main.cpp

00001 #include "mbed.h"
00002 DigitalOut internalLED(LED1);
00003 DigitalOut myled(p18);
00004 DigitalIn pb(p26);
00005 
00006 // LEDs used to indicate code activity and reset source
00007 DigitalOut myled1(LED1); //in main loop part 1
00008 DigitalOut myled2(LED2); //in main loop part 2 (where fault occurs)
00009 DigitalOut myled3(LED3); //The pushbutton or power on caused a reset
00010 DigitalOut myled4(LED4); //The watchdog timer caused a reset
00011 // SPST Pushbutton demo using internal PullUp function
00012 // no external PullUp resistor needed
00013 // Pushbutton from P8 to GND.
00014 
00015 class Watchdog {
00016 public:
00017 // Load timeout value in watchdog timer and enable
00018     void kick(float s) {
00019         LPC_WDT->WDCLKSEL = 0x1;                // Set CLK src to PCLK
00020         uint32_t clk = SystemCoreClock / 16;    // WD has a fixed /4 prescaler, PCLK default is /4
00021         LPC_WDT->WDTC = s * (float)clk;
00022         LPC_WDT->WDMOD = 0x3;                   // Enabled and Reset
00023         kick();
00024     }
00025 // "kick" or "feed" the dog - reset the watchdog timer
00026 // by writing this required bit pattern
00027     void kick() {
00028         LPC_WDT->WDFEED = 0xAA;
00029         LPC_WDT->WDFEED = 0x55;
00030     }
00031 };
00032  
00033 // Setup the watchdog timer
00034 Watchdog wdt;
00035 
00036 int main() {
00037     pb.mode(PullUp);
00038     int count = 0;
00039 // On reset, indicate a watchdog reset or a pushbutton reset on LED 4 or 3
00040     if ((LPC_WDT->WDMOD >> 2) & 1)
00041         myled4 = 1; else myled3 = 1;
00042         
00043 // setup a 10 second timeout on watchdog timer hardware
00044 // needs to be longer than worst case main loop exection time
00045     wdt.kick(10.0);  
00046  
00047 // Main program loop - resets watchdog once each loop iteration
00048 // Would typically have a lot of code in loop with many calls
00049     while (1) {
00050         myled1 = 1; //Flash LEDs 1 & 2 to indicate normal loop activity
00051         wait(.05);
00052         myled1 = 0;
00053         myled2 = 1;
00054         wait(.05);
00055 // Simulate a fault lock up with an infinite while loop, but only after 25 loop iterations
00056         if (count == 25) while (1) {};
00057 // LED 2 will stay on during the fault
00058         myled2 = 0;
00059         count ++;
00060 // End of main loop so "kick" to reset watchdog timer and avoid a reset
00061         wdt.kick();
00062        
00063         myled = !pb;
00064         internalLED = pb; 
00065     }
00066 }
00067