Diff: main.cpp

Revision:

0:8ac51305f7f7

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Nov 28 15:10:54 2017 +0000
@@ -0,0 +1,57 @@
+#include "mbed.h"
+// LEDs used to indicate code activity and reset source
+DigitalOut myled1(LED1); //in main loop part 1
+DigitalOut myled2(LED2); //in main loop part 2 (where fault occurs)
+DigitalOut myled3(LED3); //The pushbutton or power on caused a reset
+DigitalOut myled4(LED4); //The watchdog timer caused a reset
+ 
+// Simon's Watchdog code from
+// http://mbed.org/forum/mbed/topic/508/
+class Watchdog {
+public:
+// Load timeout value in watchdog timer and enable
+    void kick(float s) {
+        LPC_WDT->WDCLKSEL = 0x1;                // Set CLK src to PCLK
+        uint32_t clk = SystemCoreClock / 16;    // WD has a fixed /4 prescaler, PCLK default is /4
+        LPC_WDT->WDTC = s * (float)clk;
+        LPC_WDT->WDMOD = 0x3;                   // Enabled and Reset
+        kick();
+    }
+// "kick" or "feed" the dog - reset the watchdog timer
+// by writing this required bit pattern
+    void kick() {
+        LPC_WDT->WDFEED = 0xAA;
+        LPC_WDT->WDFEED = 0x55;
+    }
+};
+ 
+// Setup the watchdog timer
+Watchdog wdt;
+ 
+int main() {
+    int count = 0;
+// On reset, indicate a watchdog reset or a pushbutton reset on LED 4 or 3
+    if ((LPC_WDT->WDMOD >> 2) & 1)
+        myled4 = 1; else myled3 = 1;
+        
+// setup a 10 second timeout on watchdog timer hardware
+// needs to be longer than worst case main loop exection time
+    wdt.kick(10.0);  
+ 
+// Main program loop - resets watchdog once each loop iteration
+// Would typically have a lot of code in loop with many calls
+    while (1) {
+        myled1 = 1; //Flash LEDs 1 & 2 to indicate normal loop activity
+        wait(.05);
+        myled1 = 0;
+        myled2 = 1;
+        wait(.05);
+// Simulate a fault lock up with an infinite while loop, but only after 25 loop iterations
+        if (count == 25) while (1) {};
+// LED 2 will stay on during the fault
+        myled2 = 0;
+        count ++;
+// End of main loop so "kick" to reset watchdog timer and avoid a reset
+        wdt.kick();
+    }
+}
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