Time Check

This example for a Yún device gets the time from the Linux processor via Bridge, then parses out hours, minutes and seconds for the Arduino. The Yún device must be connected to a network to get the correct time. If you used the web-based WiFi interface to configure the Yún device for the network, make sure you've selected the proper time zone.

Hardware Required

Yún board or shield
WiFi network connected to the internet

Circuit

There is no circuit for this example.

Yun Fritzing

image developed using Fritzing. For more circuit examples, see the Fritzing project page

Code

You need to include the Process class : #include <Process.h>

Create an instance of Process that will be used to get the date, and create variables to hold the current hour, minute, and second. You'll also want to create a variable to store the previous time. To start, put in a value that cannot be a valid time (like a negative number).

Process date;
int hours, minutes, seconds;
int lastSecond = -1;

In @@setup()@ initialize Bridge and Serial. Wait until there is a serial connection before continuing with the sketch and printing a status to the serial monitor.

void setup() {

  Bridge.begin();

  Serial.begin(9600);

  while(!Serial);

  Serial.println("Time Check");

Run an initial process to get the time by adding the parameter "T" to date.

if (!date.running())  {

    date.begin("date");

    date.addParameter("+%T");

    date.run();

  }
}

In loop() check to see if a second has passed since the previous time. If so, print out the current time to the serial monitor and restart the date process if it has stopped.

void loop() {

  if(lastSecond != seconds) {  // if a second has passed

    if (hours <= 9) Serial.print("0");    // adjust for 0-9

    Serial.print(hours);

    Serial.print(":");

    if (minutes <= 9) Serial.print("0");  // adjust for 0-9

    Serial.print(minutes);

    Serial.print(":");

    if (seconds <= 9) Serial.print("0");  // adjust for 0-9

    Serial.println(seconds);

    if (!date.running())  {

      date.begin("date");

      date.addParameter("+%T");

      date.run();

    }

  }

If there is a result from the date process, parse the data. First, store the result (hh:mm:ss) in a string, then find the location of the colons with indexOf() and lastIndexOf().

while (date.available()>0) {

    String timeString = date.readString();

    int firstColon = timeString.indexOf(":");

    int secondColon= timeString.lastIndexOf(":");

Knowing the index numbers of the colons, you can separate the hours minutes and seconds as substrings :

String hourString = timeString.substring(0, firstColon);

    String minString = timeString.substring(firstColon+1, secondColon);

    String secString = timeString.substring(secondColon+1);

Finally, convert the strings to ints, and save the previous second to do a time comparison in the next loop().

hours = hourString.toInt();

    minutes = minString.toInt();

    lastSecond = seconds;

    seconds = secString.toInt();

  }
}

The complete code follows :


/*

  Time Check

 Gets the time from Linux via Bridge then parses out hours,

 minutes and seconds using a YunShield/Yún.

 created  27 May 2013

 modified 21 June 2013

 By Tom Igoe

 This example code is in the public domain.

 http://www.arduino.cc/en/Tutorial/TimeCheck

 */

#include <Process.h>

Process date;                 // process used to get the date
int hours, minutes, seconds;  // for the results
int lastSecond = -1;          // need an impossible value for comparison

void setup() {

  Bridge.begin();        // initialize Bridge

  SerialUSB.begin(9600);    // initialize serial

  while (!Serial);              // wait for Serial Monitor to open

  SerialUSB.println("Time Check");  // Title of sketch

  // run an initial date process. Should return:

  // hh:mm:ss :

  if (!date.running()) {

    date.begin("date");

    date.addParameter("+%T");

    date.run();

  }
}

void loop() {

  if (lastSecond != seconds) { // if a second has passed

    // print the time:

    if (hours <= 9) {

      SerialUSB.print("0");  // adjust for 0-9

    }

    SerialUSB.print(hours);

    SerialUSB.print(":");

    if (minutes <= 9) {

      SerialUSB.print("0");  // adjust for 0-9

    }

    SerialUSB.print(minutes);

    SerialUSB.print(":");

    if (seconds <= 9) {

      SerialUSB.print("0");  // adjust for 0-9

    }

    SerialUSB.println(seconds);

    // restart the date process:

    if (!date.running()) {

      date.begin("date");

      date.addParameter("+%T");

      date.run();

    }

  }

  //if there's a result from the date process, parse it:

  while (date.available() > 0) {

    // get the result of the date process (should be hh:mm:ss):

    String timeString = date.readString();

    // find the colons:

    int firstColon = timeString.indexOf(":");

    int secondColon = timeString.lastIndexOf(":");

    // get the substrings for hour, minute second:

    String hourString = timeString.substring(0, firstColon);

    String minString = timeString.substring(firstColon + 1, secondColon);

    String secString = timeString.substring(secondColon + 1);

    // convert to ints,saving the previous second:

    hours = hourString.toInt();

    minutes = minString.toInt();

    lastSecond = seconds;          // save to do a time comparison

    seconds = secString.toInt();

  }

}

Table of Contents

Time Check

Hardware Required

Circuit

Code

See Also