Struct Adu 

pub struct Adu { /* private fields */ }

A Modbus RTU frame: a unit address, a PDU, and a trailing CRC.

This is the complete unit of bytes an RTU transmitter puts on the bus and a receiver pulls off it. from_pdu builds one to send by appending the CRC; parse reads one received, verifying the CRC so a frame corrupted in transit never reaches the application. The frame lives in a fixed buffer, so neither path allocates.

Examples

use pamoja_modbus::Adu;

let frame = Adu::from_pdu(0x11, &[0x03, 0x00, 0x6B, 0x00, 0x03]).unwrap();
assert_eq!(frame.address(), 0x11);
assert_eq!(frame.function_code(), 0x03);

// A receiver validates the same bytes against the CRC they carry.
let received = Adu::parse(frame.as_bytes()).unwrap();
assert_eq!(received.pdu(), &[0x03, 0x00, 0x6B, 0x00, 0x03]);

Implementations

impl Adu

pub const MAX_LEN: usize = 256

The largest a Modbus RTU frame may be, in bytes.

pub fn from_pdu(address: u8, pdu: &[u8]) -> Result<Adu, ModbusError>

Builds a frame for a unit address and PDU, appending the CRC.

Arguments

• address - the unit (slave) address the frame is for.
• pdu - the protocol data unit: a function code followed by its data.

Returns

The frame ready to send.

Errors

Returns ModbusError::FrameTooLong if pdu is longer than a PDU may be, so the frame would exceed MAX_LEN bytes.

pub fn parse(bytes: &[u8]) -> Result<Adu, ModbusError>

Parses a received frame, verifying its CRC.

Arguments

• bytes - the raw frame as it came off the wire, CRC included.

Returns

The validated frame.

Errors

Returns ModbusError::FrameTooShort if bytes is shorter than a valid frame, ModbusError::FrameTooLong if it is longer than MAX_LEN, or ModbusError::CrcMismatch if the trailing CRC does not match the contents.

pub fn address(&self) -> u8

Returns the unit address, the first byte of the frame.

Returns

The unit (slave) address.

pub fn function_code(&self) -> u8

Returns the function code, the first byte of the PDU.

Returns

The function code. An exception response has its high bit set.

pub fn pdu(&self) -> &[u8]

Returns the PDU: the frame without its address and CRC.

Returns

The protocol data unit as a byte slice.

pub fn as_bytes(&self) -> &[u8]

Returns the whole frame, CRC included, ready for the wire.

Returns

The frame as a byte slice.

pub fn exception(&self) -> Option<Exception>

Returns the exception a device reported, if this frame is an exception response.

Returns

The Exception if the function code’s high bit is set and an exception byte follows it, otherwise None (including for a defined-but-unknown exception code).

pub fn response(&self) -> Response<'_>

Returns a reader over this frame’s PDU for decoding a response.

Returns

A Response borrowing the PDU.

Trait Implementations

impl Clone for Adu

fn clone(&self) -> Adu

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Adu

impl Debug for Adu

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Adu

impl PartialEq for Adu

fn eq(&self, other: &Adu) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for Adu