94 lines
2.7 KiB
Go
94 lines
2.7 KiB
Go
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// Copyright 2014 Quoc-Viet Nguyen. All rights reserved.
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// This software may be modified and distributed under the terms
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// of the BSD license. See the LICENSE file for details.
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/*
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Package modbus provides a client for MODBUS TCP and RTU/ASCII.
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*/
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package modbus
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import (
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"fmt"
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)
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const (
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// Bit access
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FuncCodeReadDiscreteInputs = 2
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FuncCodeReadCoils = 1
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FuncCodeWriteSingleCoil = 5
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FuncCodeWriteMultipleCoils = 15
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// 16-bit access
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FuncCodeReadInputRegisters = 4
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FuncCodeReadHoldingRegisters = 3
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FuncCodeWriteSingleRegister = 6
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FuncCodeWriteMultipleRegisters = 16
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FuncCodeReadWriteMultipleRegisters = 23
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FuncCodeMaskWriteRegister = 22
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FuncCodeReadFIFOQueue = 24
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)
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const (
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ExceptionCodeIllegalFunction = 1
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ExceptionCodeIllegalDataAddress = 2
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ExceptionCodeIllegalDataValue = 3
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ExceptionCodeServerDeviceFailure = 4
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ExceptionCodeAcknowledge = 5
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ExceptionCodeServerDeviceBusy = 6
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ExceptionCodeMemoryParityError = 8
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ExceptionCodeGatewayPathUnavailable = 10
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ExceptionCodeGatewayTargetDeviceFailedToRespond = 11
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)
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// ModbusError implements error interface.
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type ModbusError struct {
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FunctionCode byte
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ExceptionCode byte
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}
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// Error converts known modbus exception code to error message.
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func (e *ModbusError) Error() string {
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var name string
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switch e.ExceptionCode {
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case ExceptionCodeIllegalFunction:
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name = "illegal function"
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case ExceptionCodeIllegalDataAddress:
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name = "illegal data address"
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case ExceptionCodeIllegalDataValue:
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name = "illegal data value"
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case ExceptionCodeServerDeviceFailure:
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name = "server device failure"
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case ExceptionCodeAcknowledge:
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name = "acknowledge"
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case ExceptionCodeServerDeviceBusy:
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name = "server device busy"
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case ExceptionCodeMemoryParityError:
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name = "memory parity error"
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case ExceptionCodeGatewayPathUnavailable:
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name = "gateway path unavailable"
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case ExceptionCodeGatewayTargetDeviceFailedToRespond:
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name = "gateway target device failed to respond"
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default:
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name = "unknown"
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}
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return fmt.Sprintf("modbus: exception '%v' (%s), function '%v'", e.ExceptionCode, name, e.FunctionCode)
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}
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// ProtocolDataUnit (PDU) is independent of underlying communication layers.
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type ProtocolDataUnit struct {
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FunctionCode byte
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Data []byte
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}
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// Packager specifies the communication layer.
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type Packager interface {
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Encode(pdu *ProtocolDataUnit) (adu []byte, err error)
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Decode(adu []byte) (pdu *ProtocolDataUnit, err error)
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Verify(aduRequest []byte, aduResponse []byte) (err error)
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}
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// Transporter specifies the transport layer.
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type Transporter interface {
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Send(aduRequest []byte) (aduResponse []byte, err error)
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}
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