Can't manage to get Pro Micro pins A0-A2 to act as digital outputs!?

Other Hardware 3rd Party Boards
1

Hi

I am trying to use the A0-A2 pins on an Arduino Pro Micro as digital outputs.

But no matter what I try, it doesn't work.

They are all just high level.

Here's a piece of code I tried.

#define CS A0
#define DC A1
#define RST A2


void toggleios(void)
{

  digitalWrite(CS,1);
  digitalWrite(DC,1);
  digitalWrite(RST,1);
  digitalWrite(16,1);
  delay(100);
  digitalWrite(CS,0);
  digitalWrite(DC,0);
  digitalWrite(RST,0);
  digitalWrite(16,0);
  delay(100);
}
void setup() {
  pinMode(CS,OUTPUT);
  pinMode(DC,OUTPUT);
  pinMode(RST,OUTPUT);
  pinMode(16,OUTPUT);
}

void loop() {
toggleios();
}

I have also tried using 18, 19 and 20 instead of A0, A1 and A2, same result.
What am I doing wrong or missing?
How do I get these pins to acts as digital outputs?

Another strange thing is that when I run this code, pin 15 will toggle simultaneously with pin 16.

2

According to this Pro Micro pinout, analog pins A0, A1 and A2 are addressed as digital pins using Arduino pin numbers 18, 19 and 20.

3

Yes, I tried that too, same result.

I added that to the original post now for clarification. Thanks for pointing it out.

4

Maybe it's not good with 1,0 as output states.
Have you tried using LOW, HIGH ?

5

I did not see pinMode() in your code, that is needed so the pins get initialized to the correct mode.

6

It's right there in setup :wink:

7

1 and 0 works fine, I have pin 16 as reference in the code and it works fine.

On the other hand I have tried some other code that used HIGH and LOW instead, same result.

8

You're here saying they "don't work", now they do?

9

How are you measuring that?

10

I just put a Pro Micro on a breadboard with your sketch and I'm not seeing anything unusual. LEDs on A0, A1, A2 and pin 16 are flashing, and the LED on pin 15 stays off.

11

With an oscilloscope and a logic analyzer.

12

Please don't modify your original post. It makes the thread difficult to follow.

13

@van_der_decken

So my Pro micro is not fully functional then. Too bad, it's new.

Thanks for helping out with this!

14

This is what I saw (and expected to):

off
on

Left to right: A2, A1, A0, 15, 16.

15

I happened to have two of these boards, so I tried the other one, also brand new, it's exactly the same with that one.

The both looks exactly like your board @van_der_decken , the pcb routing looks the same too.

I guess the conclusion has to be that I have gotten two bad boards.

16

Do the 'pins' in question work as Inputs (digital or analog) ?

17

Taking a deeper dive into the 32U4 datasheet I notice that the problematic pins are also used for the JTAG interface, and if this is enabled, these pin won't work as digital outputs. I have a hunch the JTAG interface is enabled on my devices.

It seems I must use an AVR ISP programmer to fix that. I will see if I can manage that.

18

This is the best AVR ISP programmer I've ever used, which also doubles as a USB-serial converter. Comes with a nice GUI that allows you to control various options, and works well with both 5V and 3.3V MCUs.

19

YES YES YES!

Lucky me I had an old Atmel-ICE tucked away in a drawer. Worked perfectly to connect to the Pro Micro JTAG interface.

Sure JTAG was enabled. So I disabled it, and now the IO's works as expected!

Thanks everyone for your efforts in helping me! It's highly appreciated!