0x00 0xXX EOP


0x01 0xC3(DATA0) USB Device Request 0xXXXX EOP

SYNC PID EOP

0x01 0xD2(ACK) EOP

OUT

OUT

IN

USB

38

MS_uC / fue1 / V01

Structure of the “USB Device Request“ (USB 2 Specification)

Offset Field Size(Bytes)

Description

0 bmRequestType 1 Characteristics of request: D7: Data transfer direction D6…5: Type D4…0: Recipient

1 bRequest 1 Specific request

2 wValue 2 Word-sized field that varies according to request

4 wIndex 2 Word-sized field that varies according to request; typically used to pass an index or Offset

6 wLength 2 Number of Bytes to transfer if there is a Data stage

USB

39

MS_uC / fue1 / V01 Specific requests

bRequest Description

CLEAR_FEATURE Delete or disable a feature

GET_CONFIGURATION Request the current configuration of the USB device

GET_DESCRIPTOR Request the descriptor specified in wValue

GET_INTERFACE Request the current interface settings of the USB device

GET_STATUS Request the current status of the USB device

SET_ADDRESS Change the address of the USB device

SET_CONFIGURATION Set the current configuration of the USB device

SET_DESCRIPTOR (Optional)

SET_FEATURE Enabled a feature in an interface or endpoint

SET_INTERFACE Sets the “alternative setting” for an interface

SYNCH_FRAME Used for synchronization (Isochronous Endpoints)

USB

40

MS_uC / fue1 / V01

Beispiel für USB Device Request19.04.23

41

MS_uC / fue1 / V01

42

SET_ADDRESS

SET_CONFIGURATION

GET_DESCRIPTOR

USB Example of USB device requests

42

MS_uC / fue1 / V01 USB device descriptors

Descriptors are data structures with a predefined format To exchange USB attributes between host and device

Type of descriptors Standard descriptors Class or vendor specific descriptors

Descriptors are asked with the request “GET_DESCRIPTOR” 1st byte of the descriptor contains its size 2nd byte of the descriptor informs about its type

USB

43

MS_uC / fue1 / V01 19.04.23

44

Standard descriptors (1/3)

Device Descriptor

Configuration Descriptor 1

Interface Descriptor 1

Endpoint Descriptor 1

Endpoint Descriptor n3

Interface Descriptor 2

Interface Descriptor n2

Endpoint Descriptor n3

Configuration Descriptor 2

Configuration Descriptor n1

String DescriptorID 1



iManufacturer

iProduct

iSerialNumber


(optional)

bNumConfigurations

bNumInterfaces

bNumEndpoints

iConfiguration


(optional)

iInterface

(optional)

MS_uC / fue1 / V01 Standard descriptors (2/3)

Describe the basic features and properties of the device

Device Descriptor USB-IF device class Supported standards (USB 1.1 or 2.0) Manufacturer Number of configurations

Configuration descriptor Size of the interface descriptors Size of the endpoint descriptors Power consumption of the various configurations

USB

45

MS_uC / fue1 / V01 Standard descriptors (3/3)

Interface Descriptor USB-IF device class Number of endpoints

Endpoint Descriptor Endpoint number (address) Transmission way (input or output) Transfer type

Bulk, interrupt or isochronous

String Descriptor Description of the USB device in text form

Class or vendor specific descriptors Specific to the USB-IF Device Classes

USB

46

MS_uC / fue1 / V01 Descriptor example (1/3)

Device DescriptorbLength 0x12 The Descriptor has a length of 18 bytesbDescriptorType 0x01 Device DescriptorbcdUSB 0x0200 USB Specification Number in BCD (2.00) bDeviceClass 0x00 Class is defined in the Interface-DescriptorbDeviceSubClass 0x00 Sub-Class is defined in the Interface-DescriptorbDeviceProtocol 0x00 Protocol is defined in the Interface-DescriptorbMaxPacketSize0 0x40 Size of Endpoint 0: 64 bytesidVendor 0x054C Vendor ID 0x054c (Sony Corporation)idProduct 0x0243 Product ID 0x0243bcdDevice 0x0100 Device release Number in BCD (1.00)iManufacturer 0x01iProduct 0x02iSerialNumber 0x03bNumConfigurations 0x01 1 configuration

USB

47

MS_uC / fue1 / V01 19.04.23

48

Descriptor example (2/3)

Configuration DescriptorbLength 0x09 The Descriptor has a length of 9 bytesbDescriptorType 0x02 Configuration DescriptorwTotalLength 0x0020 Total size of the Configuration-, Interface-, Endpoint-

DescriptorsbNumInterfaces 0x01 contains 1 interfacebConfigurationValue 0x01 this is configuration 1iConfiguration 0x00 no string descriptorbmAttributes 0x80 Bus PoweredbMaxPower 0x32 50 x 2 mA = 100 mA

Interface DescriptorbLength 0x09 The Descriptor has a length of 9 bytesbDescriptorType 0x04 Interface DescriptorbInterfaceNumber 0x00 this is interface 0 from configuration 1bAlternateSetting 0x00 no alternate settingbNumEndpoints 0x02 2 Endpoints (1 Bulk-IN, 1 Bulk-OUT)bInterfaceClass 0x08 Mass Storage Device ClassbInterfaceSubClass 0x06 SCSI transparent command setbInterfaceProtocol 0x50 Bulk-Only TransportiInterface 0x00 no string descriptor

MS_uC / fue1 / V01

49

Endpoint Descriptor 1bLength 0x07 The Desc. has a length of 7 bytesbDescriptorType 0x05 Endpoint DescriptorbEndpointAddress 0x81 Address 0x81, IN-EndpointTransfer Type 0x02 Bulk EndpointwMaxPacketSize 0x0200 FIFO-Size 512 BytesbInterval 0xFF not used for Bulk endpoints

Endpoint Descriptor 2bLength 0x07 The Desc. has a length of 7 bytesbDescriptorType 0x05 Endpoint DescriptorbEndpointAddress 0x02 Address 0x02, OUT-EndpointTransfer Type 0x02 Bulk EndpointwMaxPacketSize 0x0200 FIFO-Size 512 BytesbInterval 0xFF not used for Bulk endpoints

USB Descriptor example (3/3)

MS_uC / fue1 / V01USB-IF device classes

There are standard drivers for USB devices New USB devices can be developed without specific drivers

Mouse, keyboards ...

Standardization is achieved with the help of device classes bInterfaceClass bInterfaceSubClass bInterfaceProtocol

USB

50

MS_uC / fue1 / V01

Geräteklassen des USB Implementers ForumsClass (back) Base Class ID Descriptor Usage

Typical Devices

Audio Class 0x01 Interface Sound cards

Communication Device Class

0x02, 0x0A Interface USB to serial adapter,modem, …

Human Interface Device (HID)

0x03 Device, Interface Mouse, Keyboards, joystick …

Still Image Capture Device

0x06 Interface

Printer Class 0x07 Interface Printer

Mass Storage Device 0x08 Interface Memory stick, hard disk, floppy …

Hub 0x09 Device Hubs

Smart Card 0x0B Interface

Content Security 0x0D Interface

Video Class 0x0F Interface Video capture devices

Diagnostic Device 0xDC Device, Interface

Wireless Controller 0xE0 Interface Bluetooth, wireless USB

Miscellaneous 0xEF Device, Interface Palm, USB wireless

IrDA Bridge Device Class: 0xFESub class: 0x02

Interface IrDA devices

Test and measurements Class: 0xFESub class: 0x03

Interface Measure instruments

Vendor Specific 0xFF Device, Interface Some MP3 Player,CARME JTAG debugger

MS_uC / fue1 / V01 USB Keil library

USBD_Reset()

USBD_Suspend()

USBD_Resume()

USBD_P_SOF_Event()

USBD_EndPointx()

Enumeration

Reset Suspend

Resume

Out_Packet SOF

IN_Packet USBD_EndPointx()

USBD_Init()

OTG_FS_IRQHandler()

USB

52

ms_uc / fue1 / v01 1 usb programming microcontroller universal synchronous bus (usb) autumn 2012

Documents