Now the calculator can enter programs, store them to SD card and read them back. Basically, everything works as planned. The English wiki docs is are about 33% cooked here: https://github.com/myak555/MK-52_Resurrect/wiki/6.-AUTO-Mode.-Manual-Calculations./_edit
I have started using the monster as my primary calculator. Based on the experience, some refinements may be needed. In particular, an automatic switch-off after a period of inactivity is a must. Also, it would be nice to allow a WiFi connectivity. I will build a laundry list and then do yet another coding session.
The next big item is to make a full copy of the ESP32 into the C# emulator and release a Windows installer. Now the display is a pixel-to-pixel match: