Bernard, that is some awesome piece of work! Thanks for sharing the detailled pictures and all the effort you have put into this!
As the original mainboard has a water damage and a replacement costs >500€, I will definitely fix / upgrade my MI632 based on your design!
Never the less, there are some questions I have (right now - there's most likely more to come ;-) ):
1. Would it be possible to recieve the STLs of the 3D-Printed parts you used? This would make life easier, as I will not have to design them myself...
2. Would it be possible to recieve the configs you used for setting up the robot? (Or simply images of the Teensy and Raspi SD-Cards and the sketch for the ESP32?)
3. Are you using the original battery and charger? (If not: what are you using?)
4. Are you using some kind of odometry? Or is it "included" in the brushless motors?
5.1 At what distance from the center line have you installed the perimeter sensors?
5.2 Have you just left the perimeter wire at the original distance of about 30cm from the edges of the lawn?
6. What Resistor values are you using for R1, R2, R7 and R8? (2k and 1k as in the bom?)
7. (Maybe a "noob"-question) What is the "ARU"?
Again: Thanks for sharing this - this is really helpfull! I will also share my progress on the conversion.