modbus-frames

A simple modbus RTU library

By default this library knows about Coils (1/5/15), Discrete Inputs(2), Holding Registers(3/6/16), and Input Registers(4) only Users can extend this by replacing the encoder implementation

Decode

Takes in a slice of bytes, does basic validation (length/crc) then passes to the decoder Decoder returns an enum (e.g. ReadHoldingRegisters(address, func, num_regs, &[regs], crc)) which the application can then act upon Decoding doesn't require any copies to be made. Only references into the byte array

A basic command (for the sersor receiving commands) and response (for the central unit receiving responses) decoder are included. There is nothing particularly special about these decoders, a custom decoder can be written with very little fuss

Decoding Commands

use modbus_frames::decoder::command::CommonCommands;
let decoded = CommonCommands::try_from(command_frame).unwrap();
assert!(matches!(decoded, CommonCommands::ReadCoils(_)));

Decoding Responses

use modbus_frames::decoder::response::CommonResponses;
let decoded = CommonResponses::try_from(response_frame).unwrap();
assert!(matches!(decoded, CommonResponses::ReadCoils(_)));

Encode

Encoding is done using the builder pattern. The builder is initialised with the scratch array, which it then fills in as address, function, etc. are provided

use modbus_frames::{builder, Function};

let mut buff = [0u8; 20];
let frame = builder::build_frame(&mut buff)
                .for_address(1)
                .function(Function(2))
                .register(3)
                .finalise();
assert_eq!(frame.raw_bytes(), [1, 2, 0, 3, 224, 25]);
assert_eq!(frame.payload(), [0, 3]);