Using a Raspberry Pi to end an iPhone phone call

Headphone breakout switch

A user can end a phone call by clicking the headphone switch.
A program can end a phone call by closing a headphone breakout switch.

Advantages

• Fun!

Disadvantages

• Overly complicated compared to springboard solution.
• Not very general, clicking switch works for only a few actions
• Requires some hardware
• Could accidentally damage phone or raspberry pi or yourself. If you are careful I think the risks are low, but no warranty!
• Not directly applicable to phone without a headphone jack, but could substitute an actuator to mechanically press switch.

I made a prototype.

Prototype system

The system has several parts

• Phoney app
• Phoney XCUITest
• iPhone
• Raspberry Pi
• pi_gpio_service
• Relay
• Cable, relay to breakout switch
• Headphone breakout switch
• Headphone
• Cable, breakout switch to phone

Phoney app, request_web_service_end_call branch

https://github.com/beepscore/Phoney

It has a button to call a phone number.

Phoney XCUITest

XCUITest runs the test from Swift on iOS. It needs a way to ask the raspberry pi to end the call. I didn't see an easy way to issue a system call or spawn a process.
So XCUITest makes an http request to an external web server, ask it to close switch.

iPhone

Making a phone call requires a device, not a simulator.

Raspberry Pi

The Raspberry Pi runs a web service and connects to a relay board.

pi_gpio_service

runs on the local wifi network.
https://github.com/beepscore/pi_gpio_service

Server security

Currently the prototype service runs on the local network, and is not very secured.
By default an iOS app that talks with a web service requires https and TLS 1.2.
Apparently XCUITest doesn't require this, at least when talking with a service on the local network.

Relay

The relay acts like the headset "end call" switch, momentarily shorting the headset microphone contact to ground.

Cable, relay to breakout switch

Coaxial splitter, 1 female to 2 males (female unused)

Headphone breakout switch

Making an iPhone Headphone Breakout Switch

Headphone

A standard iPhone wired headphone with a 4 connector plug.

Cable, breakout switch to phone

Connects breakout switch to phone. 3.5 mm 4 conductor male to 3.5 mm 4 conductor male

Test Flow

• The XCUITest starts the Phoney app on the iOS device

• 

• 

• The test taps the alert "Call" button

• 

• iOS calls callObserver callChanged with call.hasConnected
• The iOS XCUITest sends an http request to the pi web service to end the call.

let urlString = "https://10.0.0.4:5000/api/v1/gpio/end-phone-call/"
let url = URL(string: urlString)!

var request = URLRequest(url: url)
request.setValue("application/json", forHTTPHeaderField: “Content-Type")
request.httpMethod = "POST"

let task = URLSession.shared.dataTask(with: request) { data, response, error in
// ...
}

task.resume()

• The pi's python web service routes the incoming request to handling function gpio_end_phone_call.

# POST but not GET because GET should not change any state on the server
@app.route("/api/v1/gpio/end-phone-call/", methods=['POST'])
def gpio_end_phone_call():
    return end_phone_call()

• The pi momentarily closes the relay.

def end_phone_call():
    """
    simulate manually clicking headphone switch to end a phone call
    :return: result of last pin_update
    """
    relay0 = pfd.output_pins[0]
    relay1 = pfd.output_pins[1]

    # turn relay0 on
    relay0.value = 1

    delay_seconds = 0.4

    sleep(delay_seconds)

    # turn relay0 off
    relay0.value = 0

• In the breakout switch this shorts the headphone microphone and ground contacts.
• iOS ends the call
• iOS calls callObserver callChanged with call.hasEnded
• The pi web service sends a response to XCUITest
• One or more test expectations are fulfilled.

Test failure

The test adds a UIInterruptionMonitor, then interacts with the app UI via swipeUp or tap.
Without this, the iOS phone call alert handler doesn't fire.
But with it, the test usually ends with error ~ "Application for Target Application 0x1c40af060 is not foreground.".
I fixed the failure by switching to springboard. That made this approach obsolete.

References

XCUITest iOS app phone call

Phoney

Phoney is an iOS application to experiment with testing phone calls.
https://github.com/beepscore/Phoney

request_web_service_end_call branch

Uses XCUITest to make an http request to an external web server, asks it to end call by closing switch.

master branch

Uses XCUITest with Springboard to tap End call button.

pi_gpio_service

Make a simple Python flask web service to read and write Raspberry Pi GPIO.
https://github.com/beepscore/pi_gpio_service

Relay

PiFace Digital 2

purchased from Vetco Electronics

https://www.element14.com/community/docs/DOC-69001/l/piface-digital-2-for-raspberry-p
https://www.piface.org.uk/products/piface_digital/

Headphone breakout switch

Making an iPhone Headphone Breakout Switch