• State Verified Answer
  • Replies 11 replies
  • Subscribers 67 subscribers
  • Views 6855 views
  • Users 0 members are here
Attachments (0)
Nordic Case Info
  • Case ID: 114606
Options
This post is older than 2 years and might not be relevant anymore
More Info: Consider searching for newer posts

Watchdog while in sd_app_evt_wait

Adrian Eggenberger

Hi

I've discovered last week some unexpected resets by the watchdog. I guess I've the explanation and the workaround for the behavior, but it would be great to have this assumption confirmed. Maybe some other peoples have similar behaviors.

The firmware is built on SDK11 and is based on a simple peripheral project. We have a watchdog configured with a time of five seconds and not running in sleep mode. We establish a connection from a smart device and than do no real data transfer. The call of sd_app_evt_wait by the application never returns, because the application has nothing to do (no interrupt causing the wakeup). After around 80 seconds the system resets caused by the watchdog.

My assumption is, that the softdevice internally wakes up for handling the BLE connection intervals. These ISR's are quite short, but the Watchdog counts up a bit at any wakeup. The application won't reset the watchdog because the call of sd_app_evt_wait never returns.

The solution I have is to configure at least a timer that forces the function sd_app_evt_wait to leave from time to time.

Can someone confirm this behavior? What is the best way to work around it?

Regards Adrian

Parents
  • 0

    and for your case you have a very simple solution also. When you're in your very, very low-power mode, don't use sd_app_evt_wait(), use __wfe(). sd_app_evt_wait() is only an optimised version of __wfe() anyway which filters out system events so you are only 'woken' on user events. Since the events at that point are so rare, it really doesn't matter, so use __wfe() and just feed the watchdog each time. Use sd_app_evt_wait() for the other places in your code where you are advertising or in connection and there will be lots of system events.

Reply
  • 0

    and for your case you have a very simple solution also. When you're in your very, very low-power mode, don't use sd_app_evt_wait(), use __wfe(). sd_app_evt_wait() is only an optimised version of __wfe() anyway which filters out system events so you are only 'woken' on user events. Since the events at that point are so rare, it really doesn't matter, so use __wfe() and just feed the watchdog each time. Use sd_app_evt_wait() for the other places in your code where you are advertising or in connection and there will be lots of system events.

Children
No Data
Related