Detecting Smartphone via Bluetooth on Linux (Raspberry Pi 2)

First of all you need a Bluetooth USB dongle. I buyed the Logilink BT00015 (available at amazon.com, amazon.de or elsewhere). I would expect that others work, too. But as always: On Linux, drivers can be tricky and it's always good to know working hardware.

Before installing drivers it is always a good idea to update everything:

sudo apt-get update
sudo apt-get upgrade

Then install the libraries needed for bluetooth

sudo apt-get install --no-install-recommends bluetooth

I received an error that some dependencies could not be resolved. I fixed that by entering the following commands:

sudo dpkg --configure -a
sudo apt-get install -f

Now insert the USB dongle and restart the raspberry

sudo shutdown -r now

To check if the USB-dongle is detected,  enter the following command:

lsusb

This lists all USB devices. There should be one offering Bluetooth - services

Now lets check if the Bluetooth itself works:

/etc/init.d/bluetooth status

The response should now contain the word "Running":

pi@raspberrypi:~ $ /etc/init.d/bluetooth status
● bluetooth.service - Bluetooth service
 Loaded: loaded (/lib/systemd/system/bluetooth.service; enabled)
 Active: active (running) since Sat 2016-02-27 19:31:45 UTC; 17min ago
 Docs: man:bluetoothd(8)
 Main PID: 7841 (bluetoothd)
 Status: "Running"
 CGroup: /system.slice/bluetooth.service
 └─7841 /usr/lib/bluetooth/bluetoothd

Now it's time to check for devices. Do nothing with your phone right now and enter:

hcitool scan

This should display all Bluetooth-devices in Range. As you haven't done anything with your phone yet it should not be displayed there. The output should be something like this:

Scanning ...
 7C:2F:BE:EF:FA:CE Ole
 00:04:BE:EF:FA:CE SHIELD
 B8:86:BE:EF:FA:CE Fette Glotze
 88:53:BE:EF:FA:CE TOMATO-PC
 48:44:BE:EF:FA:CE TVBluetooth

(I modified the MAC addresses. I am not absolutely sure if anyone could do evil things using the MACs, but I prefer not to find that out :) )

Now put your phone into discovery mode. On Android Marshmallow you just have to enter your Bluetooth-settings for this. Then re-scan your devices. There should be one more, now:

hcitool scan

7C:2F:BE:EF:FA:CE Ole
00:04:BE:EF:FA:CE SHIELD
B8:86:BE:EF:FA:CE Fette Glotze
88:53:BE:EF:FA:CE TOMATO-PC
48:44:BE:EF:FA:CE TVBluetooth

F8:95:C7:H0:0H:0H G4

Now just note your Mac-Address. We will not pair our device. That takes a few steps and additional packages and additional problems. Pairing is not needed once we know the mac-address.

Now we cam just check the presence by using the info command. Simply leave your Bluetooth-settings on the phone and enter

sudo hcitool info F8:95:C7:H0:0H:0H

Event though your phone isn't in discovery-mode anymore you will get some status information like the device name:

Requesting information ...
 BD Address: F8:95:C7:H0:0H:0H
 Device Name: G4
 LMP Version: 4.1 (0x7) LMP Subversion: 0x6109
 Manufacturer: Broadcom Corporation (15)

if you turn off Bluetooth on your phone and re-enter that command you will receive a different response:

Requesting information ...
Can't create connection: Input/output error

So that's it. Just use the good old grep in your bash-script to check whether the phone is there or not:

if hcitool info F8:95:C7:H0:0H:0H | grep -q 'Device Name'; then
 // Do whatever you like if you found it
fi

Again: Have fun :)