Modbus Invalid CRC error

[Joep]

Hello all,

I'm controlling my pool controller by Modbus RTU. Between the Wiser for KNX (Logic Machine) and the pool controller the wiring is about 20 meters. It's a 3 wire connection on both sides and also i'm using terminator resistors 120 Ohm on both sides. I also replaced the cable already but is still keep this Invalid CRC errors.

No my question is if it's allowed to connect the GND to the earth from my installation to see if this might solve the problem or are there any other options left? I already tried swapping the AC wiring as i wrote in another thread but also without luck.

Hope someone can help me out.
Thanks in advance!

Joep

[khalil]

What is the pool controller?

[Joep]

What is the pool controller?

Sugar Valley but it's also known under the name Da-gen or Dryden Aqua.

[Joep]

I'm still strugling with a CRC error. I tried almost everything but without luck. So i was searching the internet for troubleshooting Modbus RTU issues and came across the below wiring diagram. So my question now is if it's needed to use a pull up and a pull down resistor like in the wiring diagram and could this might help to solve the CRC error?

[admin]

Pull up/down resistors are already present on LM (master device). Some slave devices might also have them which can cause communication issues. Try using a USB-RS485 adapter and see if there's any difference compared to the built-in port.

[Joep]

Pull up/down resistors are already present on LM (master device). Some slave devices might also have them which can cause communication issues. Try using a USB-RS485 adapter and see if there's any difference compared to the built-in port.

USB adapter on top of the device is a bit difficult as it will not fit my cabinet. But i found this Modbus RTU to Ethernet interface. I will order one to test if that will solve the CRC error.