[feature] BMA421 integration

[sdorre]

The Pinetime has an accelerometer integrated. Let's try to get it to work.

The hardware is a Bosch BMA421.
One guy already has it working with Micro Python on the pinetime. He wrote the following code:
https://github.com/daniel-thompson/bma42x-upy

[endian-albin]

As long as the implemention is all free software, then yeah!

[sdorre]

I pushed a branch if you want to have a look at the alpha.
I did not get the chance to see other than 0 for the step counter so far.
I broke my debug setup. I will fix it on monday.

[endian-albin]

This looks really promising! The step counter appears to be accurate from a very short test. I'm a bit suspicious about the thermometer though. I don't think it exists in the BMA421 component that's on the PineTime, see the flyer for example). Also, I went outside where it's more than 10 degrees colder right now and the temperature dropped just one degree.

[endian-albin]

Ah, so the thermometer is for the accelerometer chip itself... It shouldn't be used to measure the outside temperature.

[sdorre]

I made some changes on my PR. It is now running on interrupt without the config blob.
So only acceleration data is accessible.

@endian-albin Do you want me to rewrite it so we get rid of the BSD-3 Code from Bosch ?

[endian-albin]

I made some changes on my PR. It is now running on interrupt without the config blob.
So only acceleration data is accessible.

OK, can you think of a use case for this? Even if this is good for the future, I prefer to have at least some new feature that makes use of added code. Could we use it combined with a repeatable timer (80--100 ms) that checks the XYZ values for a position where a human might look at it and then light up the display ("lift to wake")?

@endian-albin Do you want me to rewrite it so we get rid of the BSD-3 Code from Bosch ?

If you think you can also make it smaller, better, etc and you do a proper rewrite like ATCWatch did. That might also make it easier to upstream. Otherwise, BSD-3-Claue is compatible with Apache 2.0 so you could also simply add a copyright line and Apache 2.0 SPDX line on top of the BSD-3 header text. Then you should also add a BSD-3-Clause SPDX line close to the Bosch copyright line, maybe just above it.