Re:Launch HN: Electric Air (YC W23) – Heat pump sold directl...
by briHass on Monday March 13, 2023 @09:22PM
(#35146030)
Can you provide any more details on the I2C interface on Midea units?
I found some sparse documentation on Midea's (and rebadged units) Modbus-esque protocol over RS485 (aka XYE connectors), and I control it via an ESP32 on HA. From the indoor unit, the diagnostic data I could reverse engineer is limited to temp sensors (intake, indoor coil, outdoor ambient) and basic running modes. I believe the outdoor unit also has a modbus/485 that has more info, and obviously the signal wire passes some comms between the two, but Midea doesn't make this stuff public.
1) Detailed diagnostics i.e. RPMs, feeds, speeds, currents, temps etc can be read from the high voltage signal line between the indoor and outdoor unit - there is an official tool (search "Dr. Smart Midea" that does this)
2) The outdoor unit can be driven manually using the same tool using an i2c port that is on the PCB on the outdoor unit
I have the new generation of their Dr. Smart tool, which I haven't had the time to thoroughly test or document. If there is interest I will likely try to reverse engineer and document these protocols properly.
> "I want to be my own mechanic, and if I'm not that mechanic I want to be able to have anyone be that mechanic."
> "Do you want to know what the active airflow rate is? I want to know what the active airflow rate is. Do you want to know power consumption? I want to know power consumption. Do you have a way to write unique schedules/programs that get executed on the heat pump? I want a way to write unique schedules/programs that get executed on the heat pump."
There's one feature of this diagnostic interface that I really really like. It allows you to "drive" the hardware of the unit manually, like Program Auto mode on a camera. You can manually set the frequency of the compressor and fan, and the control board will continue to enforce safeties.
I haven't tried yet, but something I really want to try to implement myself is "frequency lockout". This is a common feature on commercial variable frequency drives. I noticed that under some operating conditions, the unit vibrations resonate with the building and create unpleasant sounds - I'd like to program it to never dwell on that frequency and skip over it.
> The desire is to have any control/knowledge you'd want to have as the creator/developer.
While I was exploring this, I had this in mind constantly. I definitely had this diag interface in mind when I was selecting a unit.