Benutzer:Siro/i2cprotokoll

I2C Protokoll

Version 0.3

DEFINITIONS

layer0	Hardwareebene (i2c)
layer1	Packetebene
endpoint	externe Hardware/Software (nicht näher definiert)

Vorderungen

Alle Devices sollen die max. Busgeschwindigkeit verwenden

Alle Daten werden in Paketen übertragen

Alle Daten werden vom Master "gepollt"

Alle Devices können bis zu 254 Endpoints haben (Endpoint 0 reserved)

Jeder Endpoint hat mind. 8 byte in-Buffer & mind. 8 byte out-Buffer

Jeder Endpoint hat einen Status-Byte das Informationen über die Buffer bereitstellt

Device Overview

Device
	|----	Endpoint 0
	|----	Endpoint 1
	...
	|----	Endpoint n
		|---in_buffer
		|---out_buffer

Packet

Header	Data
1 Byte	1-8 Byte

Header:

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3 - 0
reserved	READ/!WRITE	Command/!Data	Parity	Packetsize

Note: Parity can be EVEN, ODD, XOR, NONE, Parity does include packetsize-Bits and all DATA
Note: Command/!DATA marks this packet as COMMAND packet or as DATA packet
Note: READ/!WRITE is the direction of data transfers

COMMAND PACKET

Header	Byte 1	Byte 2	Byte 3	Byte 4	Byte 5	Byte 6	Byte 7	Byte 8
XX1XXXXX	COMMAND	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)

handled by layer1

DATA PACKET

Header	Byte 1	Byte 2	Byte 3	Byte 4	Byte 5	Byte 6	Byte 7	Byte 8
XX0XXXXX	DATA	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)

handled by userprogram

COMMANDS

all "get" commands load data into the out_buffer & change status to ready for read
all "set" commands store data into the in_buffer & change status to !ready for write
Note:

if in_buffer is full/not ready to write the data is dropped

if out_buffer is not ready for read, 0 is returned
querry status first !

0x00
invalid (reserved)

0x01    PING
copies complement of inputbuffer to outputbuffer
to run bus-speed-test

0x02    GET DEVICE DESCRIPTOR
returns information about the device
max supported protocol version
endpoint count
...

0x03    GET DEVICE STATUS
return device status, for example:
ready for read
ready for write
...

0x04    GET ENDPOINT DESCRIPTOR
2.byte: endpoint
returns information about the endpoint
must be less then max. device endpoints

0x05    SET ENDPOINT
2.byte: endpoint
must be less then max. device endpoints

0x06    GET CURRENT ENDPOINT
return active endpoint (default: 0)

0x07    GET CENDPOINT STATUS
return current endpoint status, for example:
ready for read
ready for write
...

0x08    CONFIGURE ENDPOINT
manage power, enable/disable endpoint
...

0x09    GET AENDPOINT STATUS
return any endpoint status
2.byte: endpoint
for example:
ready for read
ready for write
...

DATA PACKET

Data packets are stored in the in_buffer of the current endpoint if READ/!WRITE is 0 & buffer is ready. The users programm is notified that theres new data.

Data packets are read from the out_buffer of the current endpoint if READ/!WRITE is 1 & buffer is ready. Packet-length field should be ignored. The users programm is notified that the host request new data.

Device Response

Header is ==0    NO VALID DATA
the buffer you read from was not ready
Header is > 0    DATA
VALID:
data-packet length should be greater than 0
packet parity does match
INVALID:
data-packet length is 0
packet parity doesn't match