Trait libmodbus_rs::ModbusRTU [−] [src]

pub trait ModbusRTU {
    fn new_rtu(
        device: &str, 
        baud: i32, 
        parity: char, 
        data_bit: i32, 
        stop_bit: i32
    ) -> Result<Modbus, Error>;

    fn rtu_get_serial_mode(&self) -> Result<SerialMode, Error>;

    fn rtu_set_serial_mode(&mut self, mode: SerialMode) -> Result<(), Error>;

    fn rtu_get_rts(&self) -> Result<RequestToSendMode, Error>;

    fn rtu_set_rts(&mut self, mode: RequestToSendMode) -> Result<(), Error>;

    fn rtu_set_custom_rts(
        &mut self, 
        _mode: RequestToSendMode
    ) -> Result<i32, Error>;

    fn rtu_get_rts_delay(&self) -> Result<i32, Error>;

    fn rtu_set_rts_delay(&mut self, us: i32) -> Result<(), Error>;
}

The RTU backend (Remote Terminal Unit) is used in serial communication and makes use of a compact, binary representation of the data for protocol communication. The RTU format follows the commands/data with a cyclic redundancy check checksum as an error check mechanism to ensure the reliability of data. Modbus RTU is the most common implementation available for Modbus. A Modbus RTU message must be transmitted continuously without inter-character hesitations (extract from Wikipedia, Modbus, http://en.wikipedia.org/wiki/Modbus (as of Mar. 13, 2011, 20:51 GMT).

The Modbus RTU framing calls a slave, a device/service which handle Modbus requests, and a master, a client which send requests. The communication is always initiated by the master.

Many Modbus devices can be connected together on the same physical link so before sending a message, you must set the slave (receiver) with modbus_set_slave(3). If you’re running a slave, its slave number will be used to filter received messages.

The libmodbus implementation of RTU isn’t time based as stated in original Modbus specification, instead all bytes are sent as fast as possible and a response or an indication is considered complete when all expected characters have been received. This implementation offers very fast communication but you must take care to set a response timeout of slaves less than response timeout of master (ortherwise other slaves may ignore master requests when one of the slave is not responding).

Required Methods

Implementors