fix drift correction demo

drift.py

@@ -2,43 +2,22 @@ import numpy as np
 import pylab
 
 import common
-import sigproc
 import loop
 
-def main():
-    f0 = 10e3
-    _, x = common.load(file('recv_10kHz.pcm', 'rb'))
-    x = x[100:]
+t = np.arange(0.1*common.Fs) * common.Ts
+f = common.Fc * (1 + 10e-6)
+x = np.sin(2*np.pi*f*t)
+fl = loop.FreqLoop(iter(x), [common.Fc])
 
-    S = []
-    Y = []
+S = []
+gain = common.Nsym / (2*np.pi)
+for s, in fl:
+    y = np.round(s)
+    if abs(y) > 0:
+        err = -np.angle(s / y) * gain
+        S.append([err])
+        fl.sampler.offset += 0.5*err
 
-    prefix = 100
-    symbols = loop.FreqLoop(x, [f0])
-    for s, in symbols:
-        S.append(s)
-        if len(S) > prefix:
-            symbols.correct(s, np.mean(S[:prefix]))
-        Y.append([
-            symbols.correction * (f0 / common.Nsym),
-        ])
-
-    S = np.array(S)
-
-    pylab.figure()
-
-    pylab.subplot(121)
-    circle = np.exp(2j*np.pi*np.linspace(0, 1, 1001))
-    pylab.plot(S.real, S.imag, '.', circle.real, circle.imag, ':')
-    pylab.grid('on')
-    pylab.axis('equal')
-
-    Y = np.array(Y)
-    a = 0.01
-    pylab.subplot(122)
-    pylab.plot(list(sigproc.lfilter([a], [1, a-1], Y)), '-')
-    pylab.grid('on')
-
-if __name__ == '__main__':
-    main()
-    pylab.show()
+S = np.array(S)
+pylab.plot(S)
+pylab.show()