Use diozero for GPIO #2171

thatcomputerguy0101 · 2025-11-01T01:42:26Z

Description

The old GPIO abstraction was replaced with diozero, which supports most hardware running Linux due to its use of GPIO character devices provided by the Linux kernel. diozero also supports alternate providers if for some reason the character device API is insufficient. Certain capabilities outside of the character device API is also implemented for common hardware.

Custom GPIO commands are implemented via a custom diozero provider. The configuration for custom GPIO will need manually updated according to the Hardware Config documentation page.

This was tested on a RPi 5 with LL3 illumination LEDs and an RGB status led attached. All capabilities worked as expected. All 8 status LED colors were tested and functional via modifying the code. Basic functionality of custom GPIO was tested with dummy commands.

closes #2062

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Merge checklist:

Pull Request title is short, imperative summary of proposed changes
The description documents the what and why
If this PR changes behavior or adds a feature, user documentation is updated
If this PR touches photon-serde, all messages have been regenerated and hashes have not changed unexpectedly
If this PR touches configuration, this is backwards compatible with settings back to v2025.3.2
If this PR touches pipeline settings or anything related to data exchange, the frontend typing is updated
If this PR addresses a bug, a regression test for it is added

samfreund · 2025-11-01T01:54:41Z

Looks like tests need to be fixed.

samfreund · 2025-11-01T01:56:14Z

Also seems like you grabbed some commits off a different branch when you created this one. You can fix that using interactive rebase.

Gold856

Looks pretty good at first glance. The big question I have is boards that support setting LEDs via a command of some sort, but not via diozero. If we do want to support LEDs on that kind of board, we still need CustomGPIO (I think). If not, we should clean up our config to not have those command fields.

thatcomputerguy0101 · 2025-11-01T23:34:32Z

I am currently planning to leave custom GPIO commands unimplemented, since diozero should work for the vast majority of boards with built-in GPIO. An advanced user could inject an alternate provider invisible to the rest of PhotonVision if for some reason the built-in provider does not work. The diozero.devicefactory system property could be set from a Photon setting, which will try and load the specified class dynamically, but a user capable of adding another provider is likely also capable of modifying the service file that launches Photon to specify it there.

The commit history and unit tests will be fixed before the draft status of this PR is removed.

photon-core/src/main/java/org/photonvision/common/hardware/VisionLED.java

photon-core/src/test/java/org/photonvision/hardware/HardwareTest.java

photon-core/src/main/java/org/photonvision/common/hardware/VisionLED.java

photon-core/src/main/java/org/photonvision/common/util/math/MathUtils.java

thatcomputerguy0101 · 2025-11-06T16:22:56Z

I am revisiting custom GPIO before unmarking this as a draft. I have some new ideas on how to make that happen.

samfreund · 2025-11-06T17:05:56Z

Can we make a PR to https://github.com/PhotonVision/photon-image-modifier as well to remove the installation of pigpio which is no longer needed?

thatcomputerguy0101 · 2025-11-06T17:06:52Z

Can we make a PR to https://github.com/PhotonVision/photon-image-modifier as well to remove the installation of pigpio which is no longer needed?

This was on my plans.

thatcomputerguy0101 · 2025-11-09T02:23:23Z

I elected to break compatibility with the older GPIO commands due to differences in behavior for the new GPIO commands. Specifically, the presence of new GPIO command dictates if they are enabled, instead of the platform. Also, setPWMCommand now takes a decimal between 0.0 and 1.0, instead of an integer percentage.

photon-core/src/main/java/org/photonvision/common/configuration/HardwareConfig.java

photon-core/src/main/java/org/photonvision/common/hardware/HardwareManager.java

photon-core/src/main/java/org/photonvision/common/hardware/VisionLED.java

Gold856 · 2025-11-10T04:34:39Z

photon-core/src/main/java/org/photonvision/common/util/ShellExec.java

    }

-    private int doProcess(boolean wait, Process process) {
+    private synchronized int doProcess(boolean wait, Process process) {


Is this necessary? If so, why?

Without this, I would occasionally get an IllegalThreadStateException from the gobblers since they were overwritten by another thread and were already started. I know the default implementation of blink in diozero uses threads, and I believe threads are also used in the default shutdown process. An alternative to synchronizing this method would to be to remove all of its dependencies on class variables, which would break some of the other methods here.

Gold856 · 2025-11-10T04:36:35Z

...core/src/main/java/org/photonvision/common/hardware/GPIO/CustomDigitalInputOutputDevice.java

+    @Override
+    public void setMode(DeviceMode mode) {
+        if (mode == DeviceMode.DIGITAL_INPUT) {
+            getValue();


What does getting the value do here?

I assumed the getGPIO and setGPIO to also set the data direction of the request pin to input or output, respectively. This is also why I cache the output value instead of getting it.

photon-core/src/main/java/org/photonvision/common/hardware/GPIO/CustomDeviceFactory.java

thatcomputerguy0101 requested a review from a team as a code owner November 1, 2025 01:42

github-actions bot added the backend Things relating to photon-core and photon-server label Nov 1, 2025

thatcomputerguy0101 marked this pull request as draft November 1, 2025 01:43

github-actions bot added the documentation Anything relating to https://docs.photonvision.org label Nov 1, 2025

Gold856 requested changes Nov 1, 2025

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thatcomputerguy0101 force-pushed the diozero-gpio branch from d46aad5 to 2c18a10 Compare November 2, 2025 02:31

Gold856 requested changes Nov 4, 2025

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photon-core/src/main/java/org/photonvision/common/hardware/VisionLED.java Outdated Show resolved Hide resolved

photon-core/src/main/java/org/photonvision/common/util/math/MathUtils.java Outdated Show resolved Hide resolved

thatcomputerguy0101 added 10 commits November 8, 2025 20:51

Migrate GPIO control to diozero

99edd82

Update documentation to reflect the use of diozero

9866272

Remove custom gpio commands

62ce302

Update tests for diozero

c358ebf

Calculate brightness percentage as a floating point number

c1b04bf

Make for loops consistent in VisionLED

3534b9c

Deduplicate code in VisionLED.setINternal

112915f

Calculate brightness as a double

0177318

Add custom GPIO diozero provider

14d0596

Synchronize ShellExec doProcess to prevent race condition on gobblers

1915638

thatcomputerguy0101 force-pushed the diozero-gpio branch from 275fd35 to 1915638 Compare November 9, 2025 02:15

Add license header to new files

ea4c6c5

thatcomputerguy0101 mentioned this pull request Nov 9, 2025

Remove pigpio PhotonVision/photon-image-modifier#91

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thatcomputerguy0101 marked this pull request as ready for review November 9, 2025 02:19

Gold856 requested changes Nov 9, 2025

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photon-core/src/main/java/org/photonvision/common/configuration/HardwareConfig.java Show resolved Hide resolved

thatcomputerguy0101 added 2 commits November 9, 2025 05:35

Add missing fields to HardwareConfig string

19505f9

Fix usage of default device factory in native gpio test

c40eddb

Gold856 requested changes Nov 10, 2025

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thatcomputerguy0101 added 4 commits November 10, 2025 18:01

Replace Arrays.asList with List.of

570b914

Replace Closable with AutoClosable

911fb1b

Use coercion instead of casting

008b0bc

Remove unused device name from Custom GPIO adapter

fc8dc11

Use diozero for GPIO #2171

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Use diozero for GPIO #2171

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