5.7 KiB
CanBoot Protocol
Frame
Each command and response is framed as follows:
<2 byte header> <1 byte command> <1 byte payload word length> <payload> <2 byte trailer> <2 byte crc>
- The header is <0x01><0x88>
- The trailer is <0x99><0x03>
- The payload length must be specified in 4 byte words. A value of 1 corresponds to a payload 4 bytes in length.
- The payload is optional depending on the command. If present it must be a multiple of 4 bytes in length.
- Any arguments within the payload should be sent in big endian byte order.
- The CRC is performed on the entire frame (header through trailer) using the standard CRC16-CCITT algorithm.
- The CRC and all integer arguments are sent in big endian byte order.
Commands
The bootloader accepts the following commands:
Connect: 0x11
Initiates communication with the bootloader. This command has no payload:
<0x01><0x88><0x11><0x00><0x99><0x03><CRC>
Responds with acknowledged containing a 4 byte payload in the following format:
<0x11><0x00><2 byte block_size>
The block_size is a 16 bit unsigned integer in big endian byte order. It
represents the size of a block (in bytes) expected in the send block and
request block commands. Typically this should be 64 bytes.
Send Block: 0x12
Sends a block of data to be written. This command takes a block index
argument followed by the block of data:
<0x01><0x88><0x12><1 byte payload word length><4 byte block_index><block_data><0x99><0x03><CRC>
The payload word length will include one word for the block index argument
plus block_size // 4 for the data.
The block_index refers to a single block within the binary of block_size
bytes, starting at 0. It should be sent as 32-bit integer in big endian format.
The block_data is the data contained with in the block. If the final block
is less than block_size in length it should be padded with 0xFF to fill
the remainder.
Responds with acknowledged containing a 4 byte payload in the following format:
<0x12><0x00><2 byte block_index>
The returned block_index is a 16-bit unsigned integer in big endian byte
order. It must match the block_index sent in the request.
EOF: 0x13
Indicates that the end of file has been reached and the bootloader should write any remaining in the buffer to flash. This command has no payload:
<0x01><0x88><0x13><0x00><0x99><0x03><CRC>
Responds with acknowledged containing a 4 byte payload in the following format:
<0x13><0x00><2 byte page_count>
The page_count is a 16-bit unsigned integer in big endian byte order. It
represents the total number of pages written to flash.
Request Block: 0x14
Requests of block of data in flash, used for verification. This command takes
a block index argument indicating the block to read:
<0x01><0x88><0x14><0x01><4 byte block_index><0x99><0x03><CRC>
The block_index is a 32-bit unsigned integer in big endian byte order.
Responds with acknowledged containing a payload in the following format:
<0x14><0x00><2 byte block_index><block_data>
The returned block_index is a 16-bit unsigned integer in big endian byte
order. It must match the block_index sent in the request.
Complete: 0x15
Indicates that process is complete. The bootloader will reset and attempt to jump to the application after responding to this command:
<0x01><0x88><0x15><0x00><0x99><0x03><CRC>
Responds with acknowledged containing a 4 byte payload in the following format:
<0x15><0x00><0x00><0x00>
Responses
All responses contain a payload of at least 4 bytes, where the first byte contains the command being responded to. It is possible for a response to include another argument within this first word.
Acknowledged: 0xa0
This response indicate successful execution of a command:
<0x01><0x88><0xa0><payload word length><payload><0x99><0x03><CRC>
The payload depends on the command.
Invalid Command: 0xf0
Indicates the the bootloader received an invalid command:
<0x01><0x88><0xf0><0x01><4 byte payload><0x99><0x03><CRC>
The payload is in the following format:
<1 byte orig_command><0x00><0x00><0x00>
The orig_command is the invalid command received.
CRC Mismatch: 0xf1
Indicates that CRC verification failed on the requested command:
<0x01><0x88><0xf1><0x01><4 byte payload><0x99><0x03><CRC>
The payload is in the following format:
<1 byte orig_command><0x00><2 byte calculated_crc>
The command is the command received from the original request.
The calculated_crc is a 16-bit unsigned integer represented
the CRC calculated on the frame.
Invalid Block: 0xf2
Indicates that the payload contained in a send block command is not of the expected lenght:
<0x01><0x88><0xf2><0x01><4 byte payload><0x99><0x03><CRC>
The payload is in the following format:
<1 byte orig_command><0x00><0x00><0x00>
The orig_command is the command received which generated
Invalid Trailer: 0xf3
Indicates that the trailer of the frame is not <0x88><0x03>:
<0x01><0x88><0xf3><0x01><4 byte payload><0x99><0x03><CRC>
The payload is in the following format:
<1 byte orig_command><0x00><0x00><0x00>
The orig_command is the command received from the original request.
Invalid Length: 0xf4
Indicates that the payload length of a request is too large to fit within the buffer:
<0x01><0x88><0xf4><0x01><4 byte payload><0x99><0x03><CRC>
The payload is in the following format:
<1 byte orig_command><0x00><0x00><0x00>
The orig_command is the command received from the original request.