How to interrupt a Timer to Change position along a Colour Cycle

Question

I want to have a loop of 4 colours which runs constantly (i.e. red -> green -> blue -> white) each of the colours having their own LED and pin on the Arduino board. There is a 7 second delay between switching the colour and this cycle should run continuously. When I press a button, I want the cycle to immediately switch back to green and continue the cycle (i.e. -> blue -> white -> red) again.

How should I go about this? Can you have a listener for a button press going at the same time as a delay? How do you interrupt the timer and change the active LED?

Answer 1

You could start with the attachInterrupt example sketch and work from there. Here is a possible solution:

enum { GREEN = 0, BLUE = 1, WHITE = 2, RED = 3};
const int buttonPin = 2;
const int ledPin[] = { 4, 5, 6, 7 };
volatile bool reset = false;
int state = GREEN;
void setup() {
 pinMode(buttonPin, INPUT_PULLUP);
 for (int i = 0; i < 4; i++) pinMode(ledPin[i], OUTPUT);
 attachInterrupt(digitalPinToInterrupt(buttonPin), doResetState, FALLING);
}
void loop() {
 digitalWrite(ledPin[state], HIGH);
 delay(7000);
 digitalWrite(ledPin[state], LOW);
 if (state == RED || reset) {
 state = GREEN;
 reset = false;
 }
 else {
 state = state + 1;
 }
}
void doResetState () {
 reset = true;
}

This will not immediately cycle back to GREEN when pressing the button but you can fix that by modifying the doResetState().

Cheers!

Answer 2

The SimpleTimer library would be ideal for this. One timer callback function, the present contents of the loop() function, would advance the lighting state, called by a 7 second timer. Another, your present doResetState() with the modification noted by @MikaelPatel, would read (and debounce) the button on, say, a 100ms timer. The main loop would be reduced to Timer.run();