Python using MCP3008 sample frequency

Question

I am trying to make project of visible light communication. Currently I am using a classic LED as TX part and BPW21 photodiode with MCP3008 AD convertor as a RX part. Both of this part run on the RasPi4 withy python 3.7.3. However I have problem with receiving the bits using OOK modulation on RX part.

import busio
import digitalio
import board
import time
import adafruit_mcp3xxx.mcp3008 as MCP
from adafruit_mcp3xxx.analog_in import AnalogIn

spi = busio.SPI(clock=board.SCK, MISO=board.MISO, MOSI=board.MOSI)
cs = digitalio.DigitalInOut(board.D5)
mcp = MCP.MCP3008(spi, cs)
channel_0 = AnalogIn(mcp, MCP.P0)

def evaluateSensorValue():

    bits = ""

    sensor_value = channel_0.value
    channel_voltage = channel_0.voltage

    if channel_voltage < 3.0:
        bits = "1"
        print("1")
    else:
        bits = "0"
        print("0")

while True:
    evaluateSensorValue()
    time.sleep(0.05)

I am reading input from the Channel 0 of MCP3008. However in such a low frequency of 20Hz, I am not able to "catch" all the bits. BPW21 has fast response time to light in 1.5 us fall and rise time. I thouht that MCP3008 will be fast enough to catch all the bits in frequency of 10 kHz, not only lower than 20 Hz. How can I make it way much faster on RX side to be able to receive data in higher frequencies? Thank you for any kind of help!

Answer 1

This answer is solved. The problem was in the very high sampling frequency of the AD converter.