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This tutorial shows how to do a Modbus-RTU communication with the RevPi Connect and an USB-RS485 converter.

Here we are using QModMaster as Modbus Master and the RevPi Connects RS485 interface.

So the PC acts as the Modbus Master and the RevPi Connect acts as the Modbus Slave.

You need the following

• An USB-RS485 Converter

• The software qModMaster

Have a look at the pinout

• Here is an example product, the DIGITUS USB to serial adapter

• Some USB-Serial adaptors have just the two data signal lines, i.e. the USB-RS485 Converter from our shop

Preparation

• Have a look at the tutorial “How to Connect Serial Devices”

  • Connect the RS485+ signal line

  • Connect the RS485- signal line

• Configure the Modbus RTU Slave serial interface as follows

• Save the configuration

• Reset the driver

Instructions

1. Open qModMaster

2. Configure the serial interface parameter

3. Transfer 1,2,3 to the Registers

4. Read it out on the RevPi Connect on the terminal

pi@RevPi14607:~ $ piTest -1 -r Input_1
2 Byte-Value of Input_1: 1 dez (=0001 hex)
pi@RevPi14607:~ $ piTest -1 -r Input_2
2 Byte-Value of Input_2: 2 dez (=0002 hex)
pi@RevPi14607:~ $ piTest -1 -r Input_3
2 Byte-Value of Input_3: 3 dez (=0003 hex)

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