feat: add GPIO pin interface with embedded-hal-async digital trait support by jerrysxie · Pull Request #21 · OpenDevicePartnership/pcal6416a

jerrysxie · 2025-11-25T15:26:18Z

Summary

Adds a GPIO pin interface to the PCAL6416A driver, enabling individual pin control through the embedded-hal-async digital traits (InputPin, OutputPin, StatefulOutputPin). This allows users to pass individual GPIO pins to HAL-generic drivers and async tasks.

Built on top of #20.

Changes

New types and API:

Port enum (Port0, Port1) and Pin enum (Pin0–Pin7) to model the device's 2×8 GPIO layout
IoPin struct representing a single GPIO pin with async read/write/toggle operations
SharedDevice wrapper using embassy_sync::Mutex for safe concurrent access across pins
SharedDevice::split() method returning an array of 16 IoPin instances

embedded-hal trait implementations:

embedded_hal::digital::ErrorType for IoPin
embedded_hal_async::digital::InputPin for IoPin
embedded_hal_async::digital::OutputPin for IoPin
embedded_hal_async::digital::StatefulOutputPin for IoPin
embedded_hal::digital::Error for Pcal6416aError

Device-level pin methods (sync + async):

is_pin_high / is_pin_low
set_pin_high / set_pin_low
is_set_pin_high / is_set_pin_low
toggle_pin

Concurrency model:

Replaced UnsafeCell-based interior mutability with embassy_sync::Mutex for safe shared access
Each IoPin holds a reference to the shared mutex, so multiple pins can be passed to independent async tasks

New dependencies:

embassy-sync 0.7.2
embedded-hal / embedded-hal-async patched from git for latest async trait definitions

Tests:

Comprehensive test coverage for all pin operations (both Port 0 and Port 1)
Tests for embedded-hal-async trait compliance
All async tests run under tokio

Usage example

let device = SharedDevice::new(Device::new(Pcal6416aDevice { addr_pin: AddrPinState::Low, i2cbus }));
let pins = device.split();

// Pass individual pins to different async tasks
let led_pin = pins[0];   // Port0, Pin0
let btn_pin = pins[8];   // Port1, Pin0

led_pin.set_high_async().await?;
let pressed = btn_pin.is_high_async().await?;

Needed to maintain semver

jerrysxie · 2025-11-25T15:26:37Z

@EmilNorden Thoughts?

Copilot

Pull request overview

This PR adds a GPIO interface for the PCAL6416A I/O expander driver, providing high-level pin manipulation APIs. The PR builds on top of #20 and increments the version to 0.3.0.

Key changes:

Introduces a Pin enum representing the 16 GPIO pins with helper methods for port/bit mapping
Adds pin manipulation methods: is_pin_high, is_pin_low, set_pin_high, set_pin_low, toggle_pin, is_pin_set_high, is_pin_set_low
Extends device register definitions with input ports and pull-up/down control registers

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 18 comments.

File	Description
src/lib.rs	Adds `Pin` enum and GPIO manipulation methods to the Device implementation; includes comprehensive test coverage
device.yaml	Defines INPUT_PORT0/1, PULL_UP_DOWN_ENABLE_PORT0/1, and PULL_UP_DOWN_SELECT_PORT0/1 registers with field-level documentation
Cargo.toml	Bumps version from 0.2.0 to 0.3.0

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src/lib.rs

device.yaml

src/lib.rs

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device.yaml

src/lib.rs

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src/lib.rs

EmilNorden · 2025-11-27T19:44:27Z

@EmilNorden Thoughts?

I think it's a great interface, creating a pin abstraction on top of the registers makes it so much easier to use correctly.
My only concern would be if there is a plan to go through with the proposal in issue #2 (I hope so!). That would render this interface obsolete. It's not fun to change up the public interface too much between releases, so it's just something to consider.

jerrysxie · 2025-12-11T00:48:36Z

@EmilNorden Thoughts?

I think it's a great interface, creating a pin abstraction on top of the registers makes it so much easier to use correctly. My only concern would be if there is a plan to go through with the proposal in issue #2 (I hope so!). That would render this interface obsolete. It's not fun to change up the public interface too much between releases, so it's just something to consider.

@EmilNorden Excellent point, the plan is to move toward embedded-hal impl, but I don't want to have a bunch of pins all have mutex protecting the driver instance they all shared. Let me brew on this a bit more.

Add comprehensive GPIO pin interface with individual pin control: - Implement IoPin type for individual pin operations - Add Device::split() method to create array of 16 IoPin instances - Support both sync and async pin operations (set/read/toggle) - Implement embedded-hal digital traits (InputPin, OutputPin, StatefulOutputPin) - Add full async GPIO methods to Device (set_pin_high_async, etc.) - Implement digital::Error trait for Pcal6416aError - Add comprehensive test coverage for pin operations and embedded-hal trait compliance - Temporarily disable unsafe_code lint to allow UnsafeCell for interior mutability The split() API enables passing individual pins to different functions while maintaining shared access to the underlying I2C device through safe interior mutability patterns.

Improved test coverage for pin operations by testing pins from both ports (port 0 and port 1) in each test case. This ensures the logic is correctly validated across different register addresses since the device has separate registers for each port. Changes: - Updated sync pin tests (is_high, is_low, set_high, set_low, toggle, is_set_high) to test both Pin0 (port 0) and Pin15 (port 1) - Updated async pin tests (is_high_async, is_low_async, set_high_async, set_low_async, toggle_async, is_set_high_async, is_set_low_async) to test both Pin0 and Pin15 - Added inline comments to test expectations for clarity

src/lib.rs

Replace the UnsafeCell-based interior mutability pattern with embassy-sync's Mutex for safe concurrent access to individual GPIO pins. Changes: - Add SharedDevice wrapper with Mutex<M, Device> - Update IoPin to use &Mutex instead of &UnsafeCell - Remove synchronous pin methods, keep only async variants - Implement embedded-hal-async traits instead of blocking traits - Update all tests to use SharedDevice and async patterns - Add embassy-sync dependency (0.7.2) - Re-enable unsafe_code lint (was commented out) - Add embedded-hal git patches for latest async traits This provides proper mutex-based synchronization for safe concurrent pin access in async contexts.

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Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

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src/lib.rs

Cargo.toml

src/lib.rs

jerrysxie · 2026-02-13T13:06:37Z

@EmilNorden @felipebalbi Please take a look at the async implementation of embedded-hal::digital.

Split the GPIO pin model into separate Port and Pin enums so that each pin is identified by a (Port, Pin) pair instead of a single Pin0-Pin15 value. - Add Port enum with Port0 and Port1 variants - Reduce Pin enum from 16 variants (Pin0-Pin15) to 8 (Pin0-Pin7) - Add port field to IoPin struct alongside existing pin field - Update all Device methods (sync and async) to accept (port: Port, pin: Pin) parameters - Replace if/else port checks with exhaustive match on Port enum - Update SharedDevice::split() to assign correct Port to each pin - Update all tests to use new (Port, Pin) API

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Copilot reviewed 2 out of 2 changed files in this pull request and generated 10 comments.

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src/lib.rs

Cargo.toml

src/lib.rs

`// SAFETY:` is reserved for `unsafe` blocks. These methods use safe async mutex locks.

- Add doc comments to SharedDevice struct and ::new() - Make SharedDevice.device field private

src/lib.rs

EmilNorden and others added 5 commits November 20, 2025 20:30

Updated device.yaml with more registers

c01e34e

added missing unit tests

121c98e

fixed merge conflict

f333e73

Bump version

83a3c6d

Needed to maintain semver

RFC provide GPIO interface for pcal6416a pins

9e30ca0

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jerrysxie added 2 commits February 8, 2026 08:12

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jerrysxie requested a review from williampMSFT February 13, 2026 13:04

jerrysxie added the enhancement New feature or request label Feb 22, 2026

jerrysxie changed the title ~~RFC: add GPIO interface~~ Add embedded-hal digital trait support Feb 22, 2026

jerrysxie changed the title ~~Add embedded-hal digital trait support~~ feat: add GPIO pin interface with embedded-hal-async digital trait support Feb 22, 2026

jerrysxie requested review from felipebalbi and kurtjd February 22, 2026 18:38

jerrysxie marked this pull request as ready for review February 22, 2026 18:38

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jerrysxie added 2 commits February 22, 2026 12:46

chore: remove invalid SAFETY comments

1661002

`// SAFETY:` is reserved for `unsafe` blocks. These methods use safe async mutex locks.

docs: add SharedDevice docs, make field private

c22c561

- Add doc comments to SharedDevice struct and ::new() - Make SharedDevice.device field private

jerrysxie force-pushed the add-gpio-interface branch from 19b3d53 to c22c561 Compare February 22, 2026 18:58

Merge branch 'main' into add-gpio-interface

1ea703b

jerrysxie mentioned this pull request Feb 22, 2026

New release for embedded-hal digital async traits rust-embedded/embedded-hal#727

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jerrysxie linked an issue Feb 27, 2026 that may be closed by this pull request

Extend PCAL6416A driver to implement digital::InputPin and digital::OutputPin from embedded-hal #2

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jerrysxie mentioned this pull request Feb 27, 2026

Patch the yaml file to repeat registers instead of copying the same thing on the manifest #22

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jerrysxie merged commit 07cccfc into OpenDevicePartnership:main Feb 27, 2026
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jerrysxie commented Nov 25, 2025 •

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