Test code for capacitive switch on raspberry pi.

capswitch.py

import wiringpi
import time

# 1M external pull-up resistor
# 1) set pin low and to output to discharge
# 2) make the pin an input without the internal pull-up on
# 3) read input and see how long it takes to go high

# ref: https://github.com/WiringPi/WiringPi-Python
# pins: https://projects.drogon.net/raspberry-pi/wiringpi/pins/
# functions: https://projects.drogon.net/raspberry-pi/wiringpi/functions/

def set_led(is_on):
    steps = 100
    for i in range(0,steps):
        v1 = int((i+0.0)/steps * 100)
        v2 = 100 - v1
        if is_on:
            wiringpi.softPwmWrite(r_pin, v1)
            wiringpi.softPwmWrite(b_pin, v2)
        else:
            wiringpi.softPwmWrite(r_pin, v2)
            wiringpi.softPwmWrite(b_pin, v1)
        time.sleep(0.005)
            
def toggle_led(led_on):
    led_on = 1 - led_on
    set_led(led_on)
    return led_on
    

io = wiringpi.GPIO(wiringpi.GPIO.WPI_MODE_PINS)
v_pin = 2
s_pin = 3
r_pin = 4
b_pin = 5
io.pinMode(s_pin, io.OUTPUT)
io.pinMode(v_pin, io.OUTPUT)
io.digitalWrite(v_pin, io.HIGH)

r_pwm = wiringpi.softPwmCreate(r_pin, 0, 100)
b_pwm = wiringpi.softPwmCreate(b_pin, 0, 100)

led_on = True
set_led(led_on)

while 1:
    repeats = 2
    total = 0.0
    for i in range(0,repeats):

        # 1) set pin low and to output to discharge
        io.pinMode(s_pin, io.OUTPUT)
        io.digitalWrite(s_pin, io.LOW)
    
        # 2) make the pin an input without the internal pull-up on
        io.pinMode(s_pin, io.INPUT)
        io.pullUpDnControl(s_pin, io.PUD_OFF)
        # 3) read input and see how long it takes to go high
        maxCycles = 1000
        cycles = 0

        while (cycles<maxCycles and io.digitalRead(s_pin)==0):
            cycles+=1;

        total += cycles

    mean = total / repeats
    #print mean
    #time.sleep(0.05)
    
    if (mean > 40):
        log_time()
        print mean
        led_on = toggle_led(led_on)