kicker

Echo back setting on QJ71C24n - R4

5 posts in this topic

Posted (edited)

Hi everybody.

I have 1 QJ71C24n-R4 with 2 channels CH1 & CH2 and I want to use Modbus RTU for both of channels to read data from electric meter. Now I can do it well with CH2 but cannot with CH1. The reason is echo back setting, my GX work 2 only able to prohibit echo back on CH2, not able on CH1. Does anyone know about this problem? Please give me some advise.

Thank you so much.

Edited by kicker

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This is only possible for Channel two. Can you change your wiring to RS422 ? or just use code to ignore the that was message send if it comes back.

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It's unlucky that I am not able to change my wiring to RS422, it must be Rs485. I am now trying Pre-defined protocol to do the Modbus rtu. Follow your advise, I looked for code to ignore echo back in MELSEC-Q manual, chapter number 8: " DATA COMMUNICATION USING THE PRE-DEFINED PROTOCOL" but It may be not here. Would you please give me some idea or keyword about this code for I can find it easier. Thank you so much for your help.

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Posted (edited)

What I meant with that was that you know the data you have sent so when a message comes back just compare them.

If they are the same don't use it and use the next message.

 

Edited by Gambit

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I see, Thank you so much.

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