a star is born

README.md

@@ -0,0 +1,21 @@
+pyrtlsdr-peakfinder
+==============
+
+The quickest, dirtiest scanner imaginable to spit out frequencies on which signal peaks are detected for RTL-SDR radios. It is probably not very efficient, but it does work. For my hardware. Good luck.
+
+Usage: `peakfinder.py 88.0 110.0` (in megahertz)
+
+The values in the script were empirically determined and you should feel free to adjust them. Reported frequencies may lean slightly right of the signal's center.
+
+Copyright © 2013 Melissa Elliott (0xabad1dea)
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
+
+- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
+- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
+- Neither the name of the software nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
+
+![Secret fourth clause: more Kasane Teto](http://i.imgur.com/Ikzrr4Q.png)
+
+[image source](http://seiga.nicovideo.jp/seiga/im1354345)

peakfinder.py

@@ -0,0 +1,134 @@
+#! /usr/bin/python
+# quick and dirty peakfinder for RTL-SDR by 0xabad1dea
+# scans a range and reports signals found in mhz
+
+# Tries very hard to not report those !@#$ phantom lines ---
+# but as a result, avoid centering the window exactly on a
+# frequency if you're specifically looking for it, as it may
+# disappear or split into two.
+
+# probably not very efficient
+
+# BSD three-clause
+
+# depends: https://github.com/roger-/pyrtlsdr
+
+
+# fixme: narrow down the import... 
+from pylab import *
+from rtlsdr import *
+
+sdr = RtlSdr()
+
+# configure device
+sdr.sample_rate = 2.4e6
+# lower the gain to, like, 4 if you don't want to hear about weak signals
+sdr.gain = 19
+
+	
+########################################################################
+def peakdet(v, delta, x = None):
+# hacked up from https://gist.github.com/endolith/250860
+    maxtab = []
+           
+    if x is None:
+        x = arange(len(v))
+    
+    v = asarray(v)
+    
+    mn, mx = Inf, -Inf
+    mnpos, mxpos = NaN, NaN
+    
+    lookformax = True
+    
+    for i in arange(len(v)):
+        this = v[i]
+        if this > mx:
+            mx = this
+            mxpos = x[i]
+        if this < mn:
+            mn = this
+            mnpos = x[i]
+        
+        if lookformax:
+            if this < mx-delta:
+                maxtab.append((mxpos, mx))
+                mn = this
+                mnpos = x[i]
+                lookformax = False
+        else:
+            if this > mn+delta:
+                mx = this
+                mxpos = x[i]
+                lookformax = True
+ 
+    return array(maxtab)
+
+########################################################################
+
+def findsignals(candidates):
+# input and output as [ [strength, strength, strength], [freq, freq, freq] ]
+	sigdelta = 0.08 # adjacent peaks closer than this are collated
+
+	# remove the center false spike before analysis
+	cf = sdr.center_freq / 1e6
+
+	# there's probably a more pythonic way to do this
+	# but I'm just a humble C programmer
+	for i in range(len(candidates[1])):
+		if candidates[1][i] > (cf - (sigdelta/2)) and candidates[1][i] < (cf + (sigdelta/2)) :
+			candidates[0][i] = 0.0
+			
+	# find local peaks
+	max = peakdet(candidates[0],.0001) # empirical - adjust as desired
+	# (make it smaller if you're looking for faint, wide signals)
+
+	signals = []
+	prevfreq = 0.0
+
+	# collate adjacent peaks
+	for i in max:
+		if candidates[1][i[0]] - prevfreq < sigdelta:
+			# leans right rather than left
+			# (a cool person would perfectly center it?)
+			del(signals[-1])
+		signals.append([i[1], candidates[1][i[0]]])
+		prevfreq = candidates[1][i[0]]
+		
+	return signals
+		
+########################################################################
+
+signals = []
+
+if len(sys.argv) != 3:
+	exit("usage: peakfinder.py 88.0 110.0")
+
+start = float(sys.argv[1])
+end = float(sys.argv[2])
+if start <= 0 or end <= 0:
+	exit("error: bad arguments")
+
+if end < start:
+	exit("error: end < start")
+
+freq = start
+
+while(freq <= end):
+	sdr.center_freq = freq * 1e6
+	freq += 2.2 # this number was picked empirically to avoid overlap on my device
+	samples = sdr.read_samples(256*1024)
+	# plot the spectrum
+	results = psd(samples, NFFT=1024, Fs=sdr.sample_rate/1e6, Fc=sdr.center_freq/1e6)
+
+	signals.extend(findsignals(results))
+	
+
+# print just the frequency part 
+print "++++++++++"
+for i in signals:
+	print "%.2f" % i[1]
+print "++++++++++"
+
+
+