Goal

This is my dog Bogey

Bogey is a great dog, but he’s hard to find in my house. My next project is to track Bogey by putting a Bluetooth Low Energy (BLE) device on his collar. Using a Bluetooth receiver, like the one on a Raspberry Pi we can measure the relative signal strength of the BLE device to the receiver. An array of these receivers can resolve the floor and room of the house the device is. Because the relative signal strength of these devices has high variance, we will use machine learning techniques to improve the prediction of which room the device resides. I will then use the new Amazon Echo binding with openHAB 2.1 to allow me to ask my Echo where my dog is.

The goal of this post is to make sure your host’s Bluetooth receiver is working correctly and to install bluepy, a Python library that allows us to interface with Bluetooth programmatically.

What you need

• A Raspberry Pi with a Bluetooth adapter (A Raspberry Pi 3 Series B has one built in)
• A Bluetooth LE tracking device

Ensure the Bluetooth receiver is working

hcitool is used to configure Bluetooth connections and send some special command to Bluetooth devices. The first step is to verify the hcitool installation. You should see an entry like the following after running hcitool dev

pi@raspberrypi:~ $ hcitool dev
Devices:
    hci0    B8:27:EB:44:3A:DC

Then we will do a scan! The output is below. The first entry is the MAC address of the receiver. MAC addresses are for every device. The second column is the advertised name. Many devices do not identify themselves without pairing. Our BTLE devices will usually identify themselves with this scan. Here are I have three different devices. This scan will pick up not only BTLE devices. It will also pick up your phone if Bluetooth is on, as well as things like wireless keyboards and headphones.

 sudo hcitool lescan

 LE Scan ...
D0:B5:C2:CF:39:B1 E-Beacon_CF39B1
F1:47:8D:FF:EC:17 VSF
C8:A9:20:FE:BB:DC MiniBeacon_54301

Next we will install bluepy so we can get programmatic access to our Bluetooth receiver.

$ sudo apt-get install python-pip libglib2.0-dev
$ sudo pip install bluepy

We will now create a simple python program that will print out the Received signal strength indication (rssi), for all Bluetooth device addresses passed into it on the command line. We will name it btle_rssi.py. It spends 4.5 seconds scanning for devices.

import sys
import time

from bluepy.btle import Scanner, DefaultDelegate

class ScanDelegate(DefaultDelegate):
    def __init__(self):
        DefaultDelegate.__init__(self)

scanner = Scanner().withDelegate(ScanDelegate())
devices = scanner.scan(4.5)

deviceMap = {}

inputList = sys.argv[1:]
devNumber = 1

for deviceId in inputList:
    deviceMap[deviceId] = devNumber
    devNumber += 1

for dev in devices:
    for deviceId in inputList:
       if deviceId.lower() == dev.addr:
            print("rssi.device%d %d %d" % (deviceMap[deviceId], dev.rssi, time.time()))

To run it issue the following command. You can specify any number of mac_addresses with this program.

  sudo python btle_rssi.py [mac_address]

    >> rssi.device1 -42 1504584026

Congratulations! You can now do a Bluetooth scan and programmatically measure the rssi of any device within range.