Component: Modbus Slave (Comms: System)

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Author Matrix Ltd.
Version 2.0
Category Comms: System


Modbus Slave component

Modbus component for creating Modbus compatible slave hardware via RS232 or RS485.

Component Source Code

Please click here to download the component source project: FC_Comp_Source_ModbusSlave.fcfx

Please click here to view the component source code (Beta): FC_Comp_Source_ModbusSlave.fcfx

Detailed description

No detailed description exists yet for this component

Examples

Example master program to control the slave. The example reads the 8 switches connected to PortD. If the switch values change then the new value is send to the slave.

FC6 Icon.png Modbus Master Example


Example slave program to react to the signals from the master. The example listens for Modbus commands from the master and outputs the current coils 0-7 state to eight LEDs connected to PortD.

FC6 Icon.png Modbus Slave Example


Master and Slave example using vNet

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

FC6 Icon.png ModbusMasterDemo

FC6 Icon.png 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.






Macro reference

ChangeBaud

Fc9-comp-macro.png ChangeBaud
Changes the UART Baud rate. 1 = 1200 / 2 = 2400 / 3 = 4800 / 4 = 9600 / 5 = 19200 / 6 = 31250 7 = 38400 / 8 = 57600 / 9 = 115200 
Fc9-u8-icon.png - BYTE Baud
The new baud rate (0=1200, 9=115200) 
Fc9-void-icon.png - VOID Return


ChangeFrameType

Fc9-comp-macro.png ChangeFrameType
Default frame type is the type set in the component properties. 
Fc9-u8-icon.png - BYTE Type
0 = Modbus RTU / 1 = Modbus ASCII 
Fc9-void-icon.png - VOID Return


CheckForIncoming

Fc9-comp-macro.png CheckForIncoming
Checks for an incoming message and if the data address is within range then also automatically replies with the correct reply. Returns 0 if no comms received, 1 for a succesful transaction, 255 for an error. 
Fc9-u8-icon.png - BYTE Return


GetLastIncoming

Fc9-comp-macro.png GetLastIncoming
Gets a value from the last incoming command. Index 0 = 0 Read / 1 Write Index 1 = 0 Coils / 1 DigInput / 2 AnInput / 3 Register Index 2 = Address Index 3 = Number 
Fc9-u8-icon.png - BYTE Index
Range: 0-3 
Fc9-u16-icon.png - UINT Return


Initialise

Fc9-comp-macro.png Initialise
Starts up the UART to allow communications and initialises the states of the various Modbus Coils, Inputs and Registers to 0. 
Fc9-void-icon.png - VOID Return


ReadAnalogInput

Fc9-comp-macro.png ReadAnalogInput
Reads the value of a single analogue input. 
Fc9-u16-icon.png - UINT Address
Coil Address 
Fc9-u16-icon.png - UINT Return


ReadCoils

Fc9-comp-macro.png ReadCoils
Reads the state of up to eight digital coils. Can pack a max of 8-bits together in a single operation 
Fc9-u16-icon.png - UINT StartAddress
Coil Address Range 0 to (NumCoils - 1) 
Fc9-u8-icon.png - BYTE AddressCount
Range 1-8 
Fc9-u8-icon.png - BYTE Return


ReadDigitalInputs

Fc9-comp-macro.png ReadDigitalInputs
Reads the state of up to eight digital inputs. Can pack a max of 8-bits together in a single operation 
Fc9-u16-icon.png - UINT StartAddress
Coil Address Range 0 to (NumCoils - 1) 
Fc9-u8-icon.png - BYTE AddressCount
Range 1-8 
Fc9-u8-icon.png - BYTE Return


ReadHoldingRegister

Fc9-comp-macro.png ReadHoldingRegister
Reads the value of a single holding register. 
Fc9-u16-icon.png - UINT Address
Coil Address 
Fc9-u16-icon.png - UINT Return


SetAnalogInput

Fc9-comp-macro.png SetAnalogInput
Sets the state of a single analogue input. 
Fc9-u16-icon.png - UINT Address
Coil Address 
Fc9-u16-icon.png - UINT Value
Analogue Value range 0 - 65535 
Fc9-void-icon.png - VOID Return


SetBaudRate

Fc9-comp-macro.png SetBaudRate
Allows the Baud Rate to be controlled dynamically overriding the default rate specified by the Baud component property. 
Fc9-u8-icon.png - BYTE Rate
0=1200, 1=2400, 2=4800, 3=9600, 4=19200, 5=38400, 6=57600, 7=115200 
Fc9-void-icon.png - VOID Return


SetCoil

Fc9-comp-macro.png SetCoil
Sets the state of a single digital coil. 
Fc9-u16-icon.png - UINT Address
Coil Address 
Fc9-u8-icon.png - BYTE State
0=off, 1=on 
Fc9-void-icon.png - VOID Return


SetDigitalInput

Fc9-comp-macro.png SetDigitalInput
Sets the state of a single digital input. 
Fc9-u16-icon.png - UINT Address
Coil Address 
Fc9-u8-icon.png - BYTE State
0=off, 1=on 
Fc9-void-icon.png - VOID Return


SetHoldingRegister

Fc9-comp-macro.png SetHoldingRegister
Sets the state of a single holding register. 
Fc9-u16-icon.png - UINT Address
Coil Address 
Fc9-u16-icon.png - UINT Value
Analogue Value range 0 - 65535 
Fc9-void-icon.png - VOID Return


SetSlaveAddress

Fc9-comp-macro.png SetSlaveAddress
Allows the slave address to be overridden from the default slave address specified in the component property. The number of bytes used for the address is fixed by the Slave ID Bytes property to save on RAM usage. 
Fc9-u16-icon.png - UINT SlaveAddress
 
Fc9-void-icon.png - VOID Return


Property reference

Fc9-prop-icon.png Properties
Fc9-conn-icon.png UART Properties
Fc9-type-16-icon.png 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. 
Fc9-type-5-icon.png TX
Pin to be used for Transmit data 
Fc9-type-5-icon.png RX
Pin to be used for Receive data 
Fc9-type-16-icon.png Baud Options
Baud rate option selector 
Fc9-type-14-icon.png Baud Rate
 
Fc9-type-16-icon.png 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. 
Fc9-type-21-icon.png Timeout
Timeout in milliseconds used to dictate the maximum time to wait in milliseconds between bytes in a packet. Range: 1 - 255 
Fc9-conn-icon.png Modbus Properties
Fc9-type-16-icon.png Frame Type
Switches between RTU and ASCII forms of Modbus 
Fc9-type-21-icon.png Receive Buffer Size
Maximum number of bytes the receive buffer can hold 
Fc9-type-21-icon.png Slave ID Bytes
Number of bytes used when passing a slave ID, usually 1 but sometimes 2 
Fc9-type-21-icon.png Slave Address
 
Fc9-type-21-icon.png Reply Delay
Delay in micro seconds to wait before transmitting a reply 
Fc9-type-7-icon.png Maintain Stats
Controls if the last command from the master is logged allowing for easier value updates. No - Do not log commands Yes - Commands are logged and available via the GetLastIncoming macro 
Fc9-conn-icon.png Simulation Properties
Fc9-type-10-icon.png Label
A text label to appear on the Modbus panel object. 
Fc9-type-7-icon.png 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. 
Fc9-type-7-icon.png Console Data
Selects if the console data is automatically generated or not 
Fc9-type-21-icon.png Console Columns
Number of characters that can be displayed on a single line of the console. 
Fc9-type-16-icon.png 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. 
Fc9-type-16-icon.png 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. 
Fc9-conn-icon.png Modbus Coils - Single bit values
Fc9-type-21-icon.png Starting Address
Start address of the Modbus coils. Referenced from 0. For example Slave 1 might have 100 coils addressed 0-99 Start Address = 0 Slave 2 might have 100 coils addressed 100-199 Start Address = 100 
Fc9-type-21-icon.png Number of Addresses
Specifies how many Coils are available on the slave. Each address consumes a single bit of RAM, 8 Addresses are packed together into a single RAM Byte. 
Fc9-conn-icon.png Digital Inputs - Single bit values
Fc9-type-21-icon.png Starting Address
Start address of the Modbus digital inputs. Referenced from 0. For example Slave 1 might have 100 inputs addressed 0-99 Start Address = 0 Slave 2 might have 100 inputs addressed 100-199 Start Address = 100 
Fc9-type-21-icon.png Number of Addresses
Specifies how many Digital Inputs are available on the slave. Each address consumes a single bit of RAM, 8 Addresses are packed together into a single RAM Byte. 
Fc9-conn-icon.png Analog Inputs - 16-bit values
Fc9-type-21-icon.png Starting Address
Start address of the Modbus analogue inputs. Referenced from 0. For example Slave 1 might have 100 inputs addressed 0-99 Start Address = 0 Slave 2 might have 100 inputs addressed 100-199 Start Address = 100 
Fc9-type-21-icon.png Number of Addresses
Specifies how many 16-bit analogue inputs are available on the slave. Each address consumes two RAM Bytes. 
Fc9-conn-icon.png Holding Registers - 16-bit values
Fc9-type-21-icon.png Starting Address
Start address of the Modbus registers. Referenced from 0. For example Slave 1 might have 100 registers addressed 0-99 Start Address = 0 Slave 2 might have 100 registers addressed 100-199 Start Address = 100 
Fc9-type-21-icon.png Number of Addresses
Specifies how many 16-bit holding registers are available on the slave. Each address consumes two RAM Bytes.