Logamatic 4122 not detected despite correct wiring and manual pin config (FW 3.7.2)

[halodrian]

Hello EMS-ESP Team,

I'm unable to get my Buderus heating system controller detected and hope you can help me identify the issue.

My System:

Gateway Hardware: Ai-Thinker ESP32-S module

Gateway Firmware: v3.7.2 (clean flashed)

Heating Controller: Buderus Logamatic 4122 (Firmware v8.21) on a Buderus GB162 Boiler

Full System: Includes solar thermal, a second heating circuit (HC2), and a hydraulic diverter.

The Problem:
The gateway does not detect the Logamatic 4122 controller. Initially, it was able to receive a high number of telegrams with almost zero errors, but only the boiler was detected. After trying different board profiles, the gateway stopped receiving any data ("EMS Bus disconnected").

Troubleshooting Steps (without success):

Wiring: Polarity of the bus wires was swapped. This resulted in zero telegrams being received, so it was swapped back to the initial, working state.

Board Profiles: We tried all available board profiles. All of them resulted in a "disconnected" state.

Manual Pin Configuration: The only way to receive data again was to set the board profile to "Custom" with the known correct pins for my board: Rx GPIO: 17 and Tx GPIO: 16.

Tx Mode: We tried both "EMS" and "EMS+" modes in combination with the manual pin configuration.

Clean Flash: The gateway was completely erased and clean-flashed with the latest firmware (v3.7.2) via USB.

Current State:
Even after a clean flash and setting the correct manual pin configuration (Rx:17, Tx:16, Profile: Custom, Mode: EMS+), the gateway remains in the "EMS Bus disconnected" state and does not receive any telegrams.

Since the bus connection was proven to be physically working at the beginning and all software/configuration options have been exhausted, this strongly points towards a hardware defect on the gateway's EMS interface or a deep incompatibility.

Do you have any final ideas or is this a known issue? Thank you for your amazing project!

[proddy]

We know EMS-ESP works with the Buderus GB162 so don't expect it's a software issue. What gateway board are you using and what additional memory are you using with the ESP32-S chip?

(moving this to a discussion)

[MichaelDvP]

Looking at https://bbqkees-electronics.nl/ems-device-compatibility/
shows that Ecomatic 4000 series is listed as incompatible: no meaningful interaction.
Maybe some boiler parameters when connection th the GB162 EMS, but i don't know this system.

[MichaelDvP]

The Logamatic is detected as a cascade modul with no product-id. It reads all parameters and values from boiler and sends command message 0x1A: connect(0x0C) W boiler(0x08), UBASetPoints(0x1A), data: 00 00 00 00
But it does not publsh any own value on the bus.
Please check: log all and change a value on the thermostat, e.g. temperature setpoint. If we can see it as a broadcast connect(0x0C) B all(0x00)...., we can try to add these telegrams.

[halodrian]

Thank you for the analysis and the clear instructions.

I have generated a new trace log as you requested.

During the logging period, I manually changed several different parameters on the MEC2 control unit to generate more varied telegrams. This included switching between operating modes (e.g., Winter/Summer, Auto/Day/Night) and changing temperature setpoints.

The new log file is attached.

Hopefully, you can find the broadcast telegrams in this log. Please let me know if you need any other data.

log.txt
log(1).txt

[MichaelDvP]

Sorry, there are no values from the thermostat. it calculates all values internally and only sends the boiler command.
Try with the KM200. If this gives more values, log with the ems-esp and let us know. Then we can implement the same logic.
But i think the KM200 is also limited, so make sure you can return the KM200 if you get no other values.

[MichaelDvP]

Maybe a better choice: get a used RC35 from ebay.

[halodrian]

Thank you very much for the final, clear analysis.

Even though it's not the result I was hoping for, it's a definitive answer that saves me from wasting more time. This is very helpful.

I will now try the official KM200 gateway as you suggested.

I really appreciate your time and support. Keep up the great work on this project!