hi, board is STM32F103C8T6 from ebay... I bought it and i must say : "it is piece of crap". Errata sheet is long as toilet paper. I spend a few days trying ADC manage to work but, no... simply no.... internal capacitor from AD integrator inject huuuuge amount of noise to ADC input (ADC1,ADC2, all channels !!! ) and it cause 1,6V offset (with 100k load on inputs drop to 0,6V). I2C is almost unusable. And so on...
for me, bad choice