NanoVNAのテスト用コード。シリアル経由でデータを取ってきて、波形とスペクトラムをプロット。

plotdata.py

#!/usr/bin/env python
import serial
import numpy as np
import pylab as pl

dev = '/dev/cu.usbmodem401'
ser = serial.Serial(dev)

def fetch_data():
    ser.write("data 0\r")
    ser.readline() # discard empty line
    result = ''
    line = ''
    while True:
        c = ser.read()
        if c == chr(13):
            next # ignore CR
        line += c
        if c == chr(10):
            result += line
            line = ''
            next
        if line.endswith('ch>'):
            break
    ser.close()
    return result

def fetch_buffer():
    data = fetch_data()
    x = []
    for line in data.split('\n'):
        if line:
            x.extend([int(d, 16) for d in line.strip().split(' ')])
    return np.array(x, dtype=np.int16)

N = 256
fs = 48000

def plot_buffer():
    buf = fetch_buffer()
    samp = buf[1::2]
    ref = buf[0::2]

    pl.subplot(211)
    pl.grid()
    pl.plot(samp)
    pl.plot(ref)
    pl.subplot(212)
    pl.grid()
    pl.ylim((-50, 50))
    pl.psd(samp, N, window = pl.blackman(N), Fs=fs)
    pl.psd(ref, N, window = pl.blackman(N), Fs=fs)

plot_buffer()
pl.show()