How to run Raspberry Pi GPIO input buttons asynchronously?

Question

import RPi.GPIO as GPIO
import time
import os
import subprocess
GPIO.setmode(GPIO.BCM)

GPIO.setup(18, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(17, GPIO.IN, pull_up_down=GPIO.PUD_UP)
while True:
        input_state=GPIO.input(18)
        input_state1=GPIO.input(17)
        if input_state==False:
                print('Scan Button Pressed')
                subprocess.call(['./ocr.sh'])
        if input_state1==False:
                print('Read Button Pressed')
                subprocess.call(['aplay','temp1.wav'])

If input 17 is sensed temp.wav will play, while the audio file is playing input 18 cannot be checked. How to check for such a thing in between of a running process?

Answer 1

I am using a service called pigpiod and rinnung this service on my raspberry pi. I have python library installed for pigpiod service (daemon).
and my code to detect the button state is something like

!/usr/bin/env python
import pigpio
import time
import datetime

if __name__ == "__main__":
    def cbf(gpio, level):
        if(pi.read(gpio)!=0):
            i = datetime.datetime.now()
            date = i.strftime("%Y-%m-%d %H:%M:%S")
            print "gpio "+str(gpio)+"button gpio gave 1"

            print date
        if(pi.read(gpio)==0):
            i = datetime.datetime.now()
            date = i.strftime("%Y-%m-%d %H:%M:%S")
            print "gpio "+str(gpio)+"button gpio gave 0"

            print date
    pi = pigpio.pi()
    pi.set_mode(23, pigpio.INPUT)
    while True:
        cbf(23, pigpio.EITHER_EDGE)

Run the python script and press the button. You will get different value as 0 and 1.

So basically I am using PIGPIO and Python to detect button press as well as circuit close or open on a specific GPIO of the raspberry PI.

To start the pigpio daemon

sudo pigpiod

To stop the pigpio daemon

sudo killall pigpiod

github

git clone https://github.com/joan2937/pigpio

Python Library

sudo apt-get update
sudo apt-get install pigpio python-pigpio python3-pigpio

• Link for PIGPIO
• Download & Install PIGPIO and Run the PIGPIOD service

NOTE: I am NOT using RPi.GPIO or GPIO service available on Raspberry. All I have used pigpio for my temperature sensor, RFID card readers etc.