FFT spectrum demo for Maixduino

fft.py

#######################################
# FFT spectrum demo for Maixduino
# original:https://github.com/sipeed/MaixPy_scripts/blob/master/hardware/demo_fft_spectrum.py
# Maixduino sch:http://dl.sipeed.com/MAIX/HDK/Maixduino/Maixduino-4.30/Maixduino-4.30%28schematic%29.pdf
# mic data sheet:http://dl.sipeed.com/MAIX/HDK/Chip_DS/%E9%BA%A6%E5%85%8B_MSM261S4030H0%28%E4%BD%BF%E7%94%A8%E7%9A%84%29.pdf
#######################################

from Maix import GPIO, I2S, FFT
import image, lcd, math
from board import board_info
from fpioa_manager import fm

sample_rate = 38640
sample_points = 1024
fft_points = 512
hist_x_num = 100

lcd.init(freq=15000000)

# close WiFi
fm.register(8,  fm.fpioa.GPIO0)
wifi_en=GPIO(GPIO.GPIO0,GPIO.OUT)
wifi_en.value(0)

fm.register(20,fm.fpioa.I2S0_IN_D0)
fm.register(19,fm.fpioa.I2S0_WS)
fm.register(18,fm.fpioa.I2S0_SCLK)

rx = I2S(I2S.DEVICE_0)
rx.channel_config(rx.CHANNEL_0, rx.RECEIVER, align_mode = I2S.STANDARD_MODE)
rx.set_sample_rate(sample_rate)

img = image.Image()
if hist_x_num > 320:
    hist_x_num = 320
hist_width = int(320 / hist_x_num)#changeable
x_shift = 0

while True:
    audio = rx.record(sample_points)
    fft_res = FFT.run(audio.to_bytes(),fft_points)
    fft_amp = FFT.amplitude(fft_res)
    img = img.clear()
    x_shift = 0
    for i in range(hist_x_num):
        if fft_amp[i] > 240:
            hist_height = 240
        else:
            hist_height = fft_amp[i]
        img = img.draw_rectangle((x_shift,240-hist_height,hist_width,hist_height),[255,255,255],2,True)
        x_shift = x_shift + hist_width
    lcd.display(img)
    fft_amp.clear()