[nibeheatpump] NibeGW - Ethernet and RS485 seems to crash each other

[smartbomm]

Expected Behavior

I installed an Arduino Uno with the Arduino Ethernet Shield (https://store.arduino.cc/en-de/products/arduino-ethernet-shield-2?srsltid=AfmBOorOwUoJkPPYgBzSUd0oL02TxyjYAahaIcA_u74KJNjM14wH3xyR) and a JoyIt RS485 Shield (https://joy-it.net/de/products/ARD-RS485) and flashed the NibeGW Code on it. My heat pump is a Nibe SMO40. As I understood, the NibeGW should read the enabled Logging registers from the SMO40 and forward the data from the RS485-Bus over UDP to a specified endpoint. The NibeGW should also answer the packets from the heat pump with an ACK-command that the heat pump doesn't goes into alarm mode.

Current Behavior

I often had the situation, that the heat pump wants to alarm mode because of communication malfunction with the Modbus module. When I removed the Ethernet Shield from the Arduino, than the communication with the heat pump seemed to work. I also observed, that the link status lets of the Ethernet port stopped to blink when I stacked all boards together but when I removed the RS485-Board, the Ethernet module seemed to work.
I thought, maybe it's a hardware issue beacause of the used shields so I ordered an ProDino Ethernet v1 and thought than can't there be a hardware issue because the ProDino is recommended to use. But as I tried yesterday to install the NibeGW on the ProDino and connected it to the home network and the heat pump the heat pump went into alarm mode because of modbus malfunction.

Possible Solution

It seems the software for the ethernet shield and the RS-485 communication aren't compatible because it seems to work with only one of both but both together leads to an alarm on the SMO40.

Steps to Reproduce (for Bugs)

Connect an NibeGW with an SMO40 heat pump and ethernet. And enable the modes module in the heat pump.

Your Environment

• Nibe heat pump with controller SMO40
• NibeGW based on original Arduino Uno with Ethernet and RS485 shield
• Loxberry with nibe-mqtt to translate the UDP-Messages to MQTT