I received my EW11 about a week ago and have been trying to get it working, but so far without any success.
I’m fairly certain that the wires labeled A and B are not the Modbus connection, but are only powering the display. I measure a constant ~10 V AC on those terminals.
When I connect P and Q to the A and B terminals of the EW11, nothing happens when I try to scan for registers (using your Python script). I also tried swapping the wires, but unfortunately that didn’t change anything.
When measuring the voltage between the P and Q terminals, I see it jump to about 3 V and then drop back to zero after a few seconds. This cycle repeats roughly every 5 seconds. When I measure between P and E (yellow wire), or Q and E, I get about half that voltage. Because of this, I’m fairly confident that the yellow wire (E) is ground.
I also found a Reddit post (where I believe you commented as well: https://www.reddit.com/r/Esphome/comments/1009nsg/modbus_logger_midea_chromagen_heat_pump_hot_water/?show=original) showing a picture of a PCB that looks very similar to mine. In that image, the display connects to two PCB connectors that are not labeled. However, the picture also shows another connector (CN21) exposing P, Q, and E, with “to computer” written underneath it.
I checked my schematic and CN21 is not shown there. However, it does appear to exist on my PCB, just without a connector soldered onto it.
Do you think the PQE connection going to the display is the same as the missing CN21 connector? It seems like a big coincidence that PQE would be labeled in the schematic as going to the display, yet not be the Modbus connection.
Do you have any ideas on how I could move forward from here? I really want to get this working, and any help would be greatly appreciated.
