dominicgs · March 3, 2016 22:10 · Mar 3, 2016
diff --git a/piconet.py b/piconet.py
@@ -0,0 +1,118 @@
+#!/usr/bin/env python
+
+# Copyright 2016 Dominic Spill, Michael Ossmann, Will Code
+
+BT_NUM_CHANNELS = 79
+
+class Piconet(object):
+	def __init__(self, address):
+		self.address = address
+		self.sequence = []
+		self.precalc()
+		self.perm_table_init()
+		self.gen_hops()
+
+	# do all the precalculation that can be done before knowing the address
+	def precalc(self):
+		# populate channel list
+		# actual frequency is 2402 + channel[i] MHz
+		self.channels = [
+			(i * 2) % BT_NUM_CHANNELS
+			for i in xrange(BT_NUM_CHANNELS)
+		]
+
+
+		# precalculate some of single_hop()/gen_hop()'s variables
+		self.a1 = (self.address >> 23) & 0x1f
+		self.b = (self.address >> 19) & 0x0f
+		self.c1 = ((self.address >> 4) & 0x10) + \
+			((self.address >> 3) & 0x08) + \
+			((self.address >> 2) & 0x04) + \
+			((self.address >> 1) & 0x02) + \
+			(self.address & 0x01)
+		self.d1 = (self.address >> 10) & 0x1ff
+		self.e = ((self.address >> 7) & 0x40) + \
+			((self.address >> 6) & 0x20) + \
+			((self.address >> 5) & 0x10) + \
+			((self.address >> 4) & 0x08) + \
+			((self.address >> 3) & 0x04) + \
+			((self.address >> 2) & 0x02) + \
+			((self.address >> 1) & 0x01)
+
+	# 5 bit permutation
+	# assumes z is constrained to 5 bits, p_high to 5 bits, p_low to 9 bits
+	def perm5(self, z, p_high, p_low):
+		index1 = (0, 2, 1, 3, 0, 1, 0, 3, 1, 0, 2, 1, 0, 1)
+		index2 = (1, 3, 2, 4, 4, 3, 2, 4, 4, 3, 4, 3, 3, 2)
+
+		# bits of p_low and p_high are control signals
+		p = [(p_low >> i) & 0x01 for i in xrange(9)]
+		p.extend([(p_high >> i) & 0x01 for i in xrange(5)])
+
+		# bit swapping will be easier with an array of bits
+		z_bit = [(z >> i) & 0x01 for i in xrange(5)]
+
+
+		# butterfly operations
+		for i in xrange(13, 0, -1):
+			# swap bits according to index arrays if control signal tells us to
+			if (p[i]):
+				tmp = z_bit[index1[i]]
+				z_bit[index1[i]] = z_bit[index2[i]]
+				z_bit[index2[i]] = tmp
+
+		# reconstruct output from rearranged bits
+		output = sum([z_bit[i] << i for i in xrange(5)])
+		return output
+
+	def perm_table_init(self):
+		# populate perm_table for all possible inputs
+		self.perm_table = [[[self.perm5(z, p_high, p_low) for p_low in xrange(0x200)]for p_high in xrange(0x20)] for z in xrange(0x20)]
+
+	# drop-in replacement for perm5() using lookup table
+	def fast_perm(self, z, p_high, p_low):
+		return self.perm_table[z][p_high][p_low]
+
+	# generate the complete hopping sequence
+	def gen_hops(self):
+		# a, b, c, d, e, f, x, y1, y2 are variable names used in section 2.6 of the spec
+		# sequence index = clock >> 1
+		f = base_f = 0
+		for h in xrange(0x04):
+			#clock bits
+			for i in xrange(0x20):
+				# clock bits 21-25
+				a = self.a1 ^ i
+				for j in xrange(0x20):
+					# clock bits 16-20
+					c = self.c1 ^ j
+					c_flipped = c ^ 0x1f
+					for k in xrange(0x200):
+						# clock bits 7-15
+						d = self.d1 ^ k
+						for x in xrange(0x20):
+							# clock bits 2-6
+							perm_in = ((x + a) % 32) ^ self.b
+							# y1 (clock bit 1) = 0, y2 = 0
+							perm_out = self.fast_perm(perm_in, c, d)
+							channel = self.channels[(perm_out + self.e + f) % BT_NUM_CHANNELS]
+							self.sequence.append(channel)
+
+							# y1 (clock bit 1) = 1, y2 = 32
+							perm_out = self.fast_perm(perm_in, c_flipped, d)
+							channel = self.channels[(perm_out + self.e + f + 32) % BT_NUM_CHANNELS]
+							self.sequence.append(channel)
+						base_f = base_f + 16
+						f = base_f % BT_NUM_CHANNELS
+						if len(self.sequence) > 20:
+							return
+
+if __name__ == '__main__':
+	import sys
+	if len(sys.argv) < 2:
+		print "Using default address of 00:00:65:87:CB:A9"
+		address = 0x6587cba9
+	else:
+		address = int(sys.argv[1].replace(':',''), 16)
+	pn = Piconet(address)
+	print pn.sequence[:20]
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