Intention

By default the UART2 is connected to the virtual COM of the ST-Link. The same UART is possible to connect to the Arduino connector.

So I want to connect the UART3 to the virtual COM connector and use the UART2 for the Arduino connector (CN9 Pin 1 and 2),

The description is for an Nucleo-64 STM32L476, but should be compatible to some more Nucleo-64 boards, too.

Hardware changes

Switch UART2 to the Arduino connector

1. open solder bridge SB13 and SB14
2. close solder bridge SB62 and SB63

Nucleo-64 evaluation board

Switch UART3 to the VCOM of the ST-Link

1.  connect ST-Link connector TX to PC5 (Uart3 RX, CN10 pin 6)
2. connect ST-Link connector RX to PC4 (Uart3 TX, CN10 pin 34)

Software changes

• initialize UART3  (e.g. 115200 Baud, 8N1) with PC4 and PC5
• in case you want to use printf

int __io_putchar(int ch) {
    HAL_UART_Transmit(&huart3, (uint8_t *)&ch, 1, 0xFFFF);
    //ITM_SendChar(ch);
    return ch;
}

• alternatively overwrite _write()