WDT not firing

[Lee Daniel Crocker]

This is SDK 8.1.0, Softdevice 7.3.0 (not being used for this demo), running on a NRF51822-CEAA.

The minimal program below just sets the WDT for 10 seconds, then goes into a loop showing a 1-second heartbeat so I can count. There's no timer or anything else feeding the dog, so it should (?) reset every 10 seconds. But it never does (I would see the different startup LED pattern). Is the interrupt getting disabled somehow? Yes, I changed WDT_ENABLED=1 in the header.

 #include <stdbool.h>
 #include <stdint.h>
 #include "nrf.h"
 #include "app_timer.h"
 #include "app_util_platform.h"
 #include "app_error.h"
 #include "nrf_drv_wdt.h"
 #include "debug.h"      // led_on(), app_error_handler(), etc.
 
 nrf_drv_wdt_channel_id m_channel_id;
 
 void wdt_event_handler(void) { NVIC_SystemReset(); }
 
 int main(void) {
     uint32_t err_code = NRF_SUCCESS;
 
     debug_init();
     led_on(1000);
     led_off(0);
 
     nrf_drv_wdt_config_t wdt_config = {
         .behaviour = NRF_WDT_BEHAVIOUR_RUN_SLEEP_HALT,
         .reload_value = 10000,
         .interrupt_priority = APP_IRQ_PRIORITY_HIGH
     };
     err_code = nrf_drv_wdt_init(&wdt_config, wdt_event_handler);
     APP_ERROR_CHECK(err_code);
 
     err_code = nrf_drv_wdt_channel_alloc(&m_channel_id);
     APP_ERROR_CHECK(err_code);
 
     nrf_drv_wdt_enable();
 
     while (1) {
         led_on(50);
         led_off(950);
     }
}

[Stefan Birnir Sverrisson]

Hi Lee

Have you seen the WDT example in the nRF51 SDK? I suspect you are missing to initialize the low frequency clock, which the WDT requires. Something like

nrf_drv_clock_init(NULL);

[Stefan Birnir Sverrisson]

Hi Lee

The chip is in debug mode after you flash the code. After you power reset it will go into normal mode.

There are some pan issues for the WDT in the PAN but I do not see them directly map to your situation. The nRF51822 CEAA could anyway be both second or third revision. What are the full chip markings on your nRF51 chip, is it second or third revision? The nRF51 SDK 8.1.0 is not compatible with the second revision, see the nRF51 Compatibility matrix. So if you have the second revision hardware and use it with SDK 8.1.0, that might be an issue.