Is it possible to use USART RX/TX legs to blink a led?

[MSzal.1]

Hello!

I have an STM32F411RE nucleoboard.

I tried to use PA2 (TX) and PA3 (RX) as a general output. I enabled the clock access and also setted the mode register to general purpose output mode, but when I connect the LED and set the pin high nothing happens. If I connect it to another pins e.g. PA0 (A0), PA1 (A1), PA8 (D7) it works fine. Could it be because the RX/TX legs can't be used as a general purpose output?

Thanks in advance for the help!

Best regards,

Martin

[Mike_ST]

Hello,

PA2/PA3 can be used as GPIO, but you have to remove SB14 and SB13 to disconnect them from the ST-Link UART interface.

 + check that SB62 and SB63 are set.

[S.Ma]

MCU Tx is output and input on stlink side, so if you can't mingle the solder bridge, that shpuld work.Make sute to program the pin as output push pull.

[MSzal.1]

Sorry for this dumb question. Could You show me on the pictures which solder bridge should I remove? I checked the datasheet and I found SB13 and SB14 but I can't see where it joins. I attached 3 pictures about the board.

Thank You! 🙂

[Mike_ST]

I can't show you with your pictures, because it is on the other side of the board.

In UM1724 page 14 Figure 4 "Bottom layout", they are shown.

https://www.st.com/resource/en/user_manual/um1724-stm32-nucleo64-boards-mb1136-stmicroelectronics.pdf

[MSzal.1]

Yes I also found it. Maybe I misunderstood it. When you wrote that I had to remove SB13 and SB14, You meant that I had to remove the transistors from the board? I thought that I had to remove only a jumper.

[MSzal.1]

I checked the code it but still not works. The delay is from TIM2_CH1 (PA0). It1s interesting because it worked on PA1 and PA4.

[Mike_ST]

Solder Bridges 13 and 14 are 0 Ohm resistors.

They are not jumpers, so you'll have to use soldering iron.

[MSzal.1]

Okay, I understand now. 🙂 Thank you!

[Mike_ST · Accepted solution]

As I said before don't forget to close SB62 and SB63 too, just a bit of tin between the pads will do the job.