mirror of
https://github.com/romanz/amodem.git
synced 2026-02-08 18:38:01 +08:00
88 lines
1.9 KiB
Python
88 lines
1.9 KiB
Python
import cStringIO
|
|
import numpy as np
|
|
|
|
import logging
|
|
log = logging.getLogger(__name__)
|
|
|
|
Fs = 32e3
|
|
Ts = 1.0 / Fs
|
|
|
|
frequencies = (np.arange(4) + 8) * 1e3
|
|
carrier_index = len(frequencies)/2
|
|
Fc = frequencies[carrier_index]
|
|
Tc = 1.0 / Fc
|
|
|
|
Tsym = 1e-3
|
|
Nsym = int(Tsym / Ts)
|
|
baud = int(1/Tsym)
|
|
|
|
scaling = 32000.0 # out of 2**15
|
|
SATURATION_THRESHOLD = 1.0
|
|
|
|
LENGTH_FORMAT = '<I'
|
|
|
|
def to_bits(bytes_list):
|
|
for val in bytes_list:
|
|
for i in range(8):
|
|
mask = 1 << i
|
|
yield (1 if (val & mask) else 0)
|
|
|
|
bit_weights = [1 << i for i in range(8)]
|
|
def to_byte(bits):
|
|
assert len(bits) == 8
|
|
byte = int(np.dot(bits, bit_weights))
|
|
return chr(byte)
|
|
|
|
def load(fileobj):
|
|
return loads(fileobj.read())
|
|
|
|
def loads(data):
|
|
x = np.fromstring(data, dtype='int16')
|
|
x = x / scaling
|
|
t = np.arange(len(x)) / Fs
|
|
return t, x
|
|
|
|
def dumps(sym, n=1):
|
|
sym = sym.imag * scaling
|
|
sym = sym.astype('int16')
|
|
data = sym.tostring()
|
|
return data * n
|
|
|
|
def norm(x):
|
|
return np.sqrt(np.dot(x.conj(), x).real)
|
|
|
|
|
|
def iterate(data, bufsize, offset=0, advance=1, func=None):
|
|
assert bufsize > 0
|
|
assert offset >= 0
|
|
assert advance > 0
|
|
buf = np.zeros(bufsize)
|
|
buf_index = 0
|
|
for data_index, value in enumerate(data):
|
|
if data_index < offset:
|
|
continue
|
|
|
|
buf[buf_index] = value
|
|
buf_index += 1
|
|
|
|
if buf_index == bufsize:
|
|
result = func(buf) if func else buf
|
|
yield offset, result
|
|
buf[:-advance] = buf[advance:]
|
|
buf_index = max(0, buf_index - advance)
|
|
offset += advance
|
|
|
|
if __name__ == '__main__':
|
|
|
|
import pylab
|
|
def plot(f):
|
|
t = pylab.linspace(0, Tsym, 1e3)
|
|
x = pylab.sin(2 * pylab.pi * f * t)
|
|
pylab.plot(t / Tsym, x)
|
|
t = pylab.linspace(0, Tsym, Nsym + 1)
|
|
x = pylab.sin(2 * pylab.pi * f * t)
|
|
pylab.plot(t / Tsym, x, '.k')
|
|
|
|
plot(Fc)
|
|
pylab.show()
|