/
adc.py
executable file
·65 lines (50 loc) · 1.67 KB
/
adc.py
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#!/usr/bin/python3
# Tested on Raspberry Pi OS. Requirements: enable SPI, for example
# from raspi-config. The example is based on a SparkFun tutorial:
# https://learn.sparkfun.com/tutorials/python-programming-tutorial-getting-started-with-the-raspberry-pi/experiment-3-spi-and-analog-input
import signal
import sys
import time
import spidev
import RPi.GPIO as GPIO
spi_ch = 0
# Enable SPI
spi = spidev.SpiDev(0, spi_ch)
spi.max_speed_hz = 1200000
def close(signal, frame):
sys.exit(0)
signal.signal(signal.SIGINT, close)
def get_adc(channel):
# Make sure ADC channel is 0 or 1
if channel != 0:
channel = 1
# Construct SPI message
# First bit (Start): Logic high (1)
# Second bit (SGL/DIFF): 1 to select single mode
# Third bit (ODD/SIGN): Select channel (0 or 1)
# Fourth bit (MSFB): 0 for LSB first
# Next 12 bits: 0 (don't care)
msg = 0b11
msg = ((msg << 1) + channel) << 5
msg = [msg, 0b00000000]
reply = spi.xfer2(msg)
# Construct single integer out of the reply (2 bytes)
adc = 0
for n in reply:
adc = (adc << 8) + n
# Last bit (0) is not part of ADC value, shift to remove it
adc = adc >> 1
# Calculate voltage form ADC value
# considering the soil moisture sensor is working at 5V
voltage = (5 * adc) / 1024
return voltage
if __name__ == '__main__':
# Report the channel 0 and channel 1 voltages to the terminal
try:
while True:
adc_0 = get_adc(0)
adc_1 = get_adc(1)
print("ADC Channel 0:", round(adc_0, 2), "V ADC Channel 1:", round(adc_1, 2), "V")
time.sleep(0.2)
except KeyboardInterrupt:
GPIO.cleanup()