Cristian Fuentes

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9 years ago.

what happen with PA2 and PA3?

Hello. I am a super beginner in mbed and I hope somebody can help me.

I wrote a program to count with a 7seg. this is the program

#include "mbed.h"

#define IOS (0xA0) // PA_5 + PA_7
 
#define MASK (0xFF) // Pins 0,1,2,3,4,5,6,7 
 
PortOut myIOs(PortA, MASK); 
//PortOut my7Seg(PortA,MASK); 

//values of the LEDs
int leds[10]={
     0b11000000,
     0b11111001,
     0b10100100,
     0b10110000,
     0b10011001,
     0b10010010,
     0b10000010,
     0b11011000,
     0b10000000,
     0b10010000
 };

 
int main()
{
   while(1){
    for(int i=0;i<10;i++){
        // myIOs=leds[i];//0;
         //myIOs=0b01111111;
         myIOs=0b00000000;
       //my7seg=leds[i];
       //my7Seg  
       wait(0.5); // 500 ms       
      }//for
    }//while
 }

for some reason all Port A pins work except PA2 and PA3.(Now i am turning on ALL pins PA0PA7 but they dont work) And I cant find why. Can someone tell me if there is something special about these pins and how to solve this problem.

Question relating to:

Last updated: 30 Apr 2020

One year later I can comment on this. PA2 and PA3 are not connected. Also PA13 ans PA14 are not recommended to use. And PC14 and PC15 also have some issues.

posted by Cristian Fuentes 27 Apr 2017

1 Answer

Erik -
9 years ago.

It is handy to mention the board you have. PA2 and PA3 are also the pins used for connecting via the USB Serial, and the pins on the board are by default not connected. If you want to use them anyway you need to place a jumper somewhere, the Nucleo user guide should mention it if I am correct.

Accepted Answer

Thanks for the answer. I am using the F091RC. After searching for an answer in the docs, finally I got something similar to what you said but not with USB but with USART. It seems they are disconnected and that depends on jumpers SB62 SB63 SB13 and SB14.

Are there any other pins with this "special" behavior that I should be aware of?

Thanks again , very much appreciated

posted by Cristian Fuentes 16 Dec 2015

Yeah it is the USART connected to the USB interface (via the ST-link part). I don't think there are others with issues like this. It is because for some reason they wanted to copy Arduino too much, it makes little sense tbh.

posted by Erik - 16 Dec 2015