Prototyping on breadboard has been done. I'm using USBasp to program the ATTiny1634 using the Arduino software. So far the simplest way how to get the results.

• ADC values jump so this needs some tweaking and filtering
• I don't know why but the Arduino core works bit strange using internal 1V1 reference. The ADC input then works in 8b resolution that overflows to higher byte when the input is high enough. It looks like the analogRead() method is badly implemented.
• I'm using softI2Cmaster library to get the OLED display working. So far works great