PA0-PA7 -> GPIO [7:0]
PA9 -> UART TX
PA10 -> UART RX
PB6-PB9 -> PWM1, PWM2
PB10 -> I2C SCL
PB11 -> I2C SDA
PB12 -> SPI SS
PB13 -> SPI CLK
PB14 -> SPI MISO
PB15 -> SPI MOSI
if PA15 == 0 then this device acts as USB<->UART transceiver