first init

modbus.go

@@ -0,0 +1,132 @@
+package modbus
+
+import (
+	"fmt"
+)
+
+type pdu struct {
+	unitId       uint8
+	functionCode uint8
+	payload      []byte
+}
+
+type Error string
+
+// Error implements the error interface.
+func (me Error) Error() (s string) {
+	s = string(me)
+	return
+}
+
+const (
+	// coils
+	fcReadCoils          uint8 = 0x01
+	fcWriteSingleCoil    uint8 = 0x05
+	fcWriteMultipleCoils uint8 = 0x0f
+
+	// discrete inputs
+	fcReadDiscreteInputs uint8 = 0x02
+
+	// 16-bit input/holding registers
+	fcReadHoldingRegisters       uint8 = 0x03
+	fcReadInputRegisters         uint8 = 0x04
+	fcWriteSingleRegister        uint8 = 0x06
+	fcWriteMultipleRegisters     uint8 = 0x10
+	fcMaskWriteRegister          uint8 = 0x16
+	fcReadWriteMultipleRegisters uint8 = 0x17
+	fcReadFifoQueue              uint8 = 0x18
+
+	// file access
+	fcReadFileRecord  uint8 = 0x14
+	fcWriteFileRecord uint8 = 0x15
+
+	// customize
+	fcCustomize uint8 = 0x29
+
+	// exception codes
+	exIllegalFunction         uint8 = 0x01
+	exIllegalDataAddress      uint8 = 0x02
+	exIllegalDataValue        uint8 = 0x03
+	exServerDeviceFailure     uint8 = 0x04
+	exAcknowledge             uint8 = 0x05
+	exServerDeviceBusy        uint8 = 0x06
+	exMemoryParityError       uint8 = 0x08
+	exGWPathUnavailable       uint8 = 0x0a
+	exGWTargetFailedToRespond uint8 = 0x0b
+
+	// errors
+	ErrConfigurationError      Error = "configuration error"
+	ErrRequestTimedOut         Error = "request timed out"
+	ErrIllegalFunction         Error = "illegal function"
+	ErrIllegalDataAddress      Error = "illegal data address"
+	ErrIllegalDataValue        Error = "illegal data value"
+	ErrServerDeviceFailure     Error = "server device failure"
+	ErrAcknowledge             Error = "request acknowledged"
+	ErrServerDeviceBusy        Error = "server device busy"
+	ErrMemoryParityError       Error = "memory parity error"
+	ErrGWPathUnavailable       Error = "gateway path unavailable"
+	ErrGWTargetFailedToRespond Error = "gateway target device failed to respond"
+	ErrBadCRC                  Error = "bad crc"
+	ErrShortFrame              Error = "short frame"
+	ErrProtocolError           Error = "protocol error"
+	ErrBadUnitId               Error = "bad unit id"
+	ErrBadTransactionId        Error = "bad transaction id"
+	ErrUnknownProtocolId       Error = "unknown protocol identifier"
+	ErrUnexpectedParameters    Error = "unexpected parameters"
+)
+
+// mapExceptionCodeToError turns a modbus exception code into a higher level Error object.
+func mapExceptionCodeToError(exceptionCode uint8) (err error) {
+	switch exceptionCode {
+	case exIllegalFunction:
+		err = ErrIllegalFunction
+	case exIllegalDataAddress:
+		err = ErrIllegalDataAddress
+	case exIllegalDataValue:
+		err = ErrIllegalDataValue
+	case exServerDeviceFailure:
+		err = ErrServerDeviceFailure
+	case exAcknowledge:
+		err = ErrAcknowledge
+	case exMemoryParityError:
+		err = ErrMemoryParityError
+	case exServerDeviceBusy:
+		err = ErrServerDeviceBusy
+	case exGWPathUnavailable:
+		err = ErrGWPathUnavailable
+	case exGWTargetFailedToRespond:
+		err = ErrGWTargetFailedToRespond
+	default:
+		err = fmt.Errorf("unknown exception code (%v)", exceptionCode)
+	}
+
+	return
+}
+
+// mapErrorToExceptionCode turns an Error object into a modbus exception code.
+func mapErrorToExceptionCode(err error) (exceptionCode uint8) {
+	switch err {
+	case ErrIllegalFunction:
+		exceptionCode = exIllegalFunction
+	case ErrIllegalDataAddress:
+		exceptionCode = exIllegalDataAddress
+	case ErrIllegalDataValue:
+		exceptionCode = exIllegalDataValue
+	case ErrServerDeviceFailure:
+		exceptionCode = exServerDeviceFailure
+	case ErrAcknowledge:
+		exceptionCode = exAcknowledge
+	case ErrMemoryParityError:
+		exceptionCode = exMemoryParityError
+	case ErrServerDeviceBusy:
+		exceptionCode = exServerDeviceBusy
+	case ErrGWPathUnavailable:
+		exceptionCode = exGWPathUnavailable
+	case ErrGWTargetFailedToRespond:
+		exceptionCode = exGWTargetFailedToRespond
+	default:
+		exceptionCode = exServerDeviceFailure
+	}
+
+	return
+}