Unstable communication with Luxtronik heating control unit

[jensrossbach]

Sometimes it happens that communication with the Luxtronik heating control unit becomes unstable. In such a case, the response for specific requests is not received anymore which leads to outdated sensor data as the corresponding sensors are not updated anymore.

The issue happens for different requests but mostly for the requests that are sent later per polling cycle. Sometimes the issue persists for longer time and sometimes it is only shortly visible. Also longer periods (3-4 weeks) without any problem have been observed.

Currently, the root cause of the problem is not known and the issue is under observation. Any support to find the cause of the problem is highly appreciated.

[jensrossbach]

I made a code change that clears the UART buffer before a request is sent to the Luxtronik heating control unit. This change is currently undergoing long-term testing to see if it helps to solve the problem.

[jensrossbach]

Unfortunately the problem occurred again, so this change is not a solution and investigation must continue.

[jensrossbach]

I implemented some robustness improving code like retries and decoupled dataset requests. This change is currently undergoing long-term testing and already looks promising in order to mitigate the UART communication problems.

[jensrossbach]

The robustness improvement measures have been merged to the main branch but I keep this issue open as they do not completely solve the problems, only mitigate them as far as possible. In my tests, the communications was stable for two weeks but other sources still report problems.

[jensrossbach]

Several months of long-term testing now showed that the instable communication has been reduced to a minimum and the robustness measures show positive impacts.

Furthermore, I experienced very instable communication during a short time period when the physical temperature sensor of my heat pump was defect and after the sensor has been replaced, communication was stable again. This indicates that these communication issues are most probably caused by the Luxtronik control unit itself and not by the ESPHome firmware.

Therefore I will close this issue now, but I will pin the issue so that people experiencing communication problems can get some background about this problem.