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)