All,
I have been working with the good folks at the Colorado State University who are interested in building very low power sensors for agricultural use. We have both been using the Texas Instruments TPL watchdog chips but, we wanted a programmable version to enable some unique use cases. This work uses the DS1337/9 chips which are 3.3V, have battery backup and programmable alarms. This work could be especially interesting to folks using the Argon and Xenon chips which lack a Real Time Clock.
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Tying the Interrupt pin to the enable Pin on the new 3rd Gen Particle devices should reduce sleep power draw to almost nothing
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Using the programmable nature of the timer to enable adaptive sampling when tied to a hardware interrupt pin
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Use as an external watchdog timer with a programmable interval when tied to the reset pin
This is a work in progress but, I wanted to share as it seems to be a productive effort. Also, this is the first time I have modified a library from Arduino to Particle and, while functional, I am sure there is room for improvement. Also, I am not sure whether / how to submit this to be an official Particle Library as none currently exists for the Maxim DS1337/1339 chips.
Here are the Github repos:
Hardware - https://github.com/chipmc/DS1339-RTC
Firmware / Library - https://github.com/chipmc/RTC-Watchdog
If our testing goes well, next step would be to build a Featherwing that could be programmed for these three use cases.
Thank you as always for your support and your suggestions.
Chip