saul: initial import of saul_bat_voltage module

[miri64]

Contribution description

This exposes the battery measuring capabilities for feather-like boards (see, e.g., https://learn.adafruit.com/introducing-the-adafruit-nrf52840-feather/power-management-2#measuring-battery-3122383) into SAUL so that the output value is the voltage and provides support for 4 7 boards:

• feather-nrf52840-sense ( ✅ tested )
• feather-nrf52840 ( ✅ tested )
• particle-xenon ( ✅ tested )
• particle-argon ( 🟥 not tested, don't own the board )
• feather-m0, as well as its derivates, feather-m0-lora and feather-m0-wifi, ( 🟨 tested, but not working as expected¹ ), see saul: initial import of saul_bat_voltage module #21018 (comment)

Testing procedure

Flash example/saul to one (or ideally all) of the supported boards and use the CLI to read from the BAT registry entry. Here is a handy check list so reviewers might distribute the job among themselves. The bold ones are particularly important as I was unable to test them properly myself.

• feather-nrf52840-sense
• feather-nrf52840
• particle-xenon
• particle-argon
• feather-m0, feather-m0-lora, or feather-m0-wifi

Issues/PRs references

Used for testing the power consumption of #20996.

Footnotes

1. not sure if the board I used for testing is broken. It used to work 5 years ago, here is the app where I took the config from. Sadly, I did not find the LARP prop I integrated the board I used for that into. ↩

[maribu]

code looks good to me. I think @chrysn has plenty of particle boards, maybe also the one that still needs testing?

Was only soft-ACK as none of the requested tests seem to have been run.

[miri64]

1. not sure if the board I used for testing is broken. It used to work 5 years ago, here is the app where I took the config from. Sadly, I did not find the LARP prop I integrated the board I used for that into. ↩

I just remembered, that I also have a feather-m0-lora here. Same problem as with the bare feather-m0, so its definitely not the board: ADC line 7 samples constantly to -1, which results in -6mV being returned.

[miri64]

I am removing the feather-m0-part for now from this PR, so this can go ahead with the working configurations.

[miri64]

Moved to #21022

[chrysn]

I only have particle-xenon, but it works fine there. It reads a voltage of 4.458V, no matter whether the battery is connected or not (probably b/c I can't use serial w/o also powering the device). All my boards are xenon, but my understanding is that the differences between the particle boards are quite minimal.

[miri64]

It reads a voltage of 4.458V, no matter whether the battery is connected or not (probably b/c I can't use serial w/o also powering the device).

Here's some proof, that the value actually changes over time ;-)

[riot-ci]

Murdock results

✔️ PASSED

eddd93e particle-{argon,boron}: note that board_bat_voltage is untested

Success	Failures	Total	Runtime
10242	0	10246	17m:38s

Artifacts

• Documentation preview

[mguetschow]

Successfully tested on feather-nrf52840: With a 600mAh battery connected and one LED turned on, the reported voltage dropped from around 4100mV to 3600mV over night.

[mguetschow]

Successfully tested on feather-nrf52840: With a 600mAh battery connected and one LED turned on, the reported voltage dropped from around 4100mV to 3600mV over night.

The feather-nrf52840-sense also reports 3600mV with the same battery attached.

[miri64]

Anyone has an Argon lying around? Otherwise, can we just assume that it works, as they use the common interface?

[maribu]

Compromise: Let's merge this as is, but document that we did not test on Argon specifically, but are optimistic that it will just work due to the similarity? A one-line comment would be totally sufficient.

[miri64]

Let's merge this as is, but document that we did not test on Argon specifically, but are optimistic that it will just work due to the similarity? A one-line comment would be totally sufficient.

Where should this doc go then? To the header file of saul_bat_voltage or to the particle-argon doc?

[miri64]

Where should this doc go then? To the header file of saul_bat_voltage or to the particle-argon doc?

Done for the board(s). There is also the particle-boron, I noticed that only now.

[maribu]

Let's prioritize the release.