A while ago I got a nice USB current/voltage meter as described here
Curious to see how it worked, I opened it up - and then it never worked again. The OLED screen turns on but nothing is displayed. Looking at the TSSOP20 chip, I thought it might be an STM8 or STM32F0 which I could debug or reprogram. It turned out not to be, although the pinout is extremely close.