Review on South Berkeley Electronics PiDog2 Raspberry by Tom Herman

Watchdog timers are unfamiliar to most, but as an engineer I can tell you that they are absolutely essential for highly reliable systems, especially those used in the field and are not easily obtained. One of the notable shortcomings of the Raspberry Pi lineup is its inability to recover from a system crash (or shutdown) without a full power outage. A power controlled watchdog corrects this error and results in a very reliable Pi. Until now adding an external hard power off watchdog to the Pi has been a do-it-yourself task, I usually have the problem with a small microcontroller, relays and bypassed coding. I was glad that one of my research turned up a PiDog2 and I bought a pair to test. This is a very simple board (as it should be!) that uses a FET to switch the power supply under the control of a microcontroller, with a simple software interface with two timers showing the "on" and "off" times count depending on the mode . Writing a new value to the "on" timer resets the watchdog timer. A simple script could write this value regularly (or alternatively not write this value to force a reset). Add in a few tests to make sure your Pi is working properly, and you now have a Pi that is unlikely to fail no matter where it is. I can confirm that the board works as intended and that the software available on github supports it without undue hassle. At least in my case it worked fine on Python 2.x with a change in the script header (use of Python 3 is advertised). microcontrollers, so don't expect to-the-second precision) and the use of JST connectors for voltage sensing (probably a design choice to prevent reverse polarity) - although two JST pigtails are thoughtfully included for this. Requiring soldering might be a downside for some, but it does give you the option of using an extended header to put another HAT on top of the watchdog. It's a little pricey - almost the cost of the Pi itself - though that must be expected of low volume hardware catering for a unique market.