Only the first command packet in a session has subtype 0x53. Maximum length of data field in a packet is 2048 bytes, which yields in 2054 total packet length. Checksum is a simple 16 bit arithmetic sum of all bytes in the data field. As already mentioned above, length and checksum values are transmitted least significant byte first. If the camera does not respond to a command in reasonable time, or responds with a NAK, the command can be resent.
Command is a sequence of bytes sent in the data field of a command packet.
3 vdata Set value of vdata register 4 none Read value of vdata register Commands 0 and 3 are replied with a single ACK 0x06. Commands 1 and 4 are replied with a sequence of data packets, each of them must be ACK'ed by the host. Command 2 typically is issued with a single zero byte as an argument. Command 3 is issued with an argument of variable number of bytes. If this is a printable string, it should not include the trailing zero byte.