I was testing the RS485 Circuit, below is my circuit and I connect J5 to my PC using another RS485 to USB converter. In PC through Modscan software I was monitoring the polling and response, a twisted wire used, length of wire is 3 feet only. I observe the polling missing some time, generally out of 100 polls, I missed three response. my PC is master and device is Slave. So I probe the waveforms and observe while in receiving mode I saw a lot of noise on RS485 waveforms. and when transmitting mode such noise is not there. see the attached waveform, does any have any idea, this is how an RS485 behave. any suggestion, advise.
The ground layout looks wrong. The break between signal ground and field ground should run under U3 splitting it half.
Looking at the schematic, keep everything to the left of U3 over the signal ground. Keep everything to the right of U3 over the field ground. The way it shown it does not make sense.