Free-D Protocol Rust Implementation

This aims to provide a library of all the types used by the FreeD protocol, in rich Rust semantics, for interacting with free-d hardware or simulating it for your own implementations.

I found that there were very few public implementations of the Free-D protocol available, and none that implemented the entire protocol.

Current Payload implementations, as per the spec:

• PollPayload
• PositionPollPayload
• SystemStatusPayload
• SystemControlPayload
• TargetDataPayload
• ImageDataPayload
• EEPROMDataPayload
• EEPROMDataRequestPayload
• CameraCalibrationPayload
• DiagnosticModePayload

These are designed to be wrapped in a Message<T: Serialise + Deserialise> struct, which appends the command tag and camera information, alongside a checksum before serialisation. Likewise deserialised data is returned as a Message<T>, which the payload may be extracted from.

There is also a simple Serialise and Deserialise trait interface implemented for all payloads, so that data may be sent over UDP or serial interfaces.

//Example sending data.

//set up a position packet for a camera
let payload: PositionPollPayload = PositionPollPayload {
    pitch: i24::new(-1000),
    yaw: i24::new(0),
    roll: i24::new(0),
    pos_z: i24::new(150500),
    pos_y: i24::new(0),
    pos_x: i24::new(0),
    zoom: u24::new(100),
    focus: u24::new(4096),
    userdefined: 0,
}

//wrap the payload in a Message struct, which automatically appends the command type & checksum
let message: Message<PositionPollPayload> = Message::new(payload, ALL_CAMERAS);

//serialise to an array
let serial: Vec<u8> = message.serialise();

//send the data!
Send(serial, port, address);

Deserialising data to Payload types is a little more complicated, requiring a match on the command byte in the incoming message. I am open to suggestions or PRs that will improve these ergonomics.

let command: Commands = get_command_type(messagebuffer);

if command == Commands::POSITION_POLL 
{
    let payload: Message<PositionPollPayload> = deserialise(messagebuffer);

    //do stuff with the position payload
}
else if command == Commands::SYSTEM_STATUS
{
    let payload: Message<SystemStatusPayload> = deserialise(messagebuffer);
    //do stuff with the system status payload
}