Watchdog Timers in Product Development

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MTech1

Joined Feb 15, 2023
161
Have you ever used a watchdog timer in your product development?

I noticed it helps reset the system, but since we have hardware reset buttons too, what's the main reason for using a watchdog timer in product development?
 

Ya’akov

Joined Jan 27, 2019
9,230
A watchdog timer is a hardware device (which may be an onboard peripheral or an independent of the MCU.) The watchdog implements a countdown timer which is periodically reset by code running on the MCU’s MPU. If the MPU fails to execute the reset code before the timer elapses, either because it goes stupid or it is stuck in a loop, the watchdog operates MCU’s RESET or NMI line to force a reboot.

The watchdog is an independent hardware component that doesn’t depend on the MCU’s processor for its own operation so it can act to reset an unattended MCU when a lockup is detected. A manual reset button can’t help you if the device is embedded in an inaccessible location or it is a critical component of an unattended system.

For example, you might put a watchdog timer on an Internet modem so if it stopper operating it would reboot itself without user intervention. It might also be employed in remote sensors that could start up in an unknown state where the processor fails to execute code but the watchdog, being hardware, doesn’t care and simply reboots the processor at the end of timeout to correct the startup fault.
 

MrChips

Joined Oct 2, 2009
30,925
Have you ever used a watchdog timer in your product development?

I noticed it helps reset the system, but since we have hardware reset buttons too, what's the main reason for using a watchdog timer in product development?
In product development, one would disable the watchdog timer because it interferes with debugging. After the product is complete, one might choose to enable the watchdog timer with correct updates in final product release.
 

ericgibbs

Joined Jan 29, 2010
18,987
Hi MT,
I used them on all the micro equipment I manufactured.
Reason being most of my equipment was for Marine & Land Surveying which meant mobile/battery supplies, which were noisy and temperamental and so glitched out the micro's

E
 
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