/* * In these lessons, you are going to build a digital alarm clock. * The starting point for this goal is displaying the time * on the screen. */ //Include the Maker Screen library of code so that you can control it. #include "MakerScreenXVI.h" /* * A library is a collection of tools that are prepared in advance * to make programming easier. There are libraries that let you * interact with all kinds of sensors, actuators, and other * electronics. This one is for the MakerScreen 16x2 LCD screen */ /* * Once you have the library in the code, you need to be able to use * the resources it provides. To do that, create what's called * an Object. An object is a specific version of the kind of thing * a library describes. */ MakerScreenXVI lcd; //create an object named lcd for MakerScreenXVI /* * In this case, 'MakerScreenXVI' is the type of thing we're going * to use, and 'lcd' is the specific screen connected to our * hardware. In coding terms 'lcd' is an instance of 'MakerScreenXVI' */ // Create three variables for time: hours, minutes, and seconds int seconds = 20; int minutes = 40; int hours = 10; // Create a central 'timer' variable. It is a 'long' type. long timer; /* * This variable has a different 'type' from the other variables you * have seen, which were 'int's- it is a 'long'. Different variables * have different types so they can store different sorts of numbers. * 'long' means that it can store very big numbers, which is * important, because millis(), which you will use with timer, has * very large numbers as outputs */ /* * Arduino is designed with two specific places for code to run: * void setup() and void loop(). Everything bewtween the { and the } * of void setup() is run one time. It's where you put code that starts * devices or initializes settings. */ void setup() { lcd.begin(); //.begin() method sets the screen up to accept commands /* * Methods are how you use objects, they tell the instance to do * something. In this case, telling the object named lcd to * initialize itself and become ready to accept input. */ /* The backlightOn() method turns on the LED embedded in the screen. * Place two slashes (//) in front of this line to 'comment it out'. * Re-upload the code and see what it looks like without backlight. */ lcd.backlightOn(); /* * This next line is something new. What you do is take 'timer' and * set it to the value that millis() measures. Millis() is a * function in arduino that tells you how many milliseconds * have passed since the board was powered on. Set timer equal to it * so you can measure the difference between millis() now and later. */ timer = millis(); } /* * After setup() is loop(). Code written between the { and } of * void loop() executes over and over as long as the Maker Board is * powered on. Most code you write will be in loop, as you usually want * continuous operation. Loop can run millions of times per second! */ void loop() { /* * This next bit of code is another new one. It is what is called * an 'if' block. What it does is check the expression contained * in the parentheses after 'if' and finds out if it is true. In * the below, the check is whether millis(), the current time in * milliseconds since the board started, minus timer, the time * when you last set that variable, is greater than 1000. Then, * the code contained within the {} is executed only if the * check was true. */ if (millis() - timer >= 1000){ // If the time since the last check was more than a second, // increase 'seconds' seconds = seconds + 1; // Reset the timer, to keep track of when the last // second was added timer = millis(); } /* * The above chunk of code forms the basis of othe whole clock, by * keeping track of seconds at the real time level. */ /* * Next, check if enough seconds have passed that can mark * a whole minute gone by. The >= symbol says to do what is in the * {} if seconds is at or past 60. */ if (seconds >= 60){ /* * If so, take off a minute's worth of seconds. You do this * this way incase extra time has passed (if there are 61 * seconds, don't want to throw away that extra second!) */ seconds = seconds - 60; minutes = minutes + 1; } // Do the same sort of thing for minutes and hours that // you did for seconds and minutes: if (minutes >= 60){ minutes = minutes - 60; // Reduce 'minutes' by 60 hours = hours + 1; // Increase hours by 1 } /* * Once you've taken care of counting hours, minutes, and seconds, * you can put them on the display. */ lcd.clear(); //Clear the display of previous information lcd.print(hours); //write the value of the 'hours' variable lcd.print(":"); //insert a colon // For minutes less than 10, you want to show a 0 before the actual // number, so use another if statement if (minutes < 10){ lcd.print("0"); } lcd.print(minutes);//print the value of the 'minutes' variable lcd.print(":"); // Print the seconds. Second should include leading 0s like minutes if (seconds < 10){ lcd.print("0"); } lcd.print(seconds);//print the value of the 'seconds' variable /* * Then, once all that is on the screen, put in a short delay. * You do this because the loop() code executes as fast as possible, * so clearing and re-writing the time would look very flickery * without a little time for the display to stay on */ delay(300); // 300 ms is 30% of a second, so it won't interfere with the // clock, since the minimum check you make is for 1000 ms } /* * You saw many new things in this lesson: * new variable types so that you can use millis(), and * millis() itself! You learned about using 'if' * statements to make checks and run specific code under certain * circumstances, and about how the conditional statements used in * if blocks work. * * This project looks like a very basic clock with its segments of * seconds, minutes, and hours, but it's really a timer measuring its * own run time. * * In the next lesson, you will alter this code so that it * tracks hours properly like a clock, cycling through the 12 hour * cycle with AM/PM. */ // (c) 2017 Let's Start Coding. License: www.letsstartcoding.com/bsdlicense