[Chris2048]

Doesn't the ESP32 have something like this: a second low-power cpu (Ultra Low Power coprocessor) that can wake up the main processor periodically, and then turn it off for simple operations, such as timed sleeps or waiting for input (aka interrupts). Not sure how (volatile) memory is managed though, or is maintaining it is power-intensive.

[throwaway81523]

The ULP coprocessor still uses a small amount of power, as does its few KB of NVRAM. The idea of the intermittently powered FRAM thing is that it can be powered down completely, then start up again and continue from a checkpoint. I haven't read the paywalled article, but it looks to me like the main contribution in the project was hacking circuit python to transparently checkpoint itself every so often, so that it can restart when power is restored.

I don't really understand why they used the second (msp430) microprocessor, instead of add-on FRAM like this: https://www.adafruit.com/product/1895

It also seems to me that micropython is great for some things, but in this particular deployment it is increasing the hardware cost and complexity quite a bit.

[Chris2048]

Yep. I think for limited resources, micro-py is the wrong approach. That it is interpreted aside; I had a lua-based interpreter crash because the stack/heap in a nested routine (ie lots of nested fn calls) managed to fill up available memory.

[jhgb]

Sounds almost like an ideal use case for Oberon to me - perhaps with remoting the UI or something like that. Chances are that a full environment would still be smaller than this micro-py thingy, whatever that is.