class Demod:
SAMP_RATE = 256000.
SAMP_WINDOW = 1024*40
def __init__(self):
self.sdr = RtlSdr()
# Sampling rate
self.sdr.rs = Demod.SAMP_RATE
# Pins 1 and 2
self.sdr.set_direct_sampling(1)
# I don't think this is used?
self.sdr.gain = 1
def run(self, limit=None, callback=lambda x: print(x),
carrier=32000, bw=1000, sps=8,
codes=manchester, mod=Mods.MAGNITUDE,
header=HEADER, footer=FOOTER, pktlen=PKTBYTES):
# Center frequency
self.sdr.fc = carrier
self.mod = mod
self.header = header
self.footer = footer
self.pktlen = 8*pktlen + len(footer)
self.rxcallback = callback
decim = Demod.SAMP_RATE/bw/sps
assert decim == int(decim)
self.decim = int(decim)
assert Demod.SAMP_WINDOW % self.decim == 0
self.sampchips = Demod.SAMP_WINDOW / self.decim
self.corr = codes2corr(codes, sps)
self.codelen = len(self.corr[0])
self.last = np.zeros(Demod.SAMP_WINDOW)
self.index = 0
self.tocheck = [None] * self.codelen
for i in range(self.codelen):
self.tocheck[i] = dict()
self.tocheck[i]['last'] = ''.join(range(0))
self.tocheck[i]['pkts'] = range(0)
if limit is None:
def byte_callback(samp, sdr):
if select.select([sys.stdin], [], [], 0)[0]:
sdr.cancel_read_async()
self.ddc(samp, sdr)
else:
@limit_calls(limit)
def byte_callback(samp, sdr):
if select.select([sys.stdin], [], [], 0)[0]:
sdr.cancel_read_async()
self.ddc(samp, sdr)
self.sdr.read_bytes_async(byte_callback, Demod.SAMP_WINDOW*2)
print (self.index, "samples read")
sys.stdout.flush()
sys.stdin.readline()
def bb2c(self, baseband):
mag = np.abs(baseband)
phase = np.angle(baseband)
dp = np.mod(np.ediff1d(phase)+np.pi, 2*np.pi)-np.pi
return mag[1:], phase[1:], dp
def decode(self, chips):
corrs = []
for c in self.corr:
corrs.append(np.correlate(chips, c))
# Vector correlations
if np.iscomplex(corrs).any():
corrs = np.abs(corrs)
maxes = np.max(np.array(corrs), 0)
codes = np.argmax(np.array(corrs), 0)
return maxes, codes
def debounce(self, i, l, rxstr):
try:
if i != self.debounce_i or abs(l - self.debounce_l) > 1:
self.rxcallback(rxstr)
except AttributeError:
self.rxcallback(rxstr)
self.debounce_i = i
self.debounce_l = l
def extract(self, nc):
for codeoffset in range(self.codelen):
pkts = []
codestr = "".join(map(repr, map(int, nc[codeoffset::self.codelen])))
for p in self.tocheck[codeoffset]['pkts']:
pkt = p + codestr[0:self.pktlen-len(p)]
if len(pkt) < self.pktlen:
pkts.append(pkt)
elif len(self.footer) == 0 or pkt[-len(self.footer):] == self.footer:
str = ""
for j in range(0,len(pkt)-1,8):
str += chr(int(pkt[j:j+8][::-1], 2))
self.debounce(self.index, -len(p), str)
sys.stdout.flush()
codestr = self.tocheck[codeoffset]['last'] + codestr
for ind in find_all(codestr, self.header):
pkt = codestr[ind+len(self.header):ind+len(self.header)+self.pktlen]
if len(pkt) < self.pktlen:
pkts.append(pkt)
elif len(self.footer) == 0 or pkt[-len(self.footer):] == self.footer:
str = ""
for j in range(0,len(pkt)-1,8):
str += chr(int(pkt[j:j+8][::-1], 2))
self.debounce(self.index, ind, str)
sys.stdout.flush()
self.tocheck[codeoffset]['pkts'] = [] + pkts
self.tocheck[codeoffset]['last'] = "" + codestr[-len(self.header)+1:]
def ddc(self, samp, sdr):
s = np.asarray(samp)
i, q = s[::2], s[1::2]
i = np.mean(i.reshape(-1,self.decim), 1) # poor man's decimation
q = np.mean(q.reshape(-1,self.decim), 1) # poor man's decimation
iq = np.empty(len(i), 'complex')
iq.real, iq.imag = i, q
iq /= (255/2)
iq -= (1 + 1j)
baseband = np.concatenate((self.last, iq))
self.last = iq
mag, phase, dp = self.bb2c(baseband)
if self.mod == Mods.MAGNITUDE:
sig = mag
elif self.mod == Mods.PHASE:
sig = phase
elif self.mod == Mods.DPHASE:
sig = dp
else:
sig = baseband
corrs, codes = self.decode(sig)
nc = codes[self.codelen:self.codelen+self.sampchips]
self.extract(nc)
self.index += 1
def end(self):
self.sdr.close()
def plot(self):
plt.ion()
fig = plt.figure()
ax1 = fig.add_subplot(311)
ax1.plot(self.chips)
ax2 = fig.add_subplot(312, sharex=ax1)
ax2.plot(self.corrs)
ax3 = fig.add_subplot(313, sharex=ax1)
ax3.plot(self.demod)
plt.show()
def checkdemod(self, index, demod=None, packetlen=5):
if demod is None:
demod = self.demod
l = packetlen*8+6+7
b = self.demod[index:index+l*self.codelen:self.codelen]
return chipsToString(np.concatenate(([1,0], b, [0])))
def findstring(self, demod = None, packetlen=5):
if demod is None:
demod = self.demod
find = []
for i in range(len(demod)):
s, c = self.checkdemod(i, demod, packetlen)
if len(s) and s[0] == 'a' and s[-1] == 'x':
find.append((i, s[1:-1]))
return find
class Demod:
SAMP_RATE = 256000.
SAMP_WINDOW = 1024 * 40
def __init__(self):
self.sdr = RtlSdr()
# Sampling rate
self.sdr.rs = Demod.SAMP_RATE
# Pins 1 and 2
self.sdr.set_direct_sampling(1)
# I don't think this is used?
self.sdr.gain = 1
def run(self,
limit=None,
callback=lambda x: print(x),
carrier=32000,
bw=1000,
sps=8,
codes=manchester,
mod=Mods.MAGNITUDE,
header=HEADER,
footer=FOOTER,
pktlen=PKTBYTES):
# Center frequency
self.sdr.fc = carrier
self.mod = mod
self.header = header
self.footer = footer
self.pktlen = 8 * pktlen + len(footer)
self.rxcallback = callback
decim = Demod.SAMP_RATE / bw / sps
assert decim == int(decim)
self.decim = int(decim)
assert Demod.SAMP_WINDOW % self.decim == 0
self.sampchips = Demod.SAMP_WINDOW / self.decim
self.corr = codes2corr(codes, sps)
self.codelen = len(self.corr[0])
self.last = np.zeros(Demod.SAMP_WINDOW)
self.index = 0
self.tocheck = [None] * self.codelen
for i in range(self.codelen):
self.tocheck[i] = dict()
self.tocheck[i]['last'] = ''.join(range(0))
self.tocheck[i]['pkts'] = range(0)
if limit is None:
def byte_callback(samp, sdr):
if select.select([sys.stdin], [], [], 0)[0]:
sdr.cancel_read_async()
self.ddc(samp, sdr)
else:
@limit_calls(limit)
def byte_callback(samp, sdr):
if select.select([sys.stdin], [], [], 0)[0]:
sdr.cancel_read_async()
self.ddc(samp, sdr)
self.sdr.read_bytes_async(byte_callback, Demod.SAMP_WINDOW * 2)
print(self.index, "samples read")
sys.stdout.flush()
sys.stdin.readline()
def bb2c(self, baseband):
mag = np.abs(baseband)
phase = np.angle(baseband)
dp = np.mod(np.ediff1d(phase) + np.pi, 2 * np.pi) - np.pi
return mag[1:], phase[1:], dp
def decode(self, chips):
corrs = []
for c in self.corr:
corrs.append(np.correlate(chips, c))
# Vector correlations
if np.iscomplex(corrs).any():
corrs = np.abs(corrs)
maxes = np.max(np.array(corrs), 0)
codes = np.argmax(np.array(corrs), 0)
return maxes, codes
def debounce(self, i, l, rxstr):
try:
if i != self.debounce_i or abs(l - self.debounce_l) > 1:
self.rxcallback(rxstr)
except AttributeError:
self.rxcallback(rxstr)
self.debounce_i = i
self.debounce_l = l
def extract(self, nc):
for codeoffset in range(self.codelen):
pkts = []
codestr = "".join(map(repr, map(int,
nc[codeoffset::self.codelen])))
for p in self.tocheck[codeoffset]['pkts']:
pkt = p + codestr[0:self.pktlen - len(p)]
if len(pkt) < self.pktlen:
pkts.append(pkt)
elif len(self.footer
) == 0 or pkt[-len(self.footer):] == self.footer:
str = ""
for j in range(0, len(pkt) - 1, 8):
str += chr(int(pkt[j:j + 8][::-1], 2))
self.debounce(self.index, -len(p), str)
sys.stdout.flush()
codestr = self.tocheck[codeoffset]['last'] + codestr
for ind in find_all(codestr, self.header):
pkt = codestr[ind + len(self.header):ind + len(self.header) +
self.pktlen]
if len(pkt) < self.pktlen:
pkts.append(pkt)
elif len(self.footer
) == 0 or pkt[-len(self.footer):] == self.footer:
str = ""
for j in range(0, len(pkt) - 1, 8):
str += chr(int(pkt[j:j + 8][::-1], 2))
self.debounce(self.index, ind, str)
sys.stdout.flush()
self.tocheck[codeoffset]['pkts'] = [] + pkts
self.tocheck[codeoffset]['last'] = "" + codestr[-len(self.header) +
1:]
def ddc(self, samp, sdr):
s = np.asarray(samp)
i, q = s[::2], s[1::2]
i = np.mean(i.reshape(-1, self.decim), 1) # poor man's decimation
q = np.mean(q.reshape(-1, self.decim), 1) # poor man's decimation
iq = np.empty(len(i), 'complex')
iq.real, iq.imag = i, q
iq /= (255 / 2)
iq -= (1 + 1j)
baseband = np.concatenate((self.last, iq))
self.last = iq
mag, phase, dp = self.bb2c(baseband)
if self.mod == Mods.MAGNITUDE:
sig = mag
elif self.mod == Mods.PHASE:
sig = phase
elif self.mod == Mods.DPHASE:
sig = dp
else:
sig = baseband
corrs, codes = self.decode(sig)
nc = codes[self.codelen:self.codelen + self.sampchips]
self.extract(nc)
self.index += 1
def end(self):
self.sdr.close()
def plot(self):
plt.ion()
fig = plt.figure()
ax1 = fig.add_subplot(311)
ax1.plot(self.chips)
ax2 = fig.add_subplot(312, sharex=ax1)
ax2.plot(self.corrs)
ax3 = fig.add_subplot(313, sharex=ax1)
ax3.plot(self.demod)
plt.show()
def checkdemod(self, index, demod=None, packetlen=5):
if demod is None:
demod = self.demod
l = packetlen * 8 + 6 + 7
b = self.demod[index:index + l * self.codelen:self.codelen]
return chipsToString(np.concatenate(([1, 0], b, [0])))
def findstring(self, demod=None, packetlen=5):
if demod is None:
demod = self.demod
find = []
for i in range(len(demod)):
s, c = self.checkdemod(i, demod, packetlen)
if len(s) and s[0] == 'a' and s[-1] == 'x':
find.append((i, s[1:-1]))
return find
