Serial RTU Client

You can create a RTU client channel using the create_rtu_client method. It will immediately try to open the serial port.

note

In Rust, you can use the spawn_rtu_client_task to create a channel and spawn the async task in the context of the current runtime. Outside the Tokio runtime, you can use create_rtu_handle_and_task and manually spawn the returned future.

info

The library does not support sending broadcast requests yet. Sending a request with a broadcast unit ID (0x00) will generate a timeout error, because no server will respond.

Rust

let channel = spawn_rtu_client_task(
    "/dev/ttySIM0",                    // path
    rodbus::SerialSettings::default(), // serial settings
    1,                                 // max queued requests
    default_retry_strategy(),          // retry delays
    DecodeLevel::new(
        AppDecodeLevel::DataValues,
        FrameDecodeLevel::Payload,
        PhysDecodeLevel::Nothing,
    ),
    Some(Box::new(LoggingListener)),
);

C

rodbus_client_channel_t* channel = NULL;
rodbus_decode_level_t decode_level = rodbus_decode_level_nothing();
rodbus_param_error_t err = rodbus_client_channel_create_rtu(runtime,
    "/dev/ttySIM0", // path
    rodbus_serial_port_settings_init(), // serial settings
    1, // max queued requests
    rodbus_retry_strategy_init(),
    decode_level, // decode level
    get_port_listener(),
    &channel
);
if (err) {
    printf("Unable to initialize channel: %s\n", rodbus_param_error_to_string(err));
    return -1;
}

C++

auto channel = rodbus::ClientChannel::create_rtu(
    runtime,
    "/dev/ttySIM0",
    rodbus::SerialPortSettings(),
    1,
    rodbus::RetryStrategy(),
    rodbus::DecodeLevel::nothing(),
    std::make_unique<PrintingPortStateListener>()
);

Java

ClientChannel channel = ClientChannel.createRtu(
        runtime,
        "/dev/ttySIM0", // path
        new SerialPortSettings(), // serial settings
        ushort(1), // max queued requests
        new RetryStrategy(),
        DecodeLevel.nothing(), // decode level
        new PrintingPortStateListener()
);

C#

var channel = ClientChannel.CreateRtu(
    runtime, // runtime
    "/dev/ttySIM0", // path
    new SerialPortSettings(), // serial settings
    1, // max queued requests
    new RetryStrategy(),
    DecodeLevel.Nothing(),
    new PortStateListener()
);

Path

A path to the serial device must be supplied. On Windows, it's generally something like COM3. On Linux, it's generally something like /dev/ttyS3. You need to have the adequate permissions to access these devices.

Serial Port settings

The serial port settings are the following:

• Baud rate in bit per second
• Data bits. Note that Modbus should use 8 data bits.
• Stop bits
• Parity
• Flow control

Maximum Queued Requests

Each channel sends one request at a time and has a fixed-length buffer of requests to send.

Retry Delay

A serial channel tries to open the serial port as soon as it is created. If the serial port cannot be opened, the library automatically waits retry_delay before retrying to open the port.

Decode Level

See logging configuration page for more details.