Anyone who has used a Raspberry Pi for a project has probably encountered a lock-up at some point or another, which often results in a hard reset. While there are software fixes that can reset the Pi, any peripherals connected via USB may still be locked, and only a full power cycle will solve the problem. Sequent Microsystems has designed a Hardware Watchdog HAT that helps solve that issue by protecting the Raspberry Pi from software freezes and even acting as a power manager.
The Hardware Watchdog HAT and Power Manager is compatible with any Raspberry Pi with a 40-pin connector and features a pair of power connectors- a micro USB port equipped on top of the board, plus a 2.1mm barrel connector on the bottom. Sequent explains, “Since the watchdog can interrupt the power supply to the Raspberry Pi, the supply source needs to be connected to the watchdog. For this purpose, the watchdog has a micro-USB connector similar to the one present on Raspberry Pi.”
The Hardware Watchdog HAT is outfitted with an STM32F030F4P6 MCU with an A03401 MOSFET power switch, as well as an onboard resettable fuse. Users can program the HAT’s delay and how often the software is reset, and if the expected reset doesn’t happen, the HAT cuts power, waits for 10-seconds then restores power, and reboots the Raspberry Pi.
“The watchdog becomes operational after power-up and unless it receives a reset, after 120 seconds will cycle the Raspberry Pi power. The watchdog can be reset either by sending a command on the I2C port or by toggling a GPIO pin. If you plan to use the I2C port make sure you enable I2C communication from the “raspi-config” menu.”
Sequent Microsystems is currently crowdfunding their Hardware Watchdog HAT and Power Manager on Kickstarter, with pledges starting at $15.