Hi, I’m having trouble with an RS-485 connection. I’ve been stuck on it for quite a while because I’m switching from Click Automation to Siemens, and it’s evidently a bit more complicated here.

I have a fan set to 19200 baud, 8 data bits, even parity, and 1 stop bit. For a long time only the Tx LED was blinking. I originally wired the fan to the PLC A-to-A and B-to-B. I then swapped the wires—A to B and B to A on the PLC—and at that moment communication started; both Tx and Rx are blinking. If I change the parity or the ID, Rx stops blinking, so the link is clearly active. However, I’m now getting error 81E9, which should be a CRC problem, and after about three days I’m out of ideas.

I have tried many times to start with Bool, or first scan, or timer, now you can see attached a clock but does not work.

Do you have any advice? Screenshots are at link below: []

the forum has a powerful search function: links for 81E9

a possible solution is to extend the RESP_TO parameter, as the message might be cutoff before it comes through completely, therefore invalidating or missing the CRC entirely