Diff: main.cpp

Revision:

0:fe71c302ccbb

Child:

1:f4088d23f670

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Jul 09 09:16:31 2015 +0000
@@ -0,0 +1,74 @@
+/*   Interrupt, timer and ticker example on LPC1768 
+*
+*    @author: Baser Kandehir 
+*    @date: July 9, 2015
+*    @license: Use this code however you'd like
+*   
+*    @description of the program: 
+*
+*    This is an example program that shows how to use timer, ticker and interrupts. 
+*    It uses LPC1768 board leds and a button to show how interrupts, timers and tickers 
+*    are implemented to toggle leds. 
+*    A ticker is an interrupt service routine which calls a function at periodic time intervals.
+*    There are two tickers in the program. First ticker calls the toggle_led1 function every 100 ms
+*    and second ticker calls the toggle_led2 function every 500 ms. A button is connected to show
+*    how external interrupts work on the mbed LPC1768. Whenever user pushes the button, it pulls
+*    down the pin 18 to 0V and external interrupt occurs at the falling edge of p18. Whenever an external
+*    interrupt occurs, it calls the led3_debounced function to toggle led3. Also a timer is used to debounce 
+*    the button by counting 20 ms. Debounce is required for buttons in order to prevent false readings. 
+*     
+*    @connections: Pull up button with 10k resistor is connected to pin 18.   
+*     
+*/
+
+#include "mbed.h"
+
+Ticker toggler1;            // periodic interrupt routines
+Ticker toggler2;
+Timer debounce;             // define debounce timer
+InterruptIn button(p18);    // hardware interrupt on button - pin 18
+
+/* IMPORTANT NOTE: any digital input can be an interrupt except pin 19 and pin 20 */
+
+/* Interesting way of initialize all the 4 leds on the LPC1768 to an array named leds[]. */
+DigitalOut leds[] = {(LED1), (LED2), (LED3), (LED4)};
+
+/* Function Prototypes */
+void toggle_led1();
+void toggle_led2();
+void led3_debounced();
+
+int main() 
+{ 
+    /* Leds are initially OFF */
+    for(int i=0; i<4 ;i++)
+        leds[i]=0;            
+   
+    /* Start debounce timer */
+    debounce.start();
+    
+    /* Attach functions to periodic interrupts */
+    toggler1.attach(&toggle_led1,0.1);     // toggles led1 every 100 ms
+    toggler2.attach(&toggle_led2,0.5);     // toggles led2 every 500 ms
+    
+    /* Call toggle_led3 falling edge of the button interrupt */
+    button.fall(&led3_debounced);  
+    while(1) 
+    {
+            
+    }
+}
+
+void toggle_led1() {leds[0] = !leds[0];}
+void toggle_led2() {leds[1] = !leds[1];}
+
+// whenever user pushes the button, led3 toggles.
+// button is debounced by waiting at least 20 ms.
+void led3_debounced()
+{
+    if(debounce.read_ms()>20)      // only allow toggle after 20 ms
+    {
+        leds[2] = !leds[2];
+        debounce.reset();          // restart timer after toggle    
+    }         
+}