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crasbe merged 5 commits into from
Sep 5, 2025
Merged

feather-m0: add support for saul_bat_voltage #21022

crasbe merged 5 commits into from
Sep 5, 2025

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@miri64 miri64 commented Nov 21, 2024 •
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Contribution description

When trying to get #21018 to work for the feather-m0, the ADC line only returned -1, so I removed this from #21018.

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.

  • feather-m0, feather-m0-lora, or feather-m0-wifi

Issues/PRs references

Based on #21018

@miri64 miri64 mentioned this pull request Nov 21, 2024
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@github-actions github-actions bot added Area: build system Area: Build system Area: drivers Area: Device drivers Area: boards Area: Board ports Area: SAUL Area: Sensor/Actuator Uber Layer labels Nov 21, 2024
crasbe
crasbe reviewed May 16, 2025
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Some small nitpicks, otherwise this looks very good.

It will require a rebase after #21349.

@crasbe crasbe added the Type: enhancement The issue suggests enhanceable parts / The PR enhances parts of the codebase / documentation label May 16, 2025
@miri64 miri64 force-pushed the saul_bat_voltage/enh/feather-m0-config branch 2 times, most recently from cb3cbc6 to 1b578fc Compare May 20, 2025 11:42
@github-actions github-actions bot removed the Area: build system Area: Build system label May 20, 2025
@miri64 miri64 force-pushed the saul_bat_voltage/enh/feather-m0-config branch from abb0908 to fbe894f Compare May 20, 2025 11:49
@crasbe crasbe added the CI: ready for build If set, CI server will compile all applications for all available boards for the labeled PR label May 22, 2025
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riot-ci commented May 22, 2025 •
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Murdock results

✔️ PASSED

08b6936 feather-m0: add support for saul_bat_voltage

Success Failures Total Runtime
576 0 576 05m:24s

Artifacts

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miri64 commented May 23, 2025

👍 now only some actual tests are needed 😅

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mguetschow commented May 23, 2025

👍 now only some actual tests are needed 😅

didn't you have such hardware at home?

@crasbe crasbe marked this pull request as ready for review May 23, 2025 13:52
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crasbe commented May 23, 2025

I have a Feather-M0 at home, but it's difficult to flash with WSL and even converting the .hex to a .uf2 file worked, but I can't access the serial terminal.
One of these days I'll remember to bring the Feather to work and test it there... hopefully 🫠

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crasbe commented May 23, 2025

Good news: I just remembered that my server runs Ubuntu Server and I can use that to test the PR.
Bad news: it doesn't work 😅

It always shows -6mV, regardless of whether the BAT pin is left floating (and the charge controller just seems to cycle, at least the LED is blinking very fast) or connected to 3.3V, which makes the LED light up permanently.

2025-05-23 17:11:34,132 # -gfbe894-saul_bat_voltage/enh/feather-m0-config)
2025-05-23 17:11:34,133 # Welcome to RIOT!
2025-05-23 17:11:34,133 #
2025-05-23 17:11:34,136 # Type `help` for help, type `saul` to see all SAUL devices
2025-05-23 17:11:34,137 #
> help
2025-05-23 17:11:36,357 # help
2025-05-23 17:11:36,359 # Command              Description
2025-05-23 17:11:36,361 # ---------------------------------------
2025-05-23 17:11:36,364 # pm                   interact with layered PM subsystem
2025-05-23 17:11:36,367 # ps                   Prints information about running threads.
2025-05-23 17:11:36,370 # saul                 interact with sensors and actuators using SAUL
2025-05-23 17:11:36,372 # version              Prints current RIOT_VERSION
2025-05-23 17:11:36,374 # bootloader           Reboot to bootloader
2025-05-23 17:11:36,376 # reboot               Reboot the node
> saul
2025-05-23 17:11:37,289 # saul
2025-05-23 17:11:37,290 # ID    Class           Name
2025-05-23 17:11:37,291 # #0    SENSE_VOLTAGE   BAT
2025-05-23 17:11:37,292 # #1    ACT_SWITCH      LED(Red)
> saul read 0
2025-05-23 17:11:41,699 # saul read 0
2025-05-23 17:11:41,701 # Reading from #0 (BAT|SENSE_VOLTAGE)
2025-05-23 17:11:41,703 # Data:              -6 mV
saul read 0
2025-05-23 17:13:34,444 # saul read 0
2025-05-23 17:13:34,446 # Reading from #0 (BAT|SENSE_VOLTAGE)
2025-05-23 17:13:34,448 # Data:              -6 mV
>

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crasbe commented May 23, 2025

I just ran the tests/periph/adc test and this is the output from connecting BAT to GND with an 82 Ohm resistor (I totally didn't try it with a jumper and crash the board 👀 ) and to +3.3V.

Two things are evident here: connecting it to 3.3V does not show anything, therefore the range of the battery reading might be incorrect (wrong AREF perhaps?) and two resolutions show -1, which indicates that they are not supported.
-1 * 2 * 3300 / 1024 = -6.44 ~ -6

2025-05-23 17:18:21,092 # ADC_LINE(0): -1 255 1023 4095    -1 65520
2025-05-23 17:18:21,095 # ADC_LINE(1): -1 255 1023 4095    -1 65520
2025-05-23 17:18:21,097 # ADC_LINE(2): -1 255 1023 4095    -1 65520
2025-05-23 17:18:21,099 # ADC_LINE(3): -1 255 1023 4095    -1 65520
2025-05-23 17:18:21,101 # ADC_LINE(4): -1 255 1023 4095    -1 65520
2025-05-23 17:18:21,103 # ADC_LINE(5): -1 255 1023 4095    -1 65520
2025-05-23 17:18:21,105 # ADC_LINE(6): -1  84  338 1348    -1 21622
2025-05-23 17:19:53,376 #
2025-05-23 17:19:53,477 # ADC_LINE(0): -1 255 1023 4095    -1 65520
2025-05-23 17:19:53,479 # ADC_LINE(1): -1 255 1023 4095    -1 65520
2025-05-23 17:19:53,481 # ADC_LINE(2): -1 255 1023 4095    -1 65520
2025-05-23 17:19:53,483 # ADC_LINE(3): -1 255 1023 4095    -1 65520
2025-05-23 17:19:53,485 # ADC_LINE(4): -1 255 1023 4095    -1 65520
2025-05-23 17:19:53,487 # ADC_LINE(5): -1 255 1023 4095    -1 65520
2025-05-23 17:19:53,489 # ADC_LINE(6): -1 255 1023 4095    -1 65520

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crasbe commented May 23, 2025

More testing, now with lab supply and Multimeter:
Real Voltage: 0.81V
Saul Readout: 2.68V

Real Voltage: 1.29V
Saul Readout: 4.28V

Real Voltage: 1.60V
Saul Readout: 5.30V

Real Voltage: 1.98V
Saul Readout: 6.53V (About at the end of the scale)

Real Voltage: 4.21V
Saul Readout: 6.59V (end of scale)

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miri64 commented May 24, 2025

More testing, now with lab supply and Multimeter: Real Voltage: 0.81V Saul Readout: 2.68V

Real Voltage: 1.29V Saul Readout: 4.28V

Real Voltage: 1.60V Saul Readout: 5.30V

Real Voltage: 1.98V Saul Readout: 6.53V (About at the end of the scale)

Real Voltage: 4.21V Saul Readout: 6.59V (end of scale)

That seems too big. :-/

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miri64 commented May 24, 2025

So why did you move this PR out of draft stage? ;-)

@miri64 miri64 added the State: WIP State: The PR is still work-in-progress and its code is not in its final presentable form yet label May 24, 2025
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crasbe commented May 24, 2025

So why did you move this PR out of draft stage? ;-)

Because I don't consider this PR to be in the draft stage, it's very much close to completion and there is probably just an unrelated bug somewhere else.

@crasbe crasbe added the State: waiting for other PR State: The PR requires another PR to be merged first label May 24, 2025
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crasbe commented May 24, 2025

After rebasing to include #21508 and applying the suggestion to change the ADC channel from 7 to 6, this is what the output looks like:

2025-05-24 16:59:10,998 # -g7efa8f-saul_bat_voltage/enh/feather-m0-config)
2025-05-24 16:59:11,000 # Welcome to RIOT!
2025-05-24 16:59:11,000 #
2025-05-24 16:59:11,003 # Type `help` for help, type `saul` to see all SAUL devices
2025-05-24 16:59:11,003 #
> saul read 0
2025-05-24 16:59:13,813 # saul read 0
2025-05-24 16:59:13,816 # Reading from #0 (BAT|SENSE_VOLTAGE)
2025-05-24 16:59:13,817 # Data:             825 mV
>

However one thing I wondered in general: Why does this approach not use the periph_vbat feature that the STM32 Nucleos use?

@crasbe crasbe removed the State: waiting for other PR State: The PR requires another PR to be merged first label May 24, 2025
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miri64 commented May 26, 2025

After rebasing to include #21508 and applying the suggestion to change the ADC channel from 7 to 6, this is what the output looks like:

2025-05-24 16:59:10,998 # -g7efa8f-saul_bat_voltage/enh/feather-m0-config)
2025-05-24 16:59:11,000 # Welcome to RIOT!
2025-05-24 16:59:11,000 #
2025-05-24 16:59:11,003 # Type `help` for help, type `saul` to see all SAUL devices
2025-05-24 16:59:11,003 #
> saul read 0
2025-05-24 16:59:13,813 # saul read 0
2025-05-24 16:59:13,816 # Reading from #0 (BAT|SENSE_VOLTAGE)
2025-05-24 16:59:13,817 # Data:             825 mV
>

Is that the expected output?

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miri64 commented May 26, 2025

However one thing I wondered in general: Why does this approach not use the periph_vbat feature that the STM32 Nucleos use?

Because I, and apparently the reviewers of #21018, did not know about it 😅

Also: Is it exposed via SAUL? For my use-case (advertising the battery voltage via skald_bthome), I need that.

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crasbe commented May 27, 2025 •
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Is that the expected output?

Yes.

However one thing I wondered in general: Why does this approach not use the periph_vbat feature that the STM32 Nucleos use?

Because I, and apparently the reviewers of #21018, did not know about it 😅

Also: Is it exposed via SAUL? For my use-case (advertising the battery voltage via skald_bthome), I need that.

Not yet, because the VBat of the STM32s is more for battery backup of the RTC etc.
You can read the voltage, but it doesn't have as much of a practical usecase as the Lipo monitor of the Feathers.

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miri64 commented May 27, 2025

Not yet, because the VBat of the STM32s is more for battery backup of the RTC etc. You can read the voltage, but it doesn't have as much of a practical usecase as the Lipo monitor of the Feathers.

So that is another reason :-) But I mean, there is nothing preventing us from merging the two features in the future.

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crasbe commented Jun 4, 2025

This has to be rebased after #21504.

It's fine for me if (for the time being) we have two similar features, but I'd like to have to cross-referencing in the documentation and/or an issue to keep track of eventually merging them and/or adding SAUL for periph_vbat.

@crasbe crasbe added State: waiting for author State: Action by the author of the PR is required State: needs rebase State: The codebase was changed since the creation of the PR, making a rebase necessary labels Jul 28, 2025
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crasbe commented Jul 28, 2025

Ping @miri64 :)

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saul_bat_voltage: add output unit to documentation
ef5f422 
Co-authored-by: crasbe <crasbe@gmail.com>
@miri64 miri64 force-pushed the saul_bat_voltage/enh/feather-m0-config branch from fbe894f to e044b00 Compare September 5, 2025 08:05
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miri64 commented Sep 5, 2025

Rebased and adopted for 60eaa5a

@miri64 miri64 removed State: waiting for author State: Action by the author of the PR is required State: needs rebase State: The codebase was changed since the creation of the PR, making a rebase necessary labels Sep 5, 2025
@crasbe crasbe removed the State: WIP State: The PR is still work-in-progress and its code is not in its final presentable form yet label Sep 5, 2025
@miri64 miri64 force-pushed the saul_bat_voltage/enh/feather-m0-config branch from 257f2df to 1fc77e7 Compare September 5, 2025 08:12
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@miri64 miri64 force-pushed the saul_bat_voltage/enh/feather-m0-config branch from 6fa85b9 to e59e9b6 Compare September 5, 2025 08:26
@miri64 @crasbe
feather-m0: add support for saul_bat_voltage
08b6936 
Co-authored-by: crasbe <crasbe@gmail.com>
@miri64 miri64 force-pushed the saul_bat_voltage/enh/feather-m0-config branch from e59e9b6 to 08b6936 Compare September 5, 2025 08:27
@crasbe crasbe mentioned this pull request Sep 5, 2025
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Merged via the queue into RIOT-OS:master with commit 1be70cf Sep 5, 2025
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@benpicco benpicco added this to the Release 2025.10 milestone Dec 3, 2025
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