PA4 and PA5 don't work STM8S208RB

[MykolaLevun]

Hello,

STM8S208RB microcontroller. Pins PA4 and PA5 do not work in push-pull mode. Why? I haven't tried it in other modes. It's not a microcontroller issue because I tested it on two different microcontrollers. Pins are shown in the datasheet (see figure bellow).

I tested the robotic functionality using this code:
main()
{
    PA_DDR = 0b01111110;
    PA_CR1 = 0b01111110;
    PA_CR2 = 0b00000000;
    PA_ODR = 0b00000000;
    while (1)
    {
        delay_miles(2000);
        PA_ODR = 0b01111110;
        delay_miles(2000);
        PA_ODR = 0b00000000;
    }
}

[AA1]

The problem is only with PA4 and PA5?

Try with other pins.

PA4 and PA5 are UART1 RX and TX pins. If UART1 is enable it controls these pins.

[MykolaLevun]

Works well with other pins. As far as I understand, after the reset the UART1 is turned off, but I didn’t turn it on in software. PA4 and PA5 are always logically 0, checked with an oscilloscope.

[AA1]

Maybe bootloader is active and it left UART1 enable. Check UART1 registers or disable UART1.

[MykolaLevun]

I checked it in the debugger and UART1 is turned off. I also need to say that I am using a NUCLEO-8S208RB board.

[MykolaLevun · Accepted solution]

The answer to why PA4 and PA5 did not work is in the UM2364 manual in section 6.8 USART communication

 (see figure below).