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HAT offers hardware watchdog for Raspberry Pi

Sep 23, 2019 — by Eric Brown — 1899 views

On Kickstarter: Sequent Microsystems has launched a $15 “Hardware Watchdog HAT & Power Manager for Raspberry Pi” for protecting against software lock-ups.

Hardware-based watchdog timers are usually standard equipment on industrial computers, but are rarely seen on Linux hacker boards. Sequent Microsystems, which has previously launched Raspberry Pi add-ons such as the MegaIO-IND home automation board, has now successfully launched a Hardware Watchdog HAT & Power Manager for Raspberry Pi. The HAT is available on Kickstarter through Oct. 17 for $15 for Jan. 2020 delivery or $20 for Nov. 2019 delivery.



Hardware Watchdog HAT & Power Manager for Raspberry Pi and block diagram
(click images to enlarge)

The watchdog HAT will ensure that any Pi with a 40-pin GPIO connector will continue to run despite software lock-ups. It ensures continual power to the Pi and other stacked HATs by offering both micro-USB port and a DC barrel jack. The HAT itself consumes less than 5mA.

Raspbian offers a software-based watchdog, but it may not be reliable enough for remote, mission-critical applications in which the Pi must be guaranteed to run continually. “The software watchdog will reset your Pi, but any intelligent peripheral plugged into the USB port might still be locked-up,” says the Hardware Watchdog HAT Kickstarter announcement. “Only a full power cycle will bring your system back to life.”

The 65 x 20mm HAT, which we saw on Geeky Gadgets, is also equipped with a power management app that can program the Pi to shut down and power up at scheduled times. You can program the watchdog delay and indicate how often it should be reset. If the expected reset does not come, the watchdog cuts the power, waits 10 seconds and restores the power with a reboot. The watchdog can be reset either by sending a command via I2C or by toggling a GPIO pin.

If you’re using batteries, the HAT will let you check the supply voltage. You can program the Pi to shut down when the level drops below a set value.

 
Further information

The Hardware Watchdog HAT & Power Manager for Raspberry Pi is available $15 or $20 for delivery in Jan. 2020 or Nov. 2019, respectively. The $20 package includes free shipping, but is only available for U.S. customers. More information may be found on Sequent Microsystems’ Kickstarter page.
 

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