Dark

CQM1H-CPU51 Arduino Modbus RTU

6 posts in this topic

Hi!

First, sorry because bad english.

I want to measure temperatures with arduino and send the values to plc CQM1H-CPU51.

I founded the MODBUS RTU Slave Interface for CQM1-CPU4x/CQM1H CPU51/61 PLC in download section.

I am uploaded the program with dm memory.

For now i want to communicate between pc and plc to try the program, but for now no respons from plc.

I try to communicate with modbus softwares (CAS modbus scanner, Symple Modbus Master, qModMaster), but idon't have respons from plc.

Just lit one a communication led and thats it.

If someone have a functioning example for this type of communication between arduino and CQM1H please answer here.

Or someone use this Modbus rtu ladder program tell me how use it.

Thank you!

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This link will take you to sample programs and explanations of the Modbus RTU protocol by Omron.
https://www.myomron.com/index.php?action=kb&article=1243

It sounds like you are using a sample program for a Modbus RTU Master, so all of the communications will be initiated by the PLC. 
This means that you need to have the arduino set up to be a Modbus RTU Slave. I would start to try to communicate to the arduino using the PC modbus master software to see if you can get communications.
Here are a couple of links explaining Modbus:
https://www.rtaautomation.com/technologies/modbus-rtu/
http://www.simplymodbus.ca/FAQ.htm
Omron Modbus Map for Slaves
http://www.tri-plc.com/appnotes/modbus-map.pdf

The other way to get the information is to use the serial host link communication method. This will utilize the RS232 port on the PLC.
http://etowyzagagexod.tk/547903db83.html
https://forum.arduino.cc/index.php?topic=147526.0

Regards,
Garry

 

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Posted (edited)

Thank You for the answer.

I trying to use CQM1H as Modbus RTU slave.

With this ladder program:

The problem with the host link communication that i need to change run mode to program mode when i want to write dm memory.

 

I will check all the links in your post.

Thank you!

 

Edited by Dark

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18 hours ago, Dark said:

The problem with the host link communication that i need to change run mode to program mode when i want to write dm memory.

The PLC needs to be in Monitor Mode.  Just put it in Monitor mode and leave it in Monitor mode all the time.

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Thank for the answers. I will try monitor mode.

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