I have implemented the AB1805 watchdog / clock on my carrier boards (v1.5) and have been testing over the past 3 weeks. I have not seen any issues with the device not coming back from “Enable” sleep as was the case occasionally when I was using two separate devices (a watchdog for resets and an RTC for “Enable” sleep) in the previous design (v1.4). This is the schematic for the AB1805:
Note that the AB1805 has access to both the Enable and Reset (!RST) pins via separate connections.
However, I have decided that the benefits of “Enable” sleep are not enough to outweigh the costs - especially with the new Sleep 2.0 API. So, I use “ULTRA_LOW_POWER” sleep and save the toggling of the “Enable” pin as a last resort fix for connectivity issues using the deepPowerDown() command.
This has made the Boron code much simpler and more like the good old days when the Particle device had a real time clock like the Electron.
The good news is that, with a 2000mAH battery, these devices can work for up to a month without charging. I think that the combination of deviceOS LTS, Sleep 2.0, the new power management API and this watchdog timer reference design has finally brought us to a place where we can deploy devices with high reliability and low power consumption - knock on wood!
Hope this is helpful. I will keep you up to date as the number of deployed devices with this new design grows in the coming months.
Chip