Indexing a constant from an array somehow does not "count" as constant

Projects Programming
1

Hi all,

I have a function:

void changeRecordgLED (int pinNumber, int state) {
  digitalWrite (pinNumber, state);
  switch (pinNumber) {
    case gLEDPin [0]:
      bitWrite (sensorActuatorStatusCurrent, 5, state);
      break;
    case gLEDPin [1]:
      bitWrite (sensorActuatorStatusCurrent, 6, state);
      break;
    case gLEDPin [2]:
      bitWrite (sensorActuatorStatusCurrent, 7, state);
      break;
  }
  sensorActuatorStatusPrior = sensorActuatorStatusCurrent;
}

and the relevant variable:

int gLEDPin [3] = {4, 9, 5};

And I get this error:
"the value of 'gLEDPin' is not usable in a constant expression"

I'm lost. I'd appreciate any help on this.

2

The index may be constant, but the array you're indexing into isn't.

3

Thank you for your reply.

Isn't, for example, gLED[0] a constant (4, in this case)?

4

But the compiler knows you can change that value at any time while the program is running.

This is your promise that you won't / can't do that:

const int gLEDPin [3] = {4, 9, 5};
5

Thank you!

Though I'm still getting the same error somehow.

6

Hard to know why without having a complete code to copy / paste into the Arduino and seeing the same error you are.

7

Got it. I've attached the full code (it was too long for copy and pasting).

V1.Scratch3.ino (18.3 KB)

variables.h (1.72 KB)

8

OK, go with:

constexpr int gLEDPin [3] = {4, 9, 5};

That tells the compiler it can calculate the values at compile-time.

BTW, 99.9% of that code was unrelated to your problem. That made it clutter that I had to remove because I don't have the required libraries installed.

Next time, post an MCVE

9

Thank you!

And thank you for the link!

The error is resolved now!