Benutzer:Siro/i2cprotokoll

I2C Protokoll

Version 0.4

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 müssen einen Endpoint 0 haben (das Device selber)

Alle Devices können bis zu 254 Endpoints haben

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
		|---status_byte
		|---in_buffer
		|---out_buffer

Packet

Overview
Packet:

Header	Data
1 Byte	1-8 Byte

Header:

Bit 7	Bit 6	Bit 5 - 0
Command&!Data	Parity	see below

Note: Parity can be EVEN, ODD, XOR, NONE, Parity does include packetsize-Bits and all DATA
Note: Command&!DATA marks this packet as either COMMAND packet or as DATA packet

COMMAND PACKET
Header:

Bit 7	Bit 6	Bit 5	Bit 4 - 1	Bit 0
1	Parity	0 (reserved)	COMMAND	Data packet count (0 or 1)

Packet:

Header	Byte 1
1X0XXXXX	DATA (only if <header:0> is set)

handled by layer1

DATA PACKET
Header:

Bit 7	Bit 6	Bit 5	Bit 4	Bit 3 - 0
0	Parity	0 (reserved)	READ&!WRITE	Packetsize

Packet:

Header	Byte 1	Byte 2	Byte 3	Byte 4	Byte 5	Byte 6	Byte 7	Byte 8
0X0XXXXX	DATA	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)	DATA (optional)

Note: READ&!WRITE is the direction of data transfers
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 ENDPOINT DESCRIPTOR
2.byte: endpoint
returns information about the endpoint
can be display, soundd. ,networkd. ,inputd. ...
must be less then max. device endpoints

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

0x03    SET CURRENT ENDPOINT
2.byte: endpoint
must be less then max. device endpoints

0x04    GET CURRENT ENDPOINT
return active endpoint (default: 0)

0x05    GET CENDPOINT STATUS
return current endpoint status, for example:
ready for read
ready for write
packet was dropped
packet was invalid
...

0x06    CONFIGURE ENDPOINT
manage power, enable/disable endpoint
...

0x07    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