Hi All,
I think I am onto something but will need help to confirm. I’ve been reading this post with a lot of interest and I have been putting the puzzle pieces together from posts in this thread.
All of the Midea/Rebranded Midea aircons that has a display board with the 5 pin usb connector unpopulated.

The CN3 connector has the following pins (GND, 5V, TX, REC, 5V/NC depending on model). The TX and REC pins will be shorted together with a 0Ω link. To find this link, follow the send pin (purple dot) of the IR receiver (circled in red) to the CN3 pins. Remove that link and yes, your IR will be dead if you don’t have the USB board plugged in. Also check that the pin next to the ground pin of CN3 has 5V on it. If not follow the outer pin to where there is a open jumper that needs to be bridged.
Plug in your usb adapter board and ESPhome dongle and you are off to the races.

This is where things get interesting though and I will need someone to confirm my theory.

My theory is: The usb breakout board is just a micro controller that converts the serial inputs from the ESPhome dongle to infrared signals and it effectively man in the middles the IR receiver. Hence the reason for the IR not working when the board is unplugged and the jumper on the boards that does not have the C3 connector populated from factory.
Therefore, I believe we do not need the external board and we can get do the following even with the current ESPhome dongles with just a minor software update.
- Create a database of all of the IR signals and a method of sending them out. I believe this has already been done in the ESPhome midea IR remote.
- Read the IR signal onto a buffer and echo it back out on the return pin.
- Be able to send the captured database signals over the return pin
- All this implemented in an update for the Midea ESPhome module.
- We have full feedback with even the option of follow me etc.
This means that we could even make it work with any Midea/rebranded midea aircon that has the 10 pin CN1 connector as the first 3 pins are GND, 5V and the IR signal. Where we just make a jumper harness that man in the middle the CN1 connector. EG intercept the red wire and make most midea/clones smart.
To confirm my theory can someone with the USB breakout board measure the signals on the CN1 connector between GND (black wire) and rec pin (red wire) when controlling it with the IR remote and with the ESPhome dongle.
Unfortunately, I do not have access to a aircon where I can test my theory.
Thank you in advance for your help.
AB