I have a Nucleo F446RE, which writes to UART which is handled by the built-in ST-Link over VCP on USB.
I'd like to be able to see the serial signals on my oscilloscope as well. There are two exposed connectors, labelled TX and RX, which seem to connect to the USART2 (the same one connected to ST-Link). However, I see no signal on them on my scope.
Looking at the Nucleo data sheet:
6.8 USART communication
The USART2 interface available on PA2 and PA3 of the STM32 microcontroller can be connected to ST-LINK MCU, ST morpho connector, or to ARDUINO® connector. The choice can be changed by setting the related solder bridges. By default, the USART2 communication between the target STM32 and ST-LINK MCU is enabled, in order to support virtual COM port for Mbed™ (SB13 and SB14 ON, SB62 and SB63 OFF). If the communication between the target STM32 PA2 (D1) or PA3 (D0) and shield or extension board is required, SB62 and SB63 must be ON, while SB13 and SB14 must be OFF. In such a case, it is possible to connect another USART to ST-LINK MCU using flying wires between the ST morpho connector and CN3
I'm having trouble deciphering that, but it sounds like the USART is connected to either the ST-Link or the connector, not both, and that changing that requires soldering the board. Is that correct?
Is there anyway, without resoldering the Nucleo, to see a USART signal on an exposed pin or connector? I don't necessarily need USART2 - any one will do.