How to execute a function just once in the void loop? - arduino

Question

Simply, I want to make a counter to execute a subroutine if digital read gets a toggle value just thefirst time. But the result shows that the "aFunction" executes more than once (repeatedly).
Code:
int lastState = 1;
void setup() {
Serial.begin(115200);
}
void loop() {
int currentState = digitalRead(D5);
if (currentState == 1) {
if (currentState = !lastState) {
aFunction();
}
lastState = !lastState;
}
Serial.println("Still running loop");
delay(2000);
}
void aFunction() {
Serial.println("in a function");
}

Answer 1

This is the final result:
bool executed = false;
void setup()
{
Serial.begin(115200);
}
void loop()
{
int currentState = digitalRead(D5);
if (currentState == 1 && executed == false)
{
aFunction();
executed = true;
}
if (currentState == 0 && executed == true)
{
aFunction();
executed = false;
}
Serial.println("Still running loop");
delay(2000);
}
void aFunction()
{
Serial.println("in a function");
}

Answer 2

By keeping track of execution of function and checking it along with currentState variable will help you in achieving your goal.
Your code with this change will look like:
bool executed = false;
void setup() {
Serial.begin(115200);
}
void loop() {
int currentState = digitalRead(D5);
if (currentState == 1 && executed == false) {
executed = true;
aFunction();
}
Serial.println("Still running loop");
delay(2000);
}
void aFunction() {
Serial.println("in a function");
}

Answer 3

You need a variable to signal it's been run once:
int lastState = 1;
int runOnce = 0;
void setup() {
Serial.begin(115200);
}
void loop() {
int currentState = digitalRead(D5);
if (currentState == 1) {
if (currentState = !lastState) {
if (runOnce == 0)
aFunction();
}
lastState = !lastState;
}
Serial.println("Still running loop");
delay(2000);
}
void aFunction() {
Serial.println("in a function");
runOnce = 1;
}
So now your aFunction() sets the runOnce flag to 1 and it won't ever run again until the device is reset due to the if statement inside loop().

Answer 4

Your problem lies right here:
if (currentState == 1) {
if (currentState = !lastState) {
aFunction();
}
lastState = !lastState;
}
This will run indefinitely until currentState /= 1. You are having problems because you're not exactly understanding how the code runs in runtime. The computer is reading this repeatedly, and its reading if currentState==1 to execute the bracket.
The next issue is your nested if statement, it's not using a comparison operator. You have an = sign, but you should have an == operator to compare currentstate to laststate.
Essentially, if you want it to run once, you need to make sure the function changes the variable currentState to something other than 1, then if you want this function to execute again at some other point during runtime, change currentState back 1 for this function to run again, where again it'll change currentState to something other than 1.
I suggest instead of using an integer for currentState to use a boolean true or false. If true, execute, change to false at the end - since its changed to false it wont run again until its true again.