USB - Universal Serial Bus
MS_uC / fue1 / V10
11- 1
Programming Microcontrollers
USB – Universal Serial Bus
Autumn term 2009
ARM966
CORE
E
w/DSP
96 MHz
DMA
PFQ
BC
64K or 96K
Byte SRAM
256K or 512K
Byte Burst Flash
Enter
MAC
USB
2.0FS
CAN
2.0B
INTR CLK
32K Byte
GPIO
Cantl Cantl
Burst Flash
e
e
LVD PLL JTAG ETM9 OTP EXT.
Memo Bus
BOD
ADC
RTC
TIM
SPI
STR912FAW44
I2C
UART
USB - Universal Serial Bus
MS_uC / fue1 / V10
History
11- 2
 The USB Implements Forum (USB IF) has been founded in 1995
 The first standard (USB 1.0) has been specified a year later
 USB was planned to connect different peripheral devices to a universal
interface
 Mouse, keyboard, printer etc.
 The USB 2.0 standard follows in 2000
 Speed has been enhanced to 480 MBit/s
This enables to connect also hard discs, video cameras etc.
USB - Universal Serial Bus
MS_uC / fue1 / V10
Generality
11- 3
 USB is a asymmetrical bus
 We distinguish between Host (PC) and Device (also called function)
 The type of transmission is asynchronous serial bit
 The transmitted speed are
 1.5MBit/s (Low-Speed)
 12MBit/s (Full-Speed)
 480MBit/s (High-Speed, only for USB 2.0)
 Since USB 2.0, it is also possible to connect the devices between them
 OTG (On-The-Go)
USB Topology
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11- 4
 127 devices can be connected to the USB bus (incl. Hubs)
 Each device receive a unique address from the Host (PC)
Host
Root-Hub
1
2
Hub
3
Device 1
4
Device 2
Hub
5
Device 3
6
Device 4
USB - Universal Serial Bus
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USB Power supply
11- 5
 Bus-Powered Hubs
 Supply voltage is furnished by the host/hub
 The total power consumption of the connected devices must be < 500 mA
 Self-Powered-Hubs
 Supply voltage is furnished separately
 Each device can consume 500 mA
USB - Universal Serial Bus
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Electrical Interface
11- 6
 The USB cable contains 4 lines
 VCC (+5V)
 GND
 D+ and D- (0 and 3.3 V), which work in a differential mode
Difference bigger than +200 mV represents a logic 1
Difference smaller than -200 mV represents a logic 0
USB connectors
USB - Universal Serial Bus
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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
connected
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11- 8
Connection & speed investigation
 The Host/Hub must recognize the devices that are connected to its outputs
 The Host/Hub begins therefore with the speed investigation
 Pull up or pull down resistors
Full-Speed and High speed Device
Low-Speed Device
Bus states (1)
USB - Universal Serial Bus
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11- 9
Low-Speed
State
BusDriver
D+
D-
Idle-State
passive
Low
high
J-State
Active
Low
K-State
Active
SE0-State
Active
(Single End Zero)
Full-/High-Speed
D+
D-
differential 0
high
Low
differential 1
high
differential 0
high
low
differential 1
High
low
differential 1
low
high
differential 0
Low
low
NA
low
low
NA
 SOP (Start-of-Packet)
 The transition from the “idle” in to the “K” state
 This change is the first bit of the SYNC field
 EOP (End-of-Packet)
 The “SE0” state is kept during 2 cycles followed by the “Idle” state
USB - Universal Serial Bus
MS_uC / fue1 / V10
Bus states (2)
11- 10
 Bus Reset
 SE0 is activated during 2.5 ms
 Suspend
 A USB device must enter in to a sleep mode to save energy
If there is no activity on the USB bus during 3 ms
 The High-Speed devices go in to the Full-Speed modes after 3 ms
After 100 to 875 µs they go in to the suspend state
 Resume
 A suspended device must be wake up with a resume sequence
Data lines must be set in to the “K” state during 20 ms followed by a SOF
sequence
USB - Universal Serial Bus
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11- 11
State Diagram
USB - Universal Serial Bus
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Data coding
11- 12
 The transmission begins with the LSB (Least Significant Bit)
 The transmitted bits are coded in to NRZI
 Non-Return-To-Zero-Inverted
USB - Universal Serial Bus
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USB protocol
11- 13
 The USB is a polled bus (nobody speaks if not asked. No interrupts)
 The Host controller initiates all data transfers
 Transaction type and direction
 USB address
 Endpoint (token package)
USB - Universal Serial Bus
MS_uC / fue1 / V10
11- 14
USB Communication flow
USB - Universal Serial Bus
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Transfer type (1)
11- 15
 Control Transfer
 The Control transfer enables to configure the Device
 The Host sends the requests to the Device
 10% of the band width is used for this kind of transfer
 Interrupt Transfer
 Transfer of a few amount of data, which must be send periodically
Mouse, keyboards etc.
 The Host polls the Endpoints
Period is defined in the Endpoint
 90% of the Bandwidth is reserved for Interrupt and Isochronous Transfers
USB - Universal Serial Bus
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Transfer type (2)
11- 16
 Bulk Transfer
 Transfer of great amounts of data, which is not time critical
Printers, scanner and memory sticks
 Transfer are realized with the remaining Bandwidth
 Isochronous Transfer
 90% of the Bandwidth is reserved for Interrupt and Isochronous Transfers
 The data are transferred one time per frame of 1 ms
USB - Universal Serial Bus
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Data Package
11- 17
 The data are transmitted within packages
 Token-Packets
SOP
Setup
IN & OUT
 Data-Packets
 Handshake-Packets
 Special-Packets
USB - Universal Serial Bus
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Structure of the packages
11- 18
 SYNC
 Each package begins with the SYNC field
 Synchronization of the Device PLL with the Host one
 PID
 The second field is the PID (Packet-Identifier) one
 The 4 first bits are the complement of the 4 last ones
 The next fields depend on the package types
 The CRC (Cyclic Redundancy Check) is often the next-to-last field
 The EOP is the last field
SOF (Token-Packet)
USB - Universal Serial Bus
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11- 19
 Host / Hub sends a SOF every ms (Start-of-Frame)
 To avoid that the Device enter into the Suspend mode
 Low-Speed
EOP
EOP
 Full-Speed
 Frame # : 11-Bit frame number, which is systematically incremented
SYNC
PID
Frame #
CRC 5
EOP
0x01
0xA5
frame number
0xXX
EOP
USB - Universal Serial Bus
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Setup (Token-Packet)
11- 20
 The Host announces the sending of setup data with this Package
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0x2D
Device address
Endpoint number
0xXX
EOP
 ADDR: 7-Bit Device-Address
 ENDP: 4-Bit Endpoint Number
USB - Universal Serial Bus
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IN & OUT (Token-Packet)
11- 21
 IN: Le Host ask the Device to send him Data
 The Device will then send a Data to the Host.
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0x69
Device address
Endpoint number
0xXX
EOP
 OUT: The Host tells to the Device, that he will send Data to him
 The Host will then send a Data to the Device
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0xE1
Device address
Endpoint number
0xXX
EOP
USB - Universal Serial Bus
MS_uC / fue1 / V10
DATA0 / DATA1 (Data-Packet)
11- 22
 The package DATA0 and DATA1 contain the data to transmit
 DATA0 and DATA1 are send alternatively for synchronization purposes
 0..8 Bytes for Low Speed
 0..1023 Bytes for Full Speed
 0..1024 Bytes for High Speed
 DATA0
SYNC
PID
DATA
CRC 16
EOP
0x01
0xC3
Data bytes
0xXXXX
EOP
SYNC
PID
DATA
CRC 16
EOP
0x01
0x4B
Data bytes
0xXXXX
EOP
 DATA1
USB - Universal Serial Bus
MS_uC / fue1 / V10
Handshake-Packets
11- 23
 ACK
 Confirmation that the package Data has been received without errors
SYNC
PID
EOP
0x01
0xD2
EOP
 NAK is only send by the device
 The package Data could not be treated (OUT)
 There are no data to send (IN)
SYNC
PID
EOP
0x01
0x5A
EOP
 STALL is only send by the device
 The device is not activated
SYNC
PID
EOP
0x01
0x1E
EOP
USB - Universal Serial Bus
MS_uC / fue1 / V10
Data transmission
11- 24
 The Data transmission is realized during 3 phases
 The host sends a token package to the device (phase 1)
 Either the host or the device sends the data (phase 2)
 The successful reception is confirmed either by the Host or by the Device
with a handshake (phase 3)
Output transmission example (1)
USB - Universal Serial Bus
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11- 25
 Transmission without errors
 Address: 0x123
 Endpoint: 1
 Data: 0x00, 0x11, 0x22, 0x33
OUT
OUT
IN
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0xE1(OUT)
0x123
0x01
0xXX
EOP
SYNC
PID
DATA
CRC 16
EOP
0x01
0xC3(DATA0)
0x00, 0x11, 0x22, 0x33 0xXXXX
EOP
SYNC
PID
EOP
0x01
0xD2(ACK)
EOP
USB - Universal Serial Bus
MS_uC / fue1 / V10
Output transmission example (2)
11- 26
 The FIFO is full
 Address: 0x123
 Endpoint: 1
 Data: 0x00, 0x11, 0x22, 0x33
OUT
OUT
IN
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0xE1(OUT)
0x123
0x01
0xXX
EOP
SYNC
PID
DATA
CRC 16
EOP
0x01
0xC3(DATA0)
0x00, 0x11, 0x22, 0x33
0xXXXX
EOP
SYNC
PID
EOP
0x01
0x5A(NAK)
EOP
USB - Universal Serial Bus
MS_uC / fue1 / V10
Output transmission example (3)
11- 27
 The USB device is not activated
 Address: 0x123
 Endpoint: 1
 Data: 0x00, 0x11, 0x22, 0x33, 0x44, 0x55
OUT
OUT
IN
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0xE1(OUT)
0x123
0x01
0xXX
EOP
SYNC
PID
DATA
CRC 16
EOP
0x01
0xC3(DATA0)
0x00, 0x11, 0x22, 0x33
0xXXXX
EOP
SYNC
PID
EOP
0x01
0x1E(STALL)
EOP
Input transmission example (1)
USB - Universal Serial Bus
MS_uC / fue1 / V10
11- 28
 Transmission without errors
 Address: 0x123
 Endpoint: 2
 Data: 0x00, 0x11, 0x22, 0x33
OUT
IN
IN
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0x69(IN)
0x123
0x02
0xXX
EOP
SYNC
PID
DATA
CRC 16
EOP
0x01
0xC3(DATA0)
0x00, 0x11, 0x22, 0x33 0xXXXX
EOP
SYNC
PID
EOP
0x01
0xD2(ACK)
EOP
Input transmission example (2)
USB - Universal Serial Bus
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11- 29
 The FIFO is full
 Address: 0x123
 Endpoint: 2
OUT
IN
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0x69(IN)
0x123
0x02
0xXX
EOP
SYNC
PID
EOP
0x01
0x5A(NAK)
EOP
Input transmission example (3)
USB - Universal Serial Bus
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11- 30
 The USB device is not activated
 Address: 0x123
 Endpoint: 2
OUT
IN
SYNC
PID
ADDR
ENDP
CRC 5
EOP
0x01
0x69(IN)
0x123
0x02
0xXX
EOP
SYNC
PID
EOP
0x01
0x1E(STALL)
EOP
USB - Universal Serial Bus
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USB Device Framework
(OSI Layer 7)
 USB Device Framework define how to communicate at the driver layer
 A firmware programmer will be interested basically at this layer
USB - Universal Serial Bus
MS_uC / fue1 / V10
USB Device Request
11- 32
 The Host sends a “USB Device Request” to the Devices to start an action
 Endpoint 0
 Structure of a Request
Offset
Field
Size
(Bytes)
Description
0
bmRequestType
1
Characteristics of request
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 - Universal Serial Bus
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Standard Device Requests
11- 33
bRequest
Description
CLEAR_FEATURE
Clear or activate a features
GET_CONFIGURATION
Ask the Device to send its actual configuration number
GET_DESCRIPTOR
Ask the Device to send its descriptor, which has been
specified with wValue
GET_INTERFACE
Ask the Device to send its actual “alternate setting“
GET_STATUS
Ask the Device to send its actual state
SET_ADDRESS
Change the Device address
SET_CONFIGURATION
Set the Device in to a new configuration
SET_DESCRIPTOR
(Optional)
SET_FEATURE
Activate a new Feature in a Interface or an Endpoint
SET_INTERFACE
Set the “alternate setting“ for the Interface
SYNCH_FRAME
Can be used to synchronize the Isochronous Endpoints
USB - Universal Serial Bus
MS_uC / fue1 / V10
Descriptors
11- 34
 Descriptors are predefined structures, which enable to exchange
attributes between the host and the device
 Type of descriptors
 Standard descriptors
 Specific descriptors
Class or Vendor
 The descriptors are asked from the Host through the Standard Device
Request “GET_DESCRIPTOR”
 The first Byte contains the size of the descriptor
 The second the type of the descriptor
 The standard descriptors describes the standard function and the
properties of the USB Device
Hierarchy of the Standard
descriptors
USB - Universal Serial Bus
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String Descriptor
ID 1
11- 35
iManufacturer
String Descriptor
ID 2
iProduct
String Descriptor
ID 3
iSerialNumber
String Descriptor
ID 4
(optional)
Device
Descriptor
bNumConfigurations
Configuration
Descriptor 1
iConfiguration
(optional)
Configuration
Descriptor 2
Configuration
Descriptor n1
bNumInterfaces
String Descriptor
ID 5
iInterface
(optional)
Interface
Descriptor 1
Interface
Descriptor 2
Interface
Descriptor n2
bNumEndpoints
Endpoint
Descriptor 1
Endpoint
Descriptor n3
Endpoint
Descriptor n3
USB - Universal Serial Bus
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Type of standard descriptors (1)
11- 36
 Device Descriptor
 Class of the Device
 The supported standard (USB 1.1 or 2.0)
 The manufacture
 A list of the Device Configurations
 Configuration Descriptor
 Class of the Device
 A list of the Configuration Interfaces
 A list of the Endpoints
 Interface Descriptor
 Class of the Device
 A list of the Endpoints
USB - Universal Serial Bus
MS_uC / fue1 / V10
Type of standard descriptors (2)
11- 37
 Endpoint Descriptor
 Endpoint properties
 Endpoint number
 Endpoint direction (IN or OUT)
 Transfer type
Bulk, Interrupt or Isochronous
 String Descriptor
 Text description of the Device
 Class of Vendor-Specific Descriptors
 Descriptor that are specific to the Device classes
USB - Universal Serial Bus
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Enumeration
11- 38
 The OS must install the drivers for the new connected Device
 This task is called Enumeration and it is executed in Windows as follow
 Host tells Windows that a new Device has been connected
 Windows calls the Device descriptor of the Device with the temporary
address 0
 A new address is attributed to the Device
 The Device descriptor is called for a second time
 The Configuration descriptor is called without the Interface & Endpoint
descriptors
 The complete Configuration descriptor is called
 Windows search the corresponding drivers and install them
 Window configure the Device
USB - Universal Serial Bus
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Example for an application (1)
11- 39
Device Descriptor
bLength
bDescriptorType
bcdUSB
bDeviceClass
bDeviceSubClass
bDeviceProtocol
bMaxPacketSize0
idVendor
idProduct
bcdDevice
iManufacturer
iProduct
iSerialNumber
bNumConfigurations
0x12
0x01
0x0200
0x00
0x00
0x00
0x40
0x054C
0x0243
0x0100
0x01
0x02
0x03
0x01
The Descriptor has a length of 18 bytes
Device Descriptor
USB Specification Number in BCD (2.00)
Class is defined in the Interface-Descriptor
Sub-Class is defined in the Interface-Descriptor
Protocol is defined in the Interface-Descriptor
Size of Endpoint 0: 64 bytes
Vendor ID 0x054c (Sony Corporation)
Product ID 0x0243
Device release Number in BCD (1.00)
1 configuration
USB - Universal Serial Bus
MS_uC / fue1 / V10
Example for an application (2)
11- 40
Configuration Descriptor
bLength
bDescriptorType
wTotalLength
0x09
The Descriptor has a length of 9 bytes
0x02
Configuration Descriptor
0x0020 Total size of the Configuration-, Interface-, EndpointDescriptors
bNumInterfaces
0x01
contains 1 interface
bConfigurationValue 0x01
this is configuration 1
iConfiguration
0x00
no string descriptor
bmAttributes
0x80
Bus Powered
bMaxPower
0x32
50 x 2 mA = 100 mA
Interface Descriptor
bLength
0x09
bDescriptorType
0x04
bInterfaceNumber 0x00
bAlternateSetting 0x00
bNumEndpoints
0x02
bInterfaceClass
0x08
bInterfaceSubClass 0x06
bInterfaceProtocol 0x50
iInterface
0x00
The Descriptor has a length of 9 bytes
Interface Descriptor
this is interface 0 from configuration 1
no alternate setting
2 Endpoints (1 Bulk-IN, 1 Bulk-OUT)
Mass Storage Device Class
SCSI transparent command set
Bulk-Only Transport
no string descriptor
USB - Universal Serial Bus
MS_uC / fue1 / V10
Example for an application (3)
11- 41
Endpoint Descriptor 1
bLength
bDescriptorType
bEndpointAddress
Transfer Type
wMaxPacketSize
bInterval
0x07
0x05
0x81
0x02
0x0200
0xFF
The Desc. has a length of 7 bytes
Endpoint Descriptor
Address 0x81, IN-Endpoint
Bulk Endpoint
FIFO-Size 512 Bytes
not used for Bulk endpoints
Endpoint Descriptor 2
bLength
bDescriptorType
bEndpointAddress
Transfer Type
wMaxPacketSize
bInterval
0x07
0x05
0x02
0x02
0x0200
0xFF
The Desc. has a length of 7 bytes
Endpoint Descriptor
Address 0x02, OUT-Endpoint
Bulk Endpoint
FIFO-Size 512 Bytes
not used for Bulk endpoints