Bluetooth scanning

btWatcher.py

#!/usr/bin/python
# Huge thanks to:  https://github.com/blakeman399/Bluetooth-Proximity-Light/blob/master/https/github.com/blakeman399/Bluetooth-Proximity-Light.py


# This script scans the area looking for a list of devices with known Bluetooth
# MAC addresses.  Once seen, a notification is immediately sent to the Bomba
# system.  After that an occasional scan occurs to see if the device is still
# in the area, notifying when it is "missing" then again several minutes later
# when it still hasn't been seen and is certainly "gone".

import fcntl
import struct
import array
import bluetooth
import bluetooth._bluetooth as bt
import time
import os
import datetime

def bluetooth_rssi(addr):
	# Open hci socket
	hci_sock = bt.hci_open_dev()
	hci_fd = hci_sock.fileno()

	# Connect to device (to whatever you like)
	#
	# Original timeout was 10 seconds.  For some reason at 5 seconds
	# or less it goes wonky with non-present BT MACs
	bt_sock = bluetooth.BluetoothSocket(bluetooth.L2CAP)
	bt_sock.settimeout(3)
	result = bt_sock.connect_ex((addr, 1))	# PSM 1 - Service Discovery
	if result != 0:
		return -255	# failed to connect before timeout

	try:
		# Get ConnInfo
		reqstr = struct.pack("6sB17s", bt.str2ba(addr), bt.ACL_LINK, "\0" * 17)
		request = array.array("c", reqstr )
		handle = fcntl.ioctl(hci_fd, bt.HCIGETCONNINFO, request, 1)
		handle = struct.unpack("8xH14x", request.tostring())[0]

		# Get RSSI
		cmd_pkt=struct.pack('H', handle)
		rssi = bt.hci_send_req(hci_sock, bt.OGF_STATUS_PARAM,
					bt.OCF_READ_RSSI, bt.EVT_CMD_COMPLETE, 4, cmd_pkt)
		rssi = struct.unpack('b', rssi[3])[0]

		# Close sockets
		bt_sock.close()
		hci_sock.close()

		return rssi

	except:
		return -255

# This writes a file safely without worry of access
def AtomicWrite(path, text):
	tmppath = path + ".tmp"
	output = open(tmppath, "w")
	output.writelines(text)

	output.flush()
	os.fsync(output.fileno())
	output.close()
	os.rename(tmppath, path)	# atomic action

while True:

	mtime = 0
	if os.path.isfile("/media/ramdisk/user_MAC_IDs.txt"):
		mtime = os.path.getmtime("/media/ramdisk/user_MAC_IDs.txt")
		with open("/media/ramdisk/user_MAC_IDs.txt", "r") as f:
			newMACs = f.read().splitlines()

	newInArea = []
	newLastSeenInArea = []
	newRssi = []

	# Initialize the data structures for each MAC address.
	# Initially set all to far away
	for MAC in newMACs:
		try:
			iOldMAC = MACs.index(MAC)	# this will cause exception if not found
			newInArea.append(inArea[iOldMAC])
			newLastSeenInArea.append(lastSeenInArea[iOldMAC])
			newRssi.append(rssi[iOldMAC])
		except:
			# not found in existing data structure, so add with initial values
			newLastSeenInArea.append(0)
			newInArea.append(False)
			newRssi.append(-255)


	MACs = newMACs
	inArea = newInArea
	rssi = newRssi
	lastSeenInArea = newLastSeenInArea
	

	while True:
		if os.path.isfile("/media/ramdisk/user_MAC_IDs.txt") and mtime != os.path.getmtime("/media/ramdisk/user_MAC_IDs.txt"):
			print "Reloading MACs..."
			break		# break out of the loop to load/rebuild the structures

		print "Scanning..."
		seen = []			# MAC is visible
		missing = []		# MAC hasn't been seen in a bit
		gone = []			# MAC hasn't been seen for a long time

		for MAC in MACs:
			idx = MACs.index(MAC)

			# once seen, no need to rescan for device more than once
			# a minute.
			if inArea[idx] and time.time() - abs(lastSeenInArea[idx]) < 60:
				continue;

			# read new value
			rssi[idx] = bluetooth_rssi(MAC)

			# RSSI values have a high of zero and go down from there.  I.e.
			# higher is stronger.
			# 0 is almost certainly in the same room
			# Single digits (e.g. -5) is probably the same room, but I saw 0 to -6 from the room above (thru wood floors)
			# -10 to -19 could be same room or adjacent room (thru plaster walls)
			# -20 to -30 is probably in the house, but a distant room
			# -30 to -150 is very distant in the house
			# -255 is not seen at all (away from the house)

			# Values will certainly fluctuate even if the phone doesn't move.  For 
			# example, here are three subsequent readings from a CSR 4.0 module
			# without moving the phone:
			#                      Same room: 0 0 0 
			#                     Room above: -3 -4 -1
			#    Near room (plaster, stairs): -255 -19 -25
			# Near room (drywall, open door): -1 -6 -11
			#         Near room (2 drywalls): -16 -11 -6
			#	                Distant room: -25 -22 -26
			#	           Very distant room: -255 -27 -255
			strength = rssi[idx]

			print "Scan: [",idx,"]",MAC,"    strength=",strength

			if strength > -100:
				if not inArea[idx]:
					inArea[idx] = True
				lastSeenInArea[idx] = time.time()
				seen.append(MAC + " " + str(strength))
			else:
				# if not seen for 60 seconds, consider missing
				if inArea[idx] and lastSeenInArea[idx] > 0 and time.time() - lastSeenInArea[idx] >= 60:
					# negative time indicates that we've issued a 'missing' notice already
					lastSeenInArea[idx] = -lastSeenInArea[idx]
					print datetime.datetime.now(), "left the area: ", MAC
					missing.append(MAC)

				# if not seen for 5 minutes, consider gone
				if inArea[idx] and time.time() - abs(lastSeenInArea[idx]) >= 5*60:
					inArea[idx] = False
#					lastSeenInArea[idx] = 0
					print datetime.datetime.now(), "left the area: ", MAC
					gone.append(MAC)


		if seen:
			print "=== Seen: ",seen
			with open("/media/ramdisk/ipc/seen_bluetooth", "w") as f:
				f.writelines(seen)

		if missing:
			print "=== Missing: ",missing
			with open("/media/ramdisk/ipc/missing_bluetooth", "w") as f:
				f.writelines(missing)

		if gone:
			print "=== Has left: ",gone
			with open("/media/ramdisk/ipc/depart_bluetooth", "w") as f:
				f.writelines(gone)

		time.sleep(1)	# prevent rapid spinning if no MAC IDs