swpol.hpp

00001 #include "mbed.h"
00002 
00003 class SWPoll {
00004     private:
00005     enum State {LOW, LOW_DEBOUNCE, HIGH,HIGH_DEBOUNCE};
00006     State state;
00007     DigitalIn& sw;
00008     DigitalOut& led;
00009     Timer t; 
00010 
00011     public:
00012     //Constructor
00013     SWPoll(DigitalIn& gpioIn,DigitalOut& gpioOut) : sw(gpioIn),led(gpioOut)
00014     {
00015         state = LOW;
00016         t.reset();
00017         led = 0;
00018     }
00019     //Deconstructor
00020     ~SWPoll(){
00021         //Shut Down
00022         t.stop();
00023         t.reset();
00024         led = 0;
00025     }
00026     // API - poll the switches
00027     // Use of a Timer to manage switch bounce
00028     void poll(){
00029         switch (state)
00030         {
00031         // waiting for switch to rise
00032         case LOW:
00033             if (sw == 1){
00034                 state = LOW_DEBOUNCE;
00035                 t.reset();
00036                 t.start();
00037             }
00038             break;
00039         case LOW_DEBOUNCE:
00040             if (t.read_ms() >= 200){
00041                 state = HIGH;
00042                 t.stop();
00043                 t.reset();
00044             }
00045             break;
00046         case HIGH:
00047             if (sw == 0) {
00048                 led = !led;
00049                 state = HIGH_DEBOUNCE;
00050                 t.reset();
00051                 t.start();
00052             }
00053             break;
00054         case HIGH_DEBOUNCE:
00055             if (t.read_ms() >= 200) {
00056                 state = LOW;
00057                 t.stop();
00058                 t.reset();
00059             }
00060             break;
00061         default:
00062             t.stop();
00063             t.reset();
00064             state = LOW;
00065             break;
00066         } //end switch
00067         //This is a Mealy Machine - so no output logic follows
00068                 
00069     }   
00070 };