Allocation of PIOs to functions =============================== Test logic ---------- - out TX_ON PC13 u-blox NEO-M8N GPS module connection ------------------------------------ Yellow out UART TX to GPS RX PD8 Orange in UART RX to GPS TX PD9 Debug USART ----------- - out UART TX to PC RX PA2 - in UART RX to PC TX PA3 For the little test board with the 3 LEDs and switches ------------------------------------------------------ Blue in QRP_n PC1 Violet out LED red PC2 Grey in 1750 PC4 White out LED yel PC5 Black - GND GND Brown in RX_n PC6 Red in U_n PC8 Orange out LED grn PC9 Green in D_n PC11 I2C to Audio Codec ------------------ - o codec reset PD4 - - I2S3 MCK PC7 - - I2S3 CK PC10 - - I2S3 SD PC12 - - I2S3 WS PA4 - i/o SDA PB9 - i/o SCL PB6 STM32DISCOVERY onboard things ----------------------------- - out Green LED PD12 - out Orange LED PD13 - out Red LED PD14 - out Blue LED PD15 - in Blue Push Button PA0