Time¶

Arduino provides four different time manipulation functions. They are

delay () function¶

The way the delay() function works is pretty simple. It accepts a single integer (or number) argument. This number represents the time (measured in milliseconds). The program should wait until moving on to the next line of code when it encounters this function. However, the problem is, the delay() function is not a good way to make your program wait, because it is known as a “blocking” function.

delay() function Syntax¶

delay (ms) ;

where, ms is the time in milliseconds to pause (unsigned long).

Example¶

/* Flashing LED
   * ------------
   * Turns on and off a light emitting diode(LED) connected to a digital
   * pin, in intervals of 2 seconds. *
*/

int ledPin = 13; // LED connected to digital pin 13

void setup() {
   pinMode(ledPin, OUTPUT); // sets the digital pin as output
}

void loop() {
   digitalWrite(ledPin, HIGH); // sets the LED on
   delay(1000); // waits for a second
   digitalWrite(ledPin, LOW); // sets the LED off
   delay(1000); // waits for a second
}

delayMicroseconds () function¶

The delayMicroseconds() function accepts a single integer (or number) argument. This number represents the time and is measured in microseconds. There are a thousand microseconds in a millisecond, and a million microseconds in a second.

Currently, the largest value that can produce an accurate delay is 16383. This may change in future Arduino releases. For delays longer than a few thousand microseconds, you should use the delay() function instead.

delayMicroseconds() function Syntax¶

delayMicroseconds (us) ;

where, us is the number of microseconds to pause (unsigned int)

Example¶

/* Flashing LED
   * ------------
   * Turns on and off a light emitting diode(LED) connected to a digital
   * pin, in intervals of 1 seconds. *
*/

int ledPin = 13; // LED connected to digital pin 13

void setup() {
   pinMode(ledPin, OUTPUT); // sets the digital pin as output
}

void loop() {
   digitalWrite(ledPin, HIGH); // sets the LED on
   delayMicroseconds(1000); // waits for a second
   digitalWrite(ledPin, LOW); // sets the LED off
   delayMicroseconds(1000); // waits for a second
}

millis () function¶

This function is used to return the number of milliseconds at the time, the Arduino board begins running the current program. This number overflows i.e. goes back to zero after approximately 50 days.

millis() function Syntax¶

millis () ;

This function returns milliseconds from the start of the program.

Example¶

unsigned long time; void setup() { 
   Serial.begin(9600); 
} 

void loop() { 
   Serial.print("Time:"); time = millis();
   //prints time since program started
   Serial.println(time); 
   // wait a second so as not to send massive amounts of data
   delay(1000); 
}

micros () function¶

The micros() function returns the number of microseconds from the time, the Arduino board begins running the current program. This number overflows i.e. goes back to zero after approximately 70 minutes. On 16 MHz Arduino boards (e.g. Duemilanove and Nano), this function has a resolution of four microseconds (i.e. the value returned is always a multiple of four). On 8 MHz Arduino boards (e.g. the LilyPad), this function has a resolution of eight microseconds.

micros() function Syntax¶

micros () ;

This function returns number of microseconds since the program started (unsigned long)

Example¶

unsigned long time; void setup() { 
   Serial.begin(9600); 
} 

void loop() { 
   Serial.print("Time:");
   time = micros(); //prints time since program started
   Serial.println(time); // wait a second so as not to send massive amounts of data
   delay(1000); 
}