Browse Source

add quick and dirty code to stabilize laser

master
parent
commit
37550eb2b3
  1. 92
      stabilize.py

92
stabilize.py

@ -0,0 +1,92 @@
import SoapySDR
import numpy as np
from scipy.signal import blackmanharris
import serial
fs = 5e6
base_freq = 1086e6
threshold = 0.4
target_freq = 1088.3e6
k = 200e-6
induction_min = 430e3
induction_max = 445e3
generator = serial.Serial("/dev/ttyUSB0", 57600, writeTimeout=0)
def set_induction_freq(freq):
command = ":s1f{:010d}\n".format(int(freq*1e2))
generator.write(command.encode())
generator.readline()
def set_induction(amount):
amount = max(min(amount, 0.5), -0.5)
freq = (induction_min + induction_max)/2 + amount*(induction_max - induction_min)
set_induction_freq(freq)
def parabolic(f, x):
"""Quadratic interpolation for estimating the true position of an
inter-sample maximum when nearby samples are known.
f is a vector and x is an index for that vector.
Returns (vx, vy), the coordinates of the vertex of a parabola that goes
through point x and its two neighbors.
Example:
Defining a vector f with a local maximum at index 3 (= 6), find local
maximum if points 2, 3, and 4 actually defined a parabola.
In [3]: f = [2, 3, 1, 6, 4, 2, 3, 1]
In [4]: parabolic(f, argmax(f))
Out[4]: (3.2142857142857144, 6.1607142857142856)
"""
xv = 1/2. * (f[x-1] - f[x+1]) / (f[x-1] - 2 * f[x] + f[x+1]) + x
yv = f[x] - 1/4. * (f[x-1] - f[x+1]) * (xv - x)
return (xv, yv)
def fmt_range(x, m):
pos = int(round(x*80/m))
return " "*pos + "*"
sdr = SoapySDR.Device()
samples = np.array([0]*4096, np.complex64)
sdr.setSampleRate(SoapySDR.SOAPY_SDR_RX, 0, fs)
sdr.setFrequency(SoapySDR.SOAPY_SDR_RX, 0, base_freq)
rxStream = sdr.setupStream(SoapySDR.SOAPY_SDR_RX, SoapySDR.SOAPY_SDR_CF32)
sdr.activateStream(rxStream)
decimation = 0
try:
while True:
sr = sdr.readStream(rxStream, [samples], len(samples))
if sr.ret != len(samples):
print("!")
continue
freqs = np.abs(np.fft.fft(samples*blackmanharris(len(samples)))[0:len(samples)//2])
for i in range(len(freqs)//100):
freqs[i] = 0
freqs[-i] = 0
# https://gist.github.com/endolith/255291
i = np.argmax(freqs)
true_i = parabolic(freqs, i)[0]
freq = 0.5 * fs * true_i / len(freqs)
amplitude = freqs[i]
if amplitude > threshold:
actual_freq = base_freq + freq
print("{:8.3f} {:6.2f} {}".format(actual_freq/1e6, amplitude, fmt_range(freq, fs/2)))
induction = (actual_freq - target_freq)*k
else:
print("<no signal>", amplitude)
induction = 0.0
decimation += 1
if decimation == 15:
set_induction(induction)
decimation = 0
finally:
sdr.deactivateStream(rxStream)
sdr.closeStream(rxStream)
Loading…
Cancel
Save