Raspberry Pi 4 Model B Change Events Won't Fire

[gestrich]

Bug Report: GPIO Event and Value Handling Discrepancy

Board Type

• Raspberry Pi 4 Model B Rev 1.4

Operating System

• Debian GNU/Linux 12 (bookworm)

Swift Version

• Swift 6.0.1
  Installed using swiftlang.xyz

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Description of the Issue

When using a button wired to GPIO 26 as an input, I encountered inconsistent behavior with GPIO event handling and value reading depending on the board configuration used.

• Using RaspberryPi4:

  • Issue: GPIO events (e.g., onChange) do not fire when pressing the button.
  • Observation: Manually reading GPIO.value reflects the correct value change when the button is pressed.

• Switching to RaspberryPi4_2024:

  • Issue: GPIO events now fire properly, but manually reading GPIO.value no longer returns the correct value.

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Investigation Findings

• The filenames in /sys/class/gpio/ match the IDs used in RaspberryPi4_2024, which are offset by 512 (e.g., /sys/class/gpio/gpio538/value for GPIO 26).
  Thus, RaspberryPi4_2024 seems necessary for proper event handling.

• However, the ids in RaspberryPi4_2024 appear to break the memory mapping.

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Workaround

Here's a workaround I'm currently using. This ensures that the memory address calculations work as they did in RaspberryPi4 but the filenames will be offset by 512 as done in RaspberryPi4_2024. I don't understand all the details of this class so its likely I'm missing some things.