Blackmagic Studio Camera Manual Del Usuario página 158

Developer Information
158
Abstract Message Packet Format
Every message packet consists of a three byte header followed by an optional variable length data block.
The maximum packet size is 64 bytes.
Destination device (uint8)
Device addresses are represented as an 8 bit unsigned integer. Individual devices
are numbered 0 through 254 with the value 255 reserved to indicate a broadcast
message to all devices.
Command length (uint8)
The command length is an 8 bit unsigned integer which specifies the length of
the included command data. The length does NOT include the length of the
header or any trailing padding bytes.
Command id (uint8)
The command id is an 8 bit unsigned integer which indicates the message type
being sent. Receiving devices should ignore any commands that they do not
understand. Commands 0 through 127 are reserved for commands that apply to
multiple types of devices. Commands 128 through 255 are device specific.
Reserved (uint8)
This byte is reserved for alignment and expansion purposes. It should be set to zero.
Command data (uint8[])
The command data may contain between 0 and 60 bytes of data. The format of
the data section is defined by the command itself.
Padding (uint8[])
Messages must be padded up to a 32 bit boundary with 0x0 bytes. Any padding
bytes are NOT included in the command length.
Receiving devices should use the destination device address and/or the command identifier to determine
which messages to process. The receiver should use the command length to skip irrelevant or unknown
commands and should be careful to skip the implicit padding as well.