Measure With micros()

Part of the Timing Without Delay section of Coddy's Arduino journey. Lesson 16 of 18.

millis() counts whole milliseconds, which is too coarse for short things: a 2.5 ms press would read as 2 or 3. micros() is the same kind of clock, but it counts microseconds, millionths of a second: 1000 of them in each millisecond.

On the Uno it goes up in steps of 4 microseconds, and it returns an unsigned long too. To time something, read it before and after, and subtract:

unsigned long start = micros();
int reading = analogRead(A0);
unsigned long took = micros() - start;
Serial.println(took);   // about 110: an analogRead() takes about 0.1 ms

Because it counts so fast, micros() runs out of numbers much sooner than millis(): after about 70 minutes it starts again from 0. Use it for short times, and millis() for anything longer than a few minutes.

Challenge

Easy

Measure how long the button is held, in microseconds:

when the button goes down, store micros() in pressedAt
when it comes up, print micros() - pressedAt

Press Run, tap the button, then Check.

Try it yourself

const int buttonPin = 2;

bool wasPressed = false;
unsigned long pressedAt = 0;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  Serial.begin(9600);
}

void loop() {
  bool pressed = digitalRead(buttonPin) == LOW;

  if (pressed && !wasPressed) {
    // the button just went down: remember the time
  }

  if (!pressed && wasPressed) {
    // the button just came up: print how long it was held, in microseconds
  }

  wasPressed = pressed;
}

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 Mode Choosing 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