Add support for NAU7802

[amotl]

We would like to add support for the Nuvoton NAU7802 24bit 2ch AFE for bridge sensors by @OpenNuvoton.

@ClemensGruber just found the nau7802py implementation by @longapalooza, who ported the SparkFun Qwiic Scale Arduino library by @nseidle to CPython. Thanks, Will! Edit: I also just disovered another CPython implementation PyNAU7802 by @BrunoB81HK. Thanks, Bruno!

Now, we are aiming to support this within Terkin on
a) RaspberryPi by using the nau7802.c Linux IIO implementation.
b) MicroPython by adding appropriate support through the nau7802py implementation, which will have to be adjusted for MicroPython.

[amotl]

a) RaspberryPi by using the nau7802.c Linux IIO implementation.

@MKO1640 worked on this, see #105 and Erschließung des HX711 Treibers für Linux-IIO.

[amotl]

b) MicroPython by adding appropriate support through the nau7802py implementation, which will have to be adjusted for MicroPython.

I just discovered a CircuitPython implementation, cedargrove_nau7802.py by @CedarGroveStudios, see also [1]. Thanks!

Code snippets for calibration and reading can be found at clue_scale_calibrate.py and clue_scale_code.py.

[1] https://twitter.com/CedarGroveMakr/status/1332083784989065216

[amotl]

Hi again,

@ProblemSolved99 is also looking into having MicroPython support for the NAU7802 and just asked at @longapalooza's repository, see longapalooza/nau7802py#2.

With kind regards,
Andreas.