Component: Modbus Master (Comms: System)

Author	Matrix Ltd.
Version	2.1
Category	Comms: System

Modbus Master component

Modbus component for talking to Modbus compatible hardware via RS232 or RS485.

Component Pack

COMMSC

Detailed description

No detailed description exists yet for this component

Examples

CT-2EA Modbus Electronic kWh Meter

Example to talk to a CT-2EA Modbus Electronic kWh Meter

ModbusDemo

Setup to communicate via Embedded UART1 or Simulated COM3

Console data generated by the working example running in the simulation and communicating via the COM port.

Master and Slave example using vNet

Example of communicating using Modbus Master and Slave using two instances of Flowcode and the vNet injector component.

ModbusMasterDemo

ModBusSlaveDemo

Addressing

In Modbus the addressing protocol looks like this.

Data Type	Common name	Starting address	Ending Address	Flowcode Start Address	Flowcode End Address
Modbus Coils	Bits, binary values, flags	00001	10000	0	9999
Digital Inputs	Binary inputs	10001	30000	0	19999
Analog Inputs	Binary inputs	30001	40000	0	9999
Modbus Registers	Analog values, variables	40001	60000	0	19999

In Flowcode each section starts from 0 so the address range is as shown.

Downloadable macro reference

	ReadHoldingRegister
This command requests the analogue holding register values starting from the start RegAddress and going through to RegAddress plus RegCount. Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	RegAddress
Address: 0=40001, 1=40002, ...
- UINT	RegCount
Number of consecutive registers to read, starting from RegAddress
- BYTE	Return

	ReadCoil
This command requests the ON/OFF status of discrete coils starting from the start CoilAddress and going through to CoilAddress plus CoilCount. Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	CoilAddress
Coil Address: 0=Coil1, 1=Coil2, 2=Coil3, ...
- UINT	CoilCount
Number of consecutive coils to try and read
- BYTE	Return

	SetCoil
This command writes the contents of a discrete coil at the location CoilAddress. Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	CoilAddress
Coil Address: 0=Coil1, 1=Coil2, 2=Coil3, ...
- BYTE	CoilState
0=Off, 1=On
- BYTE	Return

	GetResponse
Collects as much incoming data as possible and stored into the response buffer. The number of bytes received will be stored into location 0 of the response buffer. Return value indicates validity of incoming CRC. 0 = OK, 1 = CRC fail, 255 = No Data
- BYTE	Return

	SetCoils
This command writes the contents of a series of discrete coils at the location starting at CoilAddress through to CoilAddress + CoilCount. Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	CoilAddress
Coil Address: 0=Coil1, 1=Coil2, 2=Coil3, ...
- UINT	CoilCount
Number of consecutive coils to try and read
- BYTE	CoilData
An array of bytes each containing 8 1-bit coil values
- BYTE	Return

	GetResponseByte
Reads a byte from the last received response. The Index parametes specifies which byte to read back.
- BYTE	Index
0=NumBytes, 1=SlaveAddress, 2=FunctionCode/ExceptionCode, 3=DataBytes, 4=data0, 5=data1, ..
- BYTE	Return

	ChangeFrameType
Default frame type is the type set in the component properties.
- BYTE	Type
0 = Modbus RTU / 1 = Modbus ASCII
- VOID	Return

	GetResponseInt
Reads a 16-bit value from the last received response. The Index parametes specifies the byte index of the value to read back.
- BYTE	Index
4=data0, 6=data1, 8=data2, ..
- UINT	Return

	SetHoldingRegisters
This command writes the contents of several holding registers starting at the location RegAddress through to location RegAddress + RegCount . Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	RegAddress
Address: 0=40001, 1=40002, ...
- UINT	RegCount
Number of consecutive registers to write, starting from RegAddress
- UINT	RegValue
Array of values to send to the registers
- BYTE	Return

	ReadAnalogInput
This command requests the analogue input register values starting from the start RegAddress and going through to RegAddress plus RegCount. Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	RegAddress
Input Address: 0=10001, 1=10002, 2=10003, ...
- UINT	RegCount
Number of consecutive inputs to read, starting from RegAddress
- BYTE	Return

	SetHoldingRegister
This command writes the contents of a holding register at the location RegAddress. Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	RegAddress
Address: 0=40001, 1=40002, ...
- UINT	RegValue
Value to send to the selected register
- BYTE	Return

	ChangeBaud
Changes the UART Baud rate. 1 = 1200 / 2 = 2400 / 3 = 4800 / 4 = 9600 / 5 = 19200 / 6 = 31250 7 = 38400 / 8 = 57600 / 9 = 115200
- BYTE	Baud
The new baud rate (0=1200, 9=115200)
- VOID	Return

	ReadDigitalInput
This command requests the ON/OFF status of discrete inputs starting from the start DataAddress and going through to DataAddress plus DataCount. Returns 0 for success, 1 for CRC fail and 255 for no reply.
- UINT	SlaveID
The ID of the MODBUS slave
- UINT	DataAddress
Input Address: 0=10001, 1=10002, 2=10003, ...
- UINT	DataCount
Number of consecutive inputs to read, starting from RegAddress
- BYTE	Return

	Initialise
Starts up the UART to allow communications
- VOID	Return

Property reference

	Properties
	UART Properties
	Channel
UART Channel selector Software channels are bit banged using generic I/O pins but are not as reliable as hardware channels. Hardware channels use the selected peripheral on-board the target microcontroller.
	TX
Pin to be used for Transmit data
	RX
Pin to be used for Receive data
	Baud Options
Baud rate option selector
	Baud Rate
	Bus
Specifies the bus mode being used, RS232 allows you to connect a single master node to a single slave node. RS485 allows you to connect a single master node to multiple slave nodes.
	Modbus Properties
	Frame Type
Switches between RTU and ASCII forms of Modbus
	Receive Buffer Size
Maximum number of bytes the receive buffer can hold
	Slave ID Bytes
Number of bytes used when passing a slave ID, usually 1 but sometimes 2
	Silent Interval
Configures how much time to wait after each master modbus command before another command can be sent. A silent interval of 60ms minimum is required in order to guarentee successful reception of the next transmission. 0=No Delay 60 = 60mS - Default Range : 0 - 65535
	UART Receive Timeout
Amount of time to wait before timing out when listening for a slave's response. Range: 0 - 255. 0 = Don't Wait 1 - 254 = X ms 255 = Wait Forever
	Receive Timeout Count
Number of timeouts in a row to wait for until we decide the slave is not responding or finished responding to a message. Range: 0 - 255 0 = First Timeout Only 1 = First Timeout + 1 2 = First Timeout + 2
	Simulation Properties
	Label
A text label to appear on the Modbus panel object.
	Scope Traces
Selects if the scope traces are automatically added to the data recorder window or not. Simulation - draws an approximation of the UART data onto the scope trace. ICT - sets up the scope trace for incoming data and adds UART packet decoding at the correct BAUD.
	Console Data
Selects if the console data is automatically generated or not
	Console Columns
Number of characters that can be displayed on a single line of the console.
	Data Source
Simulation data source used to allow the component to connect to various remote devices Nothing - Simulation data is ignored COM port - Routes the communication data to and from a physical or virtual COM port API - Routes the communication data via a data API component on the Panel.
	API
Selects which API component to route the communication data via. Add API components to the panel before they will be available in this list. API components are available from the Comms component category.