Remember the Mode

Part of the Timing Without Delay section of Coddy's Arduino journey. Lesson 7 of 18.

A button press lasts a fraction of a second, but what it starts can last much longer. To carry on after the button is let go, the sketch has to remember what it is doing. A variable for that is called a state or a mode:

int mode = 0;   // 0 = off, 1 = blinking

Split loop() in two. First, the inputs only change the mode. Then, the rest of the loop does what the mode says:

// 1. inputs change the mode
if (digitalRead(blinkButton) == LOW) {
  mode = 1;
}

// 2. the mode decides what happens
if (mode == 1) {
  // blink with millis()
} else {
  digitalWrite(ledPin, LOW);
}

Each number stands for one thing the sketch can be doing. Write what each number means in a comment. A sketch can have as many modes as it needs: 0, 1, 2, 3 and more.

Challenge

Easy

The green button is on pin 2 and the red one on pin 3.

green sets mode to 1, red sets it to 0
when mode is 1, the LED on pin 13 blinks with millis(), 500 ms on and 500 ms off
when mode is 0, the LED is off

Press Run, press green, let go, then press red. Then Check.

Try it yourself

const int ledPin = 13;
const int blinkButton = 2;   // green
const int offButton = 3;     // red

int mode = 0;   // 0 = off, 1 = blinking

unsigned long previousMillis = 0;
int ledState = LOW;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(blinkButton, INPUT_PULLUP);
  pinMode(offButton, INPUT_PULLUP);
}

void loop() {
  // 1. the buttons only change mode

  // 2. then do what the mode says
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Timing Without Delay

1millis()

The millis() Clock Times in unsigned long Blink Without Delay Two LEDs, Two Speeds Blink While a Button Toggles A Light on a Timer

4Precise Timing

Measure With micros()When millis() Rolls Over Button Stopwatch

2State Machines

Remember the ModeChoosing With switch Named States With enum Traffic Light State Machine Cycle Modes With a Button

3Interrupts

A Press the Loop Misses FALLING, RISING and CHANGE Sharing With volatile Count Presses by Interrupt

Practice on your own: Arduino playground