modbus-pdu

Modbus PDU


This is a generic module to create all the modbus PDU message types. You should then use another abstraction to TCP, RTU and ASCII.

You should not use this directly, use stream instead.

$3

``sh
npm i modbus-pdu
`

$3

`js
var Modbus = require("modbus-pdu");

//
console.log(Modbus.ReadCoils.Request.build(13, 20));
// { address: 13, quantity: 20 }
console.log(Modbus.ReadCoils.Request.parse(new Buffer([ 0x01, 0x00, 0x0d, 0x00, 0x14 ])));

//
console.log(Modbus.ReadFileRecord.Exception.build(Modbus.Exception.ServerDeviceBusy));
// { code: 'ReadFileRecord', exception: 'ServerDeviceBusy' }
console.log(Modbus.Exception.parse(new Buffer([ 0x94, 0x06 ])));

// can also auto detect function code
// { code: "ReadCoils", address: 13, quantity: 20 }
console.log(Modbus.Request(new Buffer([ 0x01, 0x00, 0x0d, 0x00, 0x14 ])));
// { code: 'ReadCoils', data: [ 1, 0, 1, 1, 0, 1, 0, 1 ] }
console.log(Modbus.Response(new Buffer([ 0x01, 0x01, 0xad ])));
`

$3

- 01 ReadCoils(address, quantity)
- 02 ReadDiscreteInputs(address, quantity)
- 03 ReadHoldingRegisters(address, quantity)
- 04 ReadInputRegisters(address, quantity)
- 05 WriteSingleCoil(address, value)
- 06 WriteSingleRegister(address, value)
- 07 ReadExceptionStatus()
- 0B GetCommEventCounter()
- 0C GetCommEventLog()
- 0F WriteMultipleCoils(address, values) // values should be Array of 1/0
- 10 WriteMultipleRegisters(address, values) // values should be Array of 2-size Buffers
- 14 ReadFileRecord(requests) // requests should be Array of objects with keys file, address and length
- 15 WriteFileRecord(requests) // requests should be Array of objects with keys file, address and values (Array of 2-size Buffers)
- 16 MaskWriteRegister(address, andmask, ormask)
- 17 ReadWriteMultipleRegisters(read_address, read_quantity, write_address, values) // values should be Array of 2-size Buffers
- 18 ReadFIFOQueue(address)
- 2B/0E ReadDeviceIdentification(code, id)

$3

- 01 IllegalFunction
- 02 IllegalDataAddress
- 03 IllegalDataValue
- 04 ServerDeviceFailure
- 05 Aknowledge
- 06 ServerDeviceBusy
- 08 MemoryParityError
- 0A GatewayPathUnavailable
- 0B GatewayTargetDeviceFailedToRespond

You can create an Error object with code and message using the following code:

`js
var err = Modbus.Exceptions.error("GatewayPathUnavailable");
console.log(err.code); // 10 (0x0A)
console.log(err.message); // "GatewayPathUnavailable"
``

You can use this error directly when replying to requests using the stream module.