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Comment by nicolaslem | Hacker News Reader

For me the really cool thing with these XIAO modules is that they support charging a lithium cell via the USB port directly without any additional circuitry. I have turned one of them into to a wireless doorbell that get recharged via USB-C.

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Speaking of the doorbell project, I recently found this cool piano doorbell project, a beautiful-looking and sounding doorbell that looks like a miniature piano. It has five individual, fully functional piano keys. Each key, when pressed, plays a distinct note, sampled from a real piano: https://www.hackster.io/makestreme/a-piano-doorbell-that-sou...

About doorbells (and charging them): there exist battery-less wireless doorbells, they generate enough energy from pushing the button. I got some off aliexpress several years ago.

Yes, the project does not make a ton of sense but it was for me the opportunity to learn ESP32 and have some fun. The outdoor module is constantly in deep sleep and only wakes up for a few seconds when the button is pressed. I put a 1000 mAh cell as that was the biggest capacity that fit the enclosure, that's probably way too much as in deep sleep the ESP32 barely consumes anything.

The indoor module is plugged straight into a wall socket so no batteries. When someone is at the door I am notified by Michael Scott: https://www.youtube.com/watch?v=umDr0mPuyQc (maybe I will get tired of this, for now it's still fun)

Obviously it doesn't make that much difference for a fun project with a large 1000mAh battery, but <44 μA for deep sleep isn't very good.

https://archive.is/2YBHS with an nrf52840 you can get <1uA. It doesn't do wifi but long range BLE can go over 2km range.

Have you tested their newest XIAO MG24, based on Silabs? It's said the power consumption is even better than the nrf52840 model.

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