B4R Code Snippet ModBus RTU

Modbus Function Code Support

Function Code	Register Type
1	Read Coil
2	Read Discrete Input
3	Read Holding Registers
4	Read Input Registers
5	Write Single Coil
16	Write Multiple Holding Registers

    ' initial Paramter
    Modbus.Initial(5,6,2,9600)
    ' Set Registers
    Modbus.CO(0)  = True      ' Coil Register     00000
    Modbus.DI(0)  = True      ' Discrete Input    10001
    Modbus.IR(0)  = 25        ' Input Register    30001
    Modbus.HR(0)  = 50        ' Holding Register  40001
    Modbus.HR(7)  = 100       ' Holding Register  40008

You can use Radzio! Modbus Master Simulator

 

[OGmac]

Delta HMI connection with Servo High Torque Arduino(B4R) via Modbus RTU over Rs485

 

[barx]

Hi @OGmac
I'm looking to create a little project that requires ModBus. I've looked at your Code module above and have a question.

Can it only 'Set' Registers? I can see subs that are named as though they receive data but:

1. They are private subs, as though they are for internal use only.
2. Following the code, if you make one of the subs public and call it (not actually run the code yet) it seems as though it writes to the stream and then when data is received, it would call the sub again in the select case statement.

Maybe I am just reading it wrong and not fully understanding the ModBus protocol.

If the code module is able to read registers, could you give a simple example of how it is done?

Thanks

 

[OGmac]

Hi @OGmac
I'm looking to create a little project that requires ModBus. I've looked at your Code module above and have a question.

Can it only 'Set' Registers? I can see subs that are named as though they receive data but:

1. They are private subs, as though they are for internal use only.
2. Following the code, if you make one of the subs public and call it (not actually run the code yet) it seems as though it writes to the stream and then when data is received, it would call the sub again in the select case statement.

Maybe I am just reading it wrong and not fully understanding the ModBus protocol.

If the code module is able to read registers, could you give a simple example of how it is done?

Thanks

If I understand correctly, your goal is to read the registers of a device. For this purpose, you need a code that is in Master mode, but the above code is related to the slave mode. To better understand modbus, I suggest you read this website.
http://www.simplymodbus.ca/index.html

 

[peacemaker]

What is the exact pinout of MAX485 board in this circuit diagram ? I mean how exactly controlled the direction ?

 

[OGmac]

What is the exact pinout of MAX485 board in this circuit diagram ? I mean how exactly controlled the direction ?

    Private RS485    As Pin
    Private Send     As Boolean = True
    Private Recv     As Boolean = False  
.
.
.
'Tx  Transmition Pin RS485
'Rx  Recive      Pin RS485
'Dir Dirction    Pin RS485
'Buad Rate       RS485
Public Sub Initial(Rx As Byte,Tx As Byte,Dir As Byte,BudeRate As ULong)
    softserial.Initialize(BudeRate, Rx, Tx)
    sstream.Initialize(softserial.Stream, "Sstream_newdata", Null)
    RS485.Initialize(Dir,RS485.MODE_OUTPUT)
    RS485.DigitalWrite(Recv)
End Sub

 

[peacemaker]

    Private RS485    As Pin
    Private Send     As Boolean = True
    Private Recv     As Boolean = False 
.
.
.
'Tx  Transmition Pin RS485
'Rx  Recive      Pin RS485
'Dir Dirction    Pin RS485
'Buad Rate       RS485
Public Sub Initial(Rx As Byte,Tx As Byte,Dir As Byte,BudeRate As ULong)
    softserial.Initialize(BudeRate, Rx, Tx)
    sstream.Initialize(softserial.Stream, "Sstream_newdata", Null)
    RS485.Initialize(Dir,RS485.MODE_OUTPUT)
    RS485.DigitalWrite(Recv)
End Sub

What pins are on the MAX485 board ?

 

[OGmac]

View attachment 117757

What pins are on the MAX485 board ?

'Tx Transmition Pin RS485 Pin 5
'Rx Recive Pin RS485 Pin 6
'Dir Dirction Pin RS485 Pin 2
'Buad Rate RS485

Modbus.Initial(5,6,2,9600)

 

[peacemaker]

My question is about blue board pins - what is yellow connected 2 pins ? What is the blue board ?

Now there are RS485 converter board with just Tx, Rx and GND pins.

 

[OGmac]

 

[peacemaker]

Thanks. But how to use with such adapter ? Without direction.

 

[OGmac]

THanks. BUt how to use with such adapter ?
View attachment 117759

In this model, the converter automatically sends and receives switches and you do not need pin 2, do not use that pin safely .