Thatcher Chamberlin
The common example for running a watchdog timer on mbed processors doesn't work for the LPC1114, a common and easily-breadboardable ARM chip. My program provides a watchdog class that works on the LPC1114 but which is also similar to the common example found in https://mbed.org/forum/mbed/topic/508/
Diff: main.cpp
- Revision:
- 0:1c1e04c41063
diff -r 000000000000 -r 1c1e04c41063 main.cpp
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp Sun Aug 10 02:58:11 2014 +0000
@@ -0,0 +1,68 @@
+#include "mbed.h"
+
+/*
+Main code copied from: http://mbed.org/cookbook/WatchDog-Timer
+Modified for use with LPC1114 with source code found here:
+https://github.com/mbedmicro/mbed/blob/master/libraries/mbed/targets/cmsis/TARGET_NXP/TARGET_LPC11XX_11CXX/LPC11xx.h
+With some inspiration from:
+https://github.com/Mrjohns42/RSL/blob/master/LPC1114/nRF24L01/wdt.c
+*/
+
+// LEDs used to indicate code activity and reset source
+DigitalOut led1(dp1);
+DigitalOut led2(dp4);
+
+// 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_SYSCON->SYSAHBCLKCTRL = LPC_SYSCON->SYSAHBCLKCTRL|(1<<15);
+ LPC_SYSCON->WDTCLKSEL = 0x1; // Set CLK src to Main Clock
+ LPC_SYSCON->WDTCLKUEN = 0x01; /* Update clock */
+ LPC_SYSCON->WDTCLKUEN = 0x00; /* Toggle update register once */
+ LPC_SYSCON->WDTCLKUEN = 0x01;
+ LPC_SYSCON->WDTCLKDIV = 0x10;
+ uint32_t clk = SystemCoreClock/16; // WD has a fixed /4 prescaler, PCLK default is /4
+ LPC_WDT->TC = s * (float)clk;
+ LPC_WDT->MOD = 0x3; // Enabled and Reset
+ kick();
+ }
+// "kick" or "feed" the dog - reset the watchdog timer
+// by writing this required bit pattern
+ void kick() {
+ LPC_WDT->FEED = 0xAA;
+ LPC_WDT->FEED = 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->MOD >> 2) & 1)
+ led1 = 1; else led1 = 0;
+
+ // 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) {
+ wait(.1);
+ led2 = 1;
+ wait(.1);
+ // 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
+ led2 = 0;
+ count ++;
+ // End of main loop so "kick" to reset watchdog timer and avoid a reset
+ wdt.kick();
+ }
+}
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