Pioneer WYT RS232 Protocol

Python script that creates and parses the RS232 protocol used by Pioneer WYT mini splits

Overview

The Pioneer WYT mini split works with a $35 Wifi adapter based on the Tuya TYWE1S. This is an ESP8266 flashed with Tuya firmware that uses Tuya's cloud smart home functionality.

It connects to the mini split via a 4-pin connector that has 5V/Gnd and RX/TX for a serial connection. The serial protocol is 9600 8E1 (8 bits, even parity, 1 stop bit).

I managed to reverse how to format command messages to change any HVAC settings, at least on my unit. The first three are important as a handshake! There are still four status messages that I don't understand - neither the message itself nor the response:

4 Unknown Status Messages:

bb000104020100bd
bb00010a03050000b6
bb000109020500b4
bb00010a03050008be

At least three of these change frequently, implying they have status information from the HVAC unit.

Handshake and Issuing Settings

• Connect over serial to the unit
• You must send these 3 messages:
  • A: bb000104020100bd
  • B: bb00010a03050000b6
  • C: bb000109020500b4
• And they are sent as follows:
  • A 3 times
  • B 3 times
  • C 3 times
  • A 5 times
    • I assume this is some kind of synchronization / end of message thing
  • Brief Pause (1/2 second?)
• I'm not sure the exact timing on the pause, I just know that's what the real unit sends
• Once you do the above, you can send a generated temperature control message three times afterwards and it should work
  • If you skip the handshake/heartbeat, it won't work
  • The real unit sends everything 3 times, so I do too
• If you see the exact thing you sent reflected back to you, you've got something wrong
  • If done correctly, you'll get some kind of status response I don't understand

Other Notes

• This is similar to the documented Midea protocol, but different
  • Messages begin with bb rather than aa, for example
• The wifi adapter sends any given command message 3 to 5 times
• Each message from wifi adapter to HVAC gets a result