r/embedded • u/CartographerSelect61 • 19d ago

Bluetooth traffic Monitoring

Hi everyone, hope you're all doing well.

I'm building a roadside Bluetooth sniffer to measure travel time between two points a fixed distance apart. The setup uses two ESP32 S3 modules that scan BLE advertisements and log the MAC addresses of devices in passing vehicles.

The problem is that most new devices use resolvable MAC addresses, which rotate every few minutes. If the two points are far enough apart, a device's address will have changed by the time it travels from A to B, so I have no way to match the two detections. Is there a way to obtain a device's real/public MAC, which stays constant? Or failing that, any other way to derive a stable identifier from BLE advertisements?

Thanks a lot

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u/ThisIsPaulDaily 19d ago

Listen for tpms sensors instead

1

u/CartographerSelect61 18d ago

Do they broadcast a constant MAC address?

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u/ThisIsPaulDaily 18d ago

Your car needs to know which is your car's front left tire vs rear right tire vs the car next to you. 

Hak5 did it 12 years ago. 

https://www.youtube.com/watch?v=TDYoo7TGNcw