Low power CM3 shutdown and i2c battery monitoring

nzbypaul · June 28, 2019, 9:22am

Hi all!! Just checking the validity of an idea hoping I can get some guidance before proceeding? I have a project that has a battery management interface via i2c. Ideally I would like the Balena to shutdown on low power (have already got this monitored and working) but keep the CM3 coproccessor operating and monitoring the battery via i2c and when its gets above X charge state start up the Balena again.

From looking through the various docs and forum posts I think this is possible but looking for input from the wider community for any advice before proceeding - I’m a bit new to this so trying to avoid attempting something that may or may not be possible to begin with and if others have done so before me then not re-inventing the wheel!

Any advice greatly appreciated

curcuz · June 28, 2019, 10:56am

Hi @nzbypaul! the way I would proceed based on your requirements would be to leverage the balenaFin co-processor for the battery management (you can remap i2c to the EXP headers) so that it can determine when to spawn or shutdown the Raspberry Pi Compute Module. To answer your main question: yes, it is possible with the balenaFin

nzbypaul · June 30, 2019, 8:20pm

Thanks for your reply! Just looking to whats involved in getting this off the ground and from the readme of the firmata flash application there isn’t support for the Fin 1.1 yet(?)

github.com

balena-io-playground/balena-fin-firmata-flash/blob/master/README.md

# balena-fin-firmata-flash

This is a balena application that allows to flash the balenaFin Coprocessor with the latest version of the [balenaFin Firmata](https://github.com/balena-io/balena-fin-coprocessor-firmata). For more information about Firmata, check out the official [repo](https://github.com/firmata/protocol). **This currently supports the balenaFin v1.0** (v1.1 will soon be supported as well).

### Getting started

1. Setup your balena account and push to your application following the [getting started](https://www.balena.io/docs/learn/getting-started/fincm3/python/#account-setup) guide.
2. Check the balenaCloud terminal for your application to see if your device has successfully connected and flashed the bootloader & firmata application for the Coprocessor.

### Checking Firmata is working correctly

The Firmata protocol should correctly output the messages `X ✔ firmware name` and `Y.Z ✔ firmata version` (where `Y` & `Z` are the current supported `MAJOR` & `MINOR` versions of firmata) when the balena application has been successfully started.

After starting, the balena application will perform a digital and analogue I/O test to validate that the pins are behaving correctly. **Please note, you should not have any devices connected to the USB hub during the test.**

In order to complete the tests connect jumper wires across the following pins:

|         |     Pin A      |       Pin B        |
|---------|----------------|--------------------|
| Digital |       2        |         1          |

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Is this still correct? If so, any idea when support will be added?

Cheers

curcuz · July 1, 2019, 9:54am

@nzbypaul while adding support for v1.1, we took the chance to improve the overall workflow and I’ve been personally testing it for weeks. We are going to release it this week, so stay tuned

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Low power CM3 shutdown and i2c battery monitoring

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