Populating an array on setup

Projects Programming
1

I'm working on a project and I'd like to populate an array on setup instead of in the main loop but I can't seem to get it to work and I'm not sure why. Below is the very basic example of my code. You can see that I have a call for a function in the setup but when printed out my array is nothing but zeros. If I call that same function in the main loop it works as expected.

uint8_t myArray[10][3];

void setup() {
  Serial.begin(115200);
  // put your setup code here, to run once:
  Fill();
}

void loop() {
  // put your main code here, to run repeatedly:
  //Fill();
  Serial.print(myArray[0][0]);
  Serial.print(", ");
  Serial.print(myArray[0][1]);
  Serial.print(", ");
  Serial.println(myArray[0][2]);
}


void Fill(){
  for (int i; i < 3; i++){
    myArray[0][i] = i;
  } 
}
2

Turn up the level of warnings in preferences.

You'll get some complaints from the compiler about this:

  for (int i; i < 3; i++){

Better:

  for (int i=0; i < 3; i++){
3

Ok... I guess I'm a little confused on why this works lol. By setting i equal to zero fixed the issue. Care to explain?

Thanks for the solution by the way.

4

If you don't set it to zero then what will its initial value be ?

As it is a local variable it could be anything (unlike a global which would be set to zero). If its initial value is 3 or more then the for loop will not run and the values in the array will be left at zero from when when it was declared as a global variable

5

I'm sure this is a good habit to get used to but I'm confused on why not setting i to 0 in the mail loop assumes as such but not in the setup. I will be sure to get in the habit no matter what though.

7

Delta_G:
It only worked in setup by accident.

For local variables if you don't give it a value then it gets whatever junk is left over in memory when it is created. When you did it in setup maybe that happened to be a 0. You got lucky.

I guess that make since.

Thank you!