Script for testing an IR sensor with the PCF8291 A/D converter on the Raspberry Pi

pcf8591test.py

#!/usr/bin/env python3
import smbus as smbus
import RPi.GPIO as GPIO
import time

DEV_ADDR = 0x48
FR_LED_PIN = 15

def LED_on():
    GPIO.output(15, 1) # LED on

def LED_off():
    GPIO.output(15, 0)

def read_sensor(sensor_no):
    aout = 0
    bus.write_byte(DEV_ADDR, 0x40 | ((sensor_no) & 0x03))
    bus.read_byte(DEV_ADDR)
    return bus.read_byte(DEV_ADDR)  # percentage of 3.3 V


GPIO.cleanup()
GPIO.setmode(GPIO.BOARD)
GPIO.setup(15, GPIO.OUT)

bus = smbus.SMBus(1)

channel = 0
ctr = 0

print("Polling on channel " + str(channel))
while True:
    try:
        print("=== reading " + str(ctr) + " ===")
        LED_off()
        baseline = read_sensor(channel)
        LED_on()
        value = read_sensor(channel)
        LED_off()

        over_baseline = value - baseline
        collision_perc = over_baseline / (255 - baseline)
        print("baseline: " + str(baseline) + " value: " + str(value))
        print("collision likeliness: {0:.2f} %".format(collision_perc * 100))

        dist = "["
        # around 30% are from environmental scattering of the IR light
        if collision_perc > 0.3:
            if collision_perc > 0.4:
                # > 50 % is already pretty close
                if collision_perc > 0.5:
                    dist = "[=]"
                else:
                    dist = "[==]"
            else:
                dist = "[===]"
        print("rating: distance is ", dist)
        time.sleep(0.5)
        ctr += 1
    except KeyboardInterrupt:
        LED_off()
        GPIO.cleanup()