This class implements the Modbus RTU protocol, allowing communication with Modbus devices such as industrial controllers and PLCs.
The following Modbus commands are implemented:
| Command | Description |
|---|---|
| 0x01 | Read Coils |
| 0x02 | Read Discrete Inputs |
| 0x03 | Read Holding Registers |
| 0x04 | Read Input Registers |
| 0x05 | Write Single Coil |
| 0x06 | Write Single Registers |
| 0x0F | Write Multiple Coils |
| 0x10 | Write Multiple Registers |
modbus <- Modbus(hardware.uart12, 9200, 8, PARITY_NONE, 1, callbackHandler, errorHandler, 1.0);| # | Type | Description |
|---|---|---|
| 1 | uart | Unconfigured UART pins |
| 2 | integer | Baud Rate |
| 3 | integer | Data bits (7 or 8) |
| 4 | const | PARITY_NONE / PARITY_EVEN / PARITY_ODD |
| 5 | integer | Stop bits (1 or 2) |
| 6 | function | Receive callback |
| 7 | function | Error callback |
| 8 | float | Response timeout in seconds (optional) |
function errorHandler(functionCode, exceptionCode) {
server.error(format("Function: 0x%02X, Exception: 0x%02X", functionCode, exceptionCode));
// Handle some errors
}
function callbackHandler(data) {
// Generic handler for callbacks from read functions
// See function definition for 'data' argument format
}Description: Reads status of 1-2000 contiguous coils in a single device.
Callback argument: blob of length (quantity / 8), rounded up, one coil per bit, LSB->MSB (as per Modbus spec)
Description: Reads status of 1-2000 contiguous inputs in a single device
Callback Argument: blob of length (quantity / 8), rounded up, one input per bit, LSB->MSB (as per Modbus spec)
Description: Read the values of up to 125 contiguous 16-bit holding registers
Callback Argument: big-endian blob of length (quantity * 2), beginning with the startingAddress register
Description: Read the values of up to 125 contiguous 16-bit input registers
Callback Argument: big-endian blob of length (quantity * 2), beginning with the startingAddress register
Description: Writes a single coil
Arguments: coilValue argument is 0 (off) or 1 (on)
Description: Writes a single register
Argument: regValue argument is a 16-bit value (anything >16 bits will be truncated to the least sig. 16 bits)
Description: Write up to 1968 coils in a single device
Argument: coilValues argument should be a blob, startingAddress coil at LSB of first byte
Description: Write up to 123 registers in a single device
Argument: regValues argument should be a big-endian blob of length (quantity * 2) and begin with the 16-bit value of startingAddress