== Communication protocol between CAN and CC2540 chip  [[BR]]

[http://en.wikipedia.org/wiki/CAN_bus]

List of commands from CC2540 to CAN transiver: 
 1. Subscribe to a message
 2. Subscribe to a message with a bitmask
 3. Unsubscribe from messages
 4. Unsubscribe from messages with a bitmask
 5. List of all subscriptions 
 6. Reset filter state
 7. Passthrough message  

{{{
enum {
  CMD_SUBSCRIBE = 1,
  CMD_SUBSCRIBE_BITMASK,
  CMD_UNSUBSCRIBE,
  CMD_UNSUBSCRIBE_BITMASK,
  CMD_LIST,
  CMD_RESET,
  CMD_MSG
} cmd_type;

}}}


List of responces from CAN transiver: 

{{{
enum {
  ACK_SUBSCRIBE = 1,
  ACK_SUBSCRIBE_BITMASK,
  ACK_UNSUBSCRIBE,
  ACK_UNSUBSCRIBE_BITMASK,
  ACK_LIST,
  ACK_RESET,
  ACK_MSG
} cmd_type;

}}}


Command message structure

||= Byte =||= Bitmask =||= Description =||= Values =||
||     0        ||                      || Command code || 1 - 7||
||     1        ||                      || Payload size || 0 - 254||
||  2 - 255 ||                      || Payload ||||


Examples
 
{{{
   01:08:00:76:01:55:02:44:00:01
   04:02:00:76
   05:00
   06:00 
   07:76:06:05:01:02:03:04:05
}}}

 1. byte - subsribe command
 2. byte - payload size 8 byte = 2 CAN message IDs * 4 byte each 
 3. - 10. bytes 0076h & 0155h 


{{{
-------------------------------------------------
Standard CAN message example:  ID=76h
byte0 - 07h        (incoming CAN MESSAGE)               
byte1 - 00h    (00h=b00000000 bit.7=0 standard message)                 (this is byte.1 of std.ID excluding high 5 bits in this byte) 
    //if byte1 bit7=0 expect 1 more byte for ID

byte2 - 76h                                     			(this is byte.0 of std.ID) 
byte3 - DLC        (message data length code. also the payload.  8 in this example)
   byte4 - 01h	(byte.0 of data)
   byte5 - 02h	(byte.1 of data)
   byte6 - 03h	(byte.2 of data)
   byte7 - 04h	(byte.3 of data)
   byte8 - 05h	(byte.4 of data)
   byte9 - 06h	(byte.5 of data)
   byte10 - 07h	(byte.6 of data)
   byte11 - 08h	(byte.7 of data)

std.ID example 1 (ID=76h)
07h, 00h,76h, 01h,02h,03h,04h,05h,06h,07h

std.ID example 2 (ID=5DFh)
07h, 05h,DFh, 01h,02h,03h,04h,05h,06h,07h
-------------------------------------------------

-------------------------------------------------
Extended CAN message example:  ID=76h
byte0 - 07h        (incoming CAN MESSAGE)               
byte1 - 80h    (80h=b10000000 bit.7=1 extended message )               (this is byte.3 of ext.ID excluding  high 3 bits in this byte)
    //if byte1 bit7=1 expect 3 more bytes for ID
    byte2 - 00h                                     		       (this is byte.2 of ext.ID) 
    byte3 - 00h                                     		       (this is byte.1 of ext.ID) 
    byte4 - 76h                                     		       (this is byte.0 of ext.ID) 
byte5 - DLC        (message data length code. also the payload.  8 in this example)
   byte6 - 01h	(byte.0 of data)
   byte7 - 02h	(byte.1 of data)
   byte8 - 03h	(byte.2 of data)
   byte9 - 04h	(byte.3 of data)
   byte10 - 05h	(byte.4 of data)
   byte11 - 06h	(byte.5 of data)
   byte12 - 07h	(byte.6 of data)
   byte13 - 08h	(byte.7 of data)

ext.ID example 1 (ID=76h  ( b00000000000000000000000001110110 ))
07h, 80h,00h,00h,76h, 01h,02h,03h,04h,05h,06h,07h

ext.ID example 2 (ID=12345678h    ( b00010010001101000101011001111000 ))
07h, 92h,34h,56h,78h, 01h,02h,03h,04h,05h,06h,07h

ext.ID example 3 (ID=1FFFFFFFh    ( b00011111111111111111111111111111  29 bits, max value of ext.ID))
07h, 9Fh,FFh,FFh,FFh, 01h,02h,03h,04h,05h,06h,07h
--------------------------------------------------
}}}