debug wierd constellation results due to bad indexing

common.py

@@ -7,7 +7,7 @@ log = logging.getLogger(__name__)
 Fs = 32e3
 Ts = 1.0 / Fs
 
-frequencies = (np.arange(10) + 1) * 1e3
+frequencies = (1 + np.arange(1)) * 1e3
 carrier_index = 0
 Fc = frequencies[carrier_index]
 Tc = 1.0 / Fc

loop.py

@@ -22,14 +22,8 @@ class Filter(object):
 
 
 class FreqLoop(object):
-    def __init__(self, x, freqs, prefix=0.0):
+    def __init__(self, src, freqs):
         interp = sampling.Interpolator()
-        if prefix is None:
-            prefix = []
-        else:
-            prefix = [prefix] * (interp.width - 1)
-
-        src = itertools.chain(prefix, x)
         self.sampler = sampling.Sampler(src, interp)
         self.gens = []
 

sampling.py

@@ -1,4 +1,5 @@
 import numpy as np
+import itertools
 import logging
 
 log = logging.getLogger(__name__)
@@ -32,12 +33,14 @@ class Interpolator(object):
 
 class Sampler(object):
     def __init__(self, src, interp=None):
-        self.src = iter(src)
         self.freq = 1.0
         self.interp = interp if (interp is not None) else Interpolator()
-        coeffs, begin = self.interp.get(0)
-        self.offset = -begin  # should fill samples buffer
-        self.buff = np.zeros(len(coeffs))
+
+        # TODO: explain indices arithmetic
+        padding = [0.0] * (self.interp.width - 1)
+        self.src = itertools.chain(padding, src)
+        self.offset = self.interp.width + 1
+        self.buff = np.zeros(self.interp.coeff_len)
         self.index = 0
 
     def __iter__(self):

test.sh

@@ -2,7 +2,7 @@
 set -u 
 set -e 
 
-dd if=/dev/urandom of=data.send bs=1024 count=16
+dd if=/dev/urandom of=data.send bs=128 count=1 status=none
 ./send.py tx.int16
 
 killall arecord aplay || true