How to get the BLE data to build my own app?

[alexhoopes]

I'm working on my own iOS app that tracks 0-60 times and location data. I'm just getting started and was wondering how I can interface with the BLE on this? Does anyone have any direction in what I need to learn to be able to pull the NMEA sentences off via BLE? I'll be able to parse all the data after that, I just can't figure out how to interface with it and receive the sentences.
Thanks!

Edit: I tried looking at the data from a BLE discovery app in the Location and Navigation service but it shows no data. Not sure if I'm looking in the wrong place

I also see that nothing is being printed on serial in terms of NMEA sentences, is that supposed to be the case?

I've also tried the following Python to try and read the BLE data but nothing gets printed:

import asyncio
from bleak import BleakClient, BleakScanner

# Constants from the BonoGPS code
LOCATION_SERVICE_UUID = "00001819-0000-1000-8000-00805f9b34fb"  # 0x1819 SERVICE_LOCATION_AND_NAVIGATION
LOCATION_CHAR_UUID = "00002A67-0000-1000-8000-00805f9b34fb"    # 0x2A67 LOCATION_AND_SPEED
DEVICE_NAME_PREFIX = "BonoGPS"

async def notification_handler(sender, data):
    """Print raw data from the GPS device"""
    print(f"\nRaw bytes: {data}")
    try:
        # Try to decode as ASCII and print
        ascii_data = data.decode('ascii')
        print(f"ASCII decoded: {ascii_data}")
    except UnicodeDecodeError:
        print("Could not decode as ASCII")
    print("-" * 50)

async def scan_for_device():
    print("Scanning for BonoGPS devices...")
    devices = await BleakScanner.discover()
    
    for device in devices:
        if device.name and DEVICE_NAME_PREFIX in device.name:
            print(f"Found BonoGPS device: {device.name} ({device.address})")
            return device
            
    print("No BonoGPS devices found!")
    return None

async def main():
    try:
        # Scan for device
        device = await scan_for_device()
        if not device:
            return

        print(f"\nConnecting to {device.name}...")
        async with BleakClient(device.address) as client:
            print("Connected!")
            
            # Print services and characteristics for debugging
            print("\nAvailable services:")
            for service in client.services:
                print(f"Service: {service.uuid}")
                for char in service.characteristics:
                    print(f"  Characteristic: {char.uuid}")
                    print(f"    Properties: {char.properties}")
            
            print("\nStarting notifications...")
            await client.start_notify(LOCATION_CHAR_UUID, notification_handler)
            
            print("\nReceiving raw data (Press Ctrl+C to stop)...")
            while True:
                await asyncio.sleep(0.1)

    except KeyboardInterrupt:
        print("\nStopping...")
    except Exception as e:
        print(f"Error: {e}")

if __name__ == "__main__":
    asyncio.run(main())

No data is coming through

@renatobo, any chance I could get some insight here? Thanks for this amazing program by the way :)

[alexhoopes]

It seems the GPIO pins were configured wrong and that's why I wasn't getting data. Fixed it! Time to make the app, still, thank you for this program !!

[alexhoopes]

Or maybe not, it was working but after a reboot not anymore... serial log is showing BLE buffer saturated, resetting being spammed over and over

[renatobo]

I recommend you get things up and running at 1Hz, with one of the applications I list in the documentation.
Once you know your GPS and esp32 are working correctly, you should build your app.

Also, before building an app that reads GPS data, try broadcasting a simple message with a serial counter and have it read on your app.

Develop and test each step below separately

• GPS -> esp32
• esp32 to BLE stack
• BLE stack to iOS BLE stack
• BLE stack on iOS to app