Reading the value of a GPIO pin works, but onFalling, etc. fail to trigger

[bottlehall]

Board Type

RaspberryPi3 Model B

Operating System

Ubuntu 24.04.1 LTS

Swift Version

Swift version 5.10.1 (swift-5.10.1-RELEASE)
Target: aarch64-unknown-linux-gnu

Installed from swiftARM as binary

Description

A KY-038 sound sensor's digital output (triggered when a threshold is reached) is connected to GPIO pin 23. The board can run with 3.3-5V supply. I am running it at 5V without pull-up resistors.

I have cobbled this code from several sources. It executes without error but none of the closures are triggered.

import Foundation
import SwiftyGPIO

let gpios = SwiftyGPIO.GPIOs(for:.RaspberryPi3)
var gp = gpios[.P23]!

gp.direction = .IN
gp.bounceTime = 0.5

gp.onRaising{
    gpio in
    print("Transition to 1, current value:" + String(gpio.value))
}

gp.onFalling{
    gpio in
    print("Transition to 0, current value:" + String(gpio.value))
}

gp.onChange{
    gpio in
    gpio.clearListeners()
    print("The value changed, current value:" + String(gpio.value))
}

RunLoop.main.run()

If I replace the RunLoop.main.run() with:

while true {
    print("GPIO.value=\(gp.value)")
}

Then I can see the value changing from 0 to 1 appropriately. I have tried changing .pull but this has no effect.