Class Modbus

Namespace

Pamoja.Modbus

Assembly

Pamoja.Modbus.dll

Modbus RTU framing for RS485 field devices.

public static class Modbus

Inheritance

object

Modbus

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

object.ToString()

Remarks

Modbus over RS485 is what cheap industrial sensing speaks: energy meters, soil probes, water-quality transmitters, pump controllers. Each request builder returns a complete frame with its CRC, ready to write to a port, and a reply comes back through ParseFrame(ReadOnlySpan<byte>) as an object that reads its own values.

Methods

Crc16(ReadOnlySpan<byte>)

Computes the CRC-16/MODBUS that every RTU frame ends with.

public static ushort Crc16(ReadOnlySpan<byte> bytes)

Parameters

bytes ReadOnlySpan<byte>

The frame contents, without the trailing checksum.

Returns

ushort

The checksum.

ParseFrame(ReadOnlySpan<byte>)

Parses a received RTU frame, verifying its CRC.

public static ModbusFrame ParseFrame(ReadOnlySpan<byte> bytes)

Parameters

bytes ReadOnlySpan<byte>

The frame as it came off the wire, checksum included.

Returns

ModbusFrame

The validated frame, which reads its own registers and coils.

Exceptions

PamojaException

The frame is truncated, oversized, or its CRC does not match its contents.

Raw(byte, byte, ReadOnlySpan<byte>)

Builds a request from a raw function code and data.

public static byte[] Raw(byte address, byte functionCode, ReadOnlySpan<byte> data)

Parameters

address byte

The unit address to send to.

functionCode byte

The function code byte.

data ReadOnlySpan<byte>

The bytes that follow it, used verbatim.

Returns

byte[]

The frame to send.

Remarks

The escape hatch for the function codes this SDK does not name.

Exceptions

PamojaException

The data is longer than a PDU may be.

ReadCoils(byte, ushort, ushort)

Builds a read-coils request (function 0x01).

public static byte[] ReadCoils(byte address, ushort start, ushort count)

Parameters

address byte

The unit address to ask.

start ushort

The address of the first coil.

count ushort

How many coils to read.

Returns

byte[]

The frame to send.

Exceptions

PamojaException

The native call failed.

ReadDiscreteInputs(byte, ushort, ushort)

Builds a read-discrete-inputs request (function 0x02).

public static byte[] ReadDiscreteInputs(byte address, ushort start, ushort count)

Parameters

address byte

The unit address to ask.

start ushort

The address of the first input.

count ushort

How many inputs to read.

Returns

byte[]

The frame to send.

Exceptions

PamojaException

The native call failed.

ReadHoldingRegisters(byte, ushort, ushort)

Builds a read-holding-registers request (function 0x03).

public static byte[] ReadHoldingRegisters(byte address, ushort start, ushort count)

Parameters

address byte

The unit address to ask.

start ushort

The address of the first register.

count ushort

How many registers to read.

Returns

byte[]

The frame to send.

Exceptions

PamojaException

The native call failed.

ReadHoldingRegistersReply(byte, ReadOnlySpan<ushort>)

Builds the reply a device sends to a read-holding-registers request.

public static byte[] ReadHoldingRegistersReply(byte address, ReadOnlySpan<ushort> values)

Parameters

address byte

The unit address the reply comes from.

values ReadOnlySpan<ushort>

The register values the device reports, in address order.

Returns

byte[]

The frame the device would send.

Remarks

This is the answering half of ReadHoldingRegisters(byte, ushort, ushort), so a client can be written and tested against what a device sends without a device on the line.

Exceptions

PamojaException

There are no values, or too many for one frame.

ReadInputRegisters(byte, ushort, ushort)

Builds a read-input-registers request (function 0x04).

public static byte[] ReadInputRegisters(byte address, ushort start, ushort count)

Parameters

address byte

The unit address to ask.

start ushort

The address of the first register.

count ushort

How many registers to read.

Returns

byte[]

The frame to send.

Exceptions

PamojaException

The native call failed.

ReadInputRegistersReply(byte, ReadOnlySpan<ushort>)

Builds the reply a device sends to a read-input-registers request.

public static byte[] ReadInputRegistersReply(byte address, ReadOnlySpan<ushort> values)

Parameters

address byte

The unit address the reply comes from.

values ReadOnlySpan<ushort>

The register values the device reports, in address order.

Returns

byte[]

The frame the device would send.

Exceptions

PamojaException

There are no values, or too many for one frame.

WriteMultipleCoils(byte, ushort, ReadOnlySpan<bool>)

Builds a write-multiple-coils request (function 0x0F).

public static byte[] WriteMultipleCoils(byte address, ushort start, ReadOnlySpan<bool> values)

Parameters

address byte

The unit address to write to.

start ushort

The address of the first coil.

values ReadOnlySpan<bool>

One state per coil, at most 1968 of them.

Returns

byte[]

The frame to send.

Exceptions

PamojaException

There are no values, or more than one request can carry.

WriteMultipleRegisters(byte, ushort, ReadOnlySpan<ushort>)

Builds a write-multiple-registers request (function 0x10).

public static byte[] WriteMultipleRegisters(byte address, ushort start, ReadOnlySpan<ushort> values)

Parameters

address byte

The unit address to write to.

start ushort

The address of the first register.

values ReadOnlySpan<ushort>

The 16-bit values, at most 123 of them.

Returns

byte[]

The frame to send.

Exceptions

PamojaException

There are no values, or more than one request can carry.

WriteSingleCoil(byte, ushort, bool)

Builds a write-single-coil request (function 0x05).

public static byte[] WriteSingleCoil(byte address, ushort coil, bool on)

Parameters

address byte

The unit address to write to.

coil ushort

The coil address.

on bool

The state to write.

Returns

byte[]

The frame to send.

Exceptions

PamojaException

The native call failed.

WriteSingleRegister(byte, ushort, ushort)

Builds a write-single-register request (function 0x06).

public static byte[] WriteSingleRegister(byte address, ushort register, ushort value)

Parameters

address byte

The unit address to write to.

register ushort

The register address.

value ushort

The 16-bit value to write.

Returns

byte[]

The frame to send.

Exceptions

PamojaException

The native call failed.