"Mashing" smartphone GSP and Arduino sensor data

[justus.goergens@gmx.net]

[BUG] <location> sensor produces no data in BLE experiments on iOS

Hi, following up on this thread — I'm running into the exact issue described in point 2, where the library doesn't support GPS, and I've implemented the recommended workaround (replacing <sensor> with <location> in the input block). However, the GPS data never arrives on iOS, even though it works perfectly in standalone phyphox experiments.

Setup

• Board: Arduino Nano 33 BLE
  
• phyphox BLE library: 1.3.0
  
• phyphox app: version 1.2, build 17272, file format 1.19
  
• Device: iPhone 13 mini
  
• iOS: 26.4.2
  

What works

• The BLE IMU data streams perfectly — accelerometer and gyroscope graphs update in real time
  
• The built-in phyphox Location experiment gets a GPS fix immediately outdoors
  
• The GPS tab in my custom experiment renders correctly (shows Latitude/Longitude/Altitude axes) — meaning phyphox parses the <location> block fine
  

What doesn't work

• The GPS graphs remain completely empty. No data points ever appear, even after 60+ seconds outside with a clear sky
  

Current XML (relevant excerpt)

Code:

<data-containers>     <container size="0" static="false">tGPS</container>     <container size="0" static="false">lat</container>     <container size="0" static="false">lon</container>     <container size="0" static="false">alt</container> </data-containers> <input>     <location>         <output component="lat">lat</output>         <output component="lon">lon</output>         <output component="altitude">alt</output>         <output component="time">tGPS</output>     </location>     <bluetooth name="BikeDetector" id="phyphoxBLE"               mode="notification" subscribeOnStart="true">         <output char="cddf1002-30f7-4671-8b43-5e40ba53514a"                 conversion="float32LittleEndian" offset="0">aX</output>         <!-- ... remaining channels ... -->         <output char="cddf1002-30f7-4671-8b43-5e40ba53514a"                 extra="time">t</output>     </bluetooth> </input>

Arduino loop (no poll, as recommended)

Code:

static const unsigned long SEND_INTERVAL_MS = 33; // ~30 Hz void loop() {     if (PhyphoxBLE::currentConnections == 0) {         delay(10);         return;     }     static unsigned long lastSend = 0;     unsigned long now = millis();     if (now - lastSend < SEND_INTERVAL_MS) return;     lastSend = now;     if (!IMU.accelerationAvailable() || !IMU.gyroscopeAvailable()) return;     float ax, ay, az, gx, gy, gz;     IMU.readAcceleration(ax, ay, az);     IMU.readGyroscope(gx, gy, gz);     PhyphoxBLE::write(ax, ay, az, gx, gy); }

Things I have already tried  

1. Location permission set to "While Using" with Precise Location enabled in iOS Settings
   
2. Testing outdoors with clear sky for 60+ seconds Swapping element order — putting <location> before <bluetooth> in the input block in case iOS initializes sensors in declaration order
   
3. Loading the experiment via a .phyphox file transferred by AirDrop instead of receiving the XML over BLE — in case file-loaded experiments initialize CLLocationManager differently than BLE-received ones 
   
4. Removing PhyphoxBLE::poll() from the loop entirely, as recommended in this thread 
   
5. Deleting and re-adding the experiment in phyphox to force a fresh XML fetch
   

In all cases: BLE IMU data works, GPS tab renders, GPS containers remain empty.  Is this a known iOS-specific limitation? The standalone Location experiment works fine, so location permission and hardware are not the issue — it seems specifically related to how the location manager is initialized in the context of a BLE experiment.