Modbus RTU sensor, MAX485, Controllino MAXI(Arduino Mega 2560 PLC)

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Nur_Alya

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Hi. I was given a task to do a school project using Controllino MAXI/Arduino Mega 2560 with MAX485 and a Modbus RTU sensor where the objective is to get some reading from the sensor.

Here I am struggling with coding and connection for it. I wanted to ask for advice, opinion on the things I've done with it at the moment. As I am lost with on how to use the one MAX485 as transmitter/receiver in getting values from the sensor to the Controllino.

At the moment;
Sensor: Brown -> External power supply, B -> B MAX485, A -> A MAX485, Black -> GND Controllino
MAX485: DE & RE -> GND, DI -> TX3 Controllino, RO -> RX Controllino, VCC -> 5V RS485 Controllino, GND -> GND Controllino
Controllino : No connection at the moment

Is it true? Or fine with what I am doing at the moment?
 

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Hi,

you need a schematic.
and you need to read modbus specification and go through some tutorials. There are even videos.

Klaus
 

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I expect that existing Arduino MODBUS RTU client examples bring all what you want, as a starting point see

ArduinoModbus - Arduino Reference

The Arduino programming language Reference, organized into Functions, Variable and Constant, and Structure keywords.
www.arduino.cc
 

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Hi,

Short the RE and DE pin in the MAXRS-485 IC and give to one Controller pin to control the Receive/Transmit

If that pin High --> Transmit
If that pin Low --> Receive

Regards,
V. Prakash
 

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