Serial receive

Receive a single char to trigger anything.

Enable the USART:

1. The STM32 Nucleo boards are connected to computer via USART2. To enable it, set PA3 to alternate function USART2_RX.
2. Enable UART2 in APB1ENR.
3. After setting the baudrate enable USART with UE bit and receiver with RE bits.

Set the baudrate:

To set the baudrate we need to calculate the equation: APB1_CLK+(BAUDRATE/2U) / BAUDRATE and place it into USART2->BRR register.

Read a single char:

I wrote a simple rx_read function which listens for incoming data and returns the buffer from data register.

You can see the LED turning on when writing "A" char via serial port, and turning off when "B" is received. This example is not convenient as it blocks the execution of code. In the next example I will use interrupt to create a non-blocking receiver.

To work with Serial monitor you can open Arduino IDE Serial Monitor or install other software.