Revision 0:11cc29f22037, committed 2015-11-16

Comitter:

manitou

Date:

Mon Nov 16 16:56:32 2015 +0000

Commit message:

LPC1768 RTC freq check with WDT

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Mon Nov 16 16:56:32 2015 +0000
@@ -0,0 +1,57 @@
+// use WDT to measure drift of RTC and IRC
+// seems WDT ISR will only fire once
+#include "mbed.h"
+
+DigitalOut led1(LED1);
+uint32_t ticks;
+
+void kick() {
+    __disable_irq();
+    LPC_WDT->WDFEED = 0xAA;
+    LPC_WDT->WDFEED = 0x55;
+    __enable_irq();
+}
+
+void isr_wdt(void) {
+    ticks++;
+    led1 = 1;
+    LPC_WDT->WDMOD |= (1<<3);
+ //    LPC_WDT->WDMOD &= ~(1<<2);
+ //   kick();
+}
+
+void wdt_init() {
+    LPC_WDT->WDCLKSEL = 0x2;               // Set CLK src 0 IRC  1 PCLK   2 RTC
+   // uint32_t clk = SystemCoreClock / 16;    // WD has a fixed /4 prescaler, PCLK default is /4
+    LPC_WDT->WDTC = 0xfffffff;    // max countdown
+    LPC_WDT->WDMOD = 0x01;  // enable but no reset
+    NVIC_SetVector(WDT_IRQn, (uint32_t)&isr_wdt);
+    NVIC_ClearPendingIRQ(WDT_IRQn);
+    NVIC_EnableIRQ(WDT_IRQn);
+    kick();
+}
+
+int main() {
+    uint32_t t,t0=0,us,us0,prev;
+    int ppm;
+    Timer tmr;
+    tmr.start();
+    printf("hello %x\n",LPC_WDT->WDMOD);
+    wait(1.0);
+    wdt_init();
+    prev=LPC_WDT->WDTV;
+    while(1) {
+        t=LPC_WDT->WDTV;
+        us = tmr.read_us();
+        if (t0==0 || t0 == 255) {
+            t0 = t;
+            us0 = us;
+        }
+        double tf = (t0-t)/8192.;  //  /8192 for rtc   1000000 for IRC
+        double secs = 1.e-6*(us-us0);
+        ppm = 1.e6*(tf-secs)/secs;
+        printf("ticks %d %d %u %d us  %x %d ppm \n",ticks,prev-t,t0-t,us-us0,t,ppm);
+        prev=t;
+        wait(2.0);
+    }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Mon Nov 16 16:56:32 2015 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/da0ca467f8b5
\ No newline at end of file