I have a raspberry Pi 4B 4GB ram and I want to connect it to 16 Bluetooth oximeters(BLE) and take readings after every 20 secs.

Now I know that pi can connect to only 7-8 Bluetooth devices at a time so Can I use 2 USB Bluetooth adapters to connect to over 15 oximeters ?

If yes, is it a good solution?

If no, what else can I use/do?

  • Please keep it to one question!
    – MatsK
    May 21, 2021 at 14:12

1 Answer 1


In the Bluetooth spec there is no limit on the number of connections that can be made. However, in the real world, the Bluetooth hardware has constrained resources that have a practical limit to the number of simultaneous connections that can be maintained. By adding additional radios (USB dongles) then you should be able to raise the number of supported connections. There will be some overhead in your code to manage which dongle is connected to which oximeter but this should be relatively straight forward.

I would expect the BLE oximeters to share their readings via notifications. Maybe use a generic Bluetooth Low Energy scanning and exploration tool like nRF Connect to understand how the device is sharing its data

  • The only problem I can see here is how will I communicate with the oximeters through the bluetooth dongals. If I was using Pi's onboard bluetooth, I would've written python code to seach for required characteristics from the oximeter, but now instead of Pi being connected to the oximeter, the dongal is. How can I code the doncal to communicate with the oximeter? May 20, 2021 at 7:59
  • I am assuming you would use the BlueZ DBus API from within Python. To select which dongle you use will be controlled by the number in hci* part of the DBus path. More details can be found in the following answer: stackoverflow.com/a/63888028/7721752
    – ukBaz
    May 20, 2021 at 8:30

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