main.cpp

00001 /*   Interrupt, timer and ticker example on LPC1768 
00002 *
00003 *    @author: Baser Kandehir 
00004 *    @date: July 9, 2015
00005 *    @license: MIT license
00006 *     
00007 *   Copyright (c) 2015, Baser Kandehir, baser.kandehir@ieee.metu.edu.tr
00008 *
00009 *   Permission is hereby granted, free of charge, to any person obtaining a copy
00010 *   of this software and associated documentation files (the "Software"), to deal
00011 *   in the Software without restriction, including without limitation the rights
00012 *   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
00013 *   copies of the Software, and to permit persons to whom the Software is
00014 *   furnished to do so, subject to the following conditions:
00015 *
00016 *   The above copyright notice and this permission notice shall be included in
00017 *   all copies or substantial portions of the Software.
00018 *
00019 *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
00020 *   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
00021 *   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
00022 *   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
00023 *   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00024 *   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
00025 *   THE SOFTWARE.
00026 *
00027 *    @description of the program: 
00028 *
00029 *    This is an example program that shows how to use timer, ticker and interrupts. 
00030 *    It uses LPC1768 board leds and a button to show how interrupts, timers and tickers 
00031 *    are implemented to toggle leds. 
00032 *    A ticker is an interrupt service routine which calls a function at periodic time intervals.
00033 *    There are two tickers in the program. First ticker calls the toggle_led1 function every 100 ms
00034 *    and second ticker calls the toggle_led2 function every 500 ms. A button is connected to show
00035 *    how external interrupts work on the mbed LPC1768. Whenever user pushes the button, it pulls
00036 *    down the pin 18 to 0V and external interrupt occurs at the falling edge of p18. Whenever an external
00037 *    interrupt occurs, it calls the led3_debounced function to toggle led3. Also a timer is used to debounce 
00038 *    the button by counting 20 ms. Debounce is required for buttons in order to prevent false readings. 
00039 *     
00040 *    @connections: Pull up button with 10k resistor is connected to pin 18.   
00041 *     
00042 */
00043 
00044 #include "mbed.h"
00045 
00046 Ticker toggler1;            // periodic interrupt routines
00047 Ticker toggler2;
00048 Timer debounce;             // define debounce timer
00049 InterruptIn button(p18);    // hardware interrupt on button - pin 18
00050 
00051 /* IMPORTANT NOTE: any digital input can be an interrupt except pin 19 and pin 20 */
00052 
00053 /* Interesting way of initialize all the 4 leds on the LPC1768 to an array named leds[]. */
00054 DigitalOut leds[] = {(LED1), (LED2), (LED3), (LED4)};
00055 
00056 /* Function Prototypes */
00057 void toggle_led1();
00058 void toggle_led2();
00059 void led3_debounced();
00060 
00061 int main() 
00062 { 
00063     /* Leds are initially OFF */
00064     for(int i=0; i<4 ;i++)
00065         leds[i]=0;            
00066    
00067     /* Start debounce timer */
00068     debounce.start();
00069     
00070     /* Attach functions to periodic interrupts */
00071     toggler1.attach(&toggle_led1,0.1);     // toggles led1 every 100 ms
00072     toggler2.attach(&toggle_led2,0.5);     // toggles led2 every 500 ms
00073     
00074     /* Call toggle_led3 falling edge of the button interrupt */
00075     button.fall(&led3_debounced);  
00076     while(1) 
00077     {
00078             
00079     }
00080 }
00081 
00082 void toggle_led1() {leds[0] = !leds[0];}
00083 void toggle_led2() {leds[1] = !leds[1];}
00084 
00085 // whenever user pushes the button, led3 toggles.
00086 // button is debounced by waiting at least 20 ms.
00087 void led3_debounced()
00088 {
00089     if(debounce.read_ms()>20)      // only allow toggle after 20 ms
00090     {
00091         leds[2] = !leds[2];
00092         debounce.reset();          // restart timer after toggle    
00093     }         
00094 }