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?

1 Like
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.

1 Like
11

With an oscilloscope and a logic analyzer.

12

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

1 Like
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.

1 Like
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!

20

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