Posted 22 Jun 2017 (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 22 Jun 2017 by kicker Share this post Link to post Share on other sites
Posted 22 Jun 2017 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. Share this post Link to post Share on other sites
Posted 23 Jun 2017 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. Share this post Link to post Share on other sites
Posted 23 Jun 2017 (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 23 Jun 2017 by Gambit Share this post Link to post Share on other sites
