noptica2-sdr/noptica.py

import serial
import queue
import threading

import SoapySDR
import numpy as np
from scipy.signal import blackmanharris


class BufferedSDR:
    def __init__(self, sdr, channels, bufsize, nbufs):
        self.sdr = sdr
        self.channels = channels
        self.bufsize = bufsize

        self.stream = None
        self.terminate = False
        self.thread = None
        self.queue = queue.Queue(nbufs)
        self.available_buffers = queue.Queue(nbufs)
        for _ in range(nbufs):
            self.available_buffers.put([np.array([0]*bufsize, np.complex64) for _ in self.channels])

    def start(self):
        self.stream = self.sdr.setupStream(SoapySDR.SOAPY_SDR_RX, SoapySDR.SOAPY_SDR_CF32, self.channels)
        try:
            self.thread = threading.Thread(target=self.thread_target)
            self.thread.start()
        except:
            self.sdr.closeStream(self.stream)
            raise

    def stop(self):
        self.terminate = True
        self.thread.join()
        self.sdr.closeStream(self.stream)

    def get(self):
        return self.queue.get()

    def dispose(self, buffers):
        self.available_buffers.put(buffers)

    def thread_target(self):
        self.sdr.activateStream(self.stream)
        try:
            while not self.terminate:
                buffers = self.available_buffers.get()
                sr = self.sdr.readStream(self.stream, buffers, self.bufsize)
                if sr.ret != self.bufsize:
                    print("SDR sampling error")
                    return
                self.queue.put(buffers)
        finally:
            self.sdr.deactivateStream(self.stream)


class DummyInductionHeater:
    def __init__(self, port, induction_min, induction_max):
        pass

    def start(self):
        pass

    def set(self, amount):
        print("induction", amount)

    def stop(self):
        pass


class InductionHeater:
    """Interface to the MHS5200A function generator driving the LC tank"""
    def __init__(self, port, induction_min, induction_max):
        self.port = port
        self.induction_min = induction_min
        self.induction_max = induction_max
        self.queue = queue.Queue(1)

    def start(self):
        self.serial = serial.Serial(self.port, 57600)
        self.thread = threading.Thread(target=self.thread_target)
        self.thread.start()

    def thread_target(self):
        while True:
            amount = self.queue.get()
            if amount is None:
                break

            assert -0.5 <= amount <= 0.5
            freq = ((self.induction_min + self.induction_max)/2
                    + amount*(self.induction_max - self.induction_min))

            command = ":s1f{:010d}\n".format(int(freq*1e2))
            self.serial.write(command.encode())
            self.serial.readline()

    def set(self, amount):
        self.queue.put(amount, block=False)

    def stop(self):
        self.queue.put(0.0, block=True)
        self.queue.put(None, block=True)
        self.thread.join()
        self.serial.close()


class Stabilizer:
    def __init__(self, freq_sample, block_size, freq_target, cb):
        self.freqs = np.fft.fftfreq(block_size, d=1/freq_sample)
        self.freq_target = freq_target
        self.cb = cb

        self.lock_counter = 0
        self.unlock_counter = 0
        self.wiggle = 0.0

        self.amp_threshold = 80.0
        self.k = 30.0e-6
        self.tolerance = 10e3
        self.lock_counter_threshold = 60
        self.unlock_counter_threshold = 500
        self.wiggle_amplitude = 0.15

    def input(self, samples):
        spectrum = np.abs(np.fft.fft(samples*blackmanharris(len(samples))))
        i = np.argmax(spectrum)
        amplitude = spectrum[i]

        success = False
        if amplitude > self.amp_threshold:
            freq = self.freqs[i]
            delta = freq - self.freq_target
            tuning = delta*self.k
            if abs(delta) < self.tolerance:
                success = True
        else:
            freq = None
            tuning = 0.0
        max_tuning_abs = 0.5 - self.wiggle_amplitude - 1e-9
        tuning = max(min(tuning, max_tuning_abs), -max_tuning_abs)

        if success:
            self.lock_counter += 1
        else:
            self.lock_counter = 0

        if self.locked():
            self.unlock_counter = 0
        else:
            self.unlock_counter += 1
        if not success and (self.unlock_counter > self.unlock_counter_threshold):
            print("wiggle")
            self.wiggle = self.wiggle_amplitude*np.random.uniform(-1.0, 1.0)
            self.unlock_counter = 0

        self.cb(spectrum, freq, self.locked(), tuning + self.wiggle)

    def locked(self):
        return self.lock_counter > self.lock_counter_threshold


def continuous_unwrap(last_phase, last_phase_unwrapped, p):
    # note: np.unwrap always preserves first element of array
    p = np.unwrap(p)
    glue = np.array([last_phase_unwrapped, last_phase_unwrapped + (p[0] - last_phase)])
    new_p0 = np.unwrap(glue)[1]
    return new_p0 + p - p[0]


class PositionTracker:
    def __init__(self):
        self.reset()

    def reset(self):
        self.last_phase = 0.0
        self.last_position = 0.0

    def input(self, ref, meas):
        demod = np.conjugate(ref)*meas
        phase = np.angle(demod)
        position = continuous_unwrap(self.last_phase, self.last_position, phase)/(2.0*np.pi)
        self.last_phase = phase[-1]
        self.last_position = position[-1]
        return position