Raspberry PI with GPIO Input buttons - python-3.x

Question

I have a PI running with 4 GPIO input ports.
The target is, if one the 4 buttons will be pressed, a mp3 file should be played, i.e. button1 = file1.mp3, button2 = file2.mp3 and so on.
It seems to be no so complicate, but 'the devil is in the detail' :-)
This is my code for 2 buttons at moment :
#!/usr/bin/env python
#coding: utf8
import time
from time import sleep
import os
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(24, GPIO.IN, pull_up_down = GPIO.PUD_DOWN)
GPIO.setup(23, GPIO.IN, pull_up_down = GPIO.PUD_DOWN)
def my_callback_1(channel):
print("Button 23 Pressed")
os.system('omxplayer -o both /root/1.mp3')
sleep(10)
def my_callback_2(channel):
print("Button 24 Pressed")
os.system('omxplayer -o both /root/2.mp3')
sleep(10)
GPIO.add_event_detect(23, GPIO.RISING, callback=my_callback_1, bouncetime=200)
GPIO.add_event_detect(24, GPIO.RISING, callback=my_callback_2, bouncetime=200)
try:
while 1:
time.sleep(0.5)
except KeyboardInterrupt:
# exits when you press CTRL+C
print(" Bye Bye")
except:
print("Other error or exception occurred!")
finally:
GPIO.cleanup() # this ensures a clean exit
The sleep time is set for the longer of the mp3 file.
Its working, but not like I expected.
The problem is, when a buttons will be pushed while a file is already playing, the PI keeps the button push in a buffer and play the file after the current file in a loop.
Imagine, somebody will push 5 times the same button, 5 times the same mp3 file will be played in a loop.
So I searching for a solution like this:
While a file is playing, all Input buttons should be "disabled" for this time. When the mp3 file paying is finished, the buttons should be "re-enabled" and another button can be pushed.
How can I this ? Thanks for your help.

Answer 1

I don't see a simple way to do this without adding threads. Note that you are implicitly already using threads behind the scenes with add_event_detect(), which runs the callbacks in separate threads. If add_event_detect doesn't support suppressing the button presses (which I don't think it does), then you can thread it in one of two ways - using python threads or processes, or a simpler way by using bash.
To use background processes in bash, remove your add_event_detect calls, and then in your while loop, you'd do something like (untested):
started_23 = 0
while True:
if GPIO.input(23) and time.time() - started_23 > 10:
started_23 = time.time()
print("Button 23 Pressed")
os.system('omxplayer -o both /root/1.mp3 &')
time.sleep(0.200)
Note the ampersand added to the system() call - that will run the omxplayer in the background. And the started_23 variable keeps track of when the sound was started in order to prevent replaying it for another 10 seconds. You may way to increase that to include the length of the file time. You can similarly add in code for GPIO 24 in the same loop.

Answer 2

Thanks for help, Brian. You brought me in the right direction !
I got it. Its working now as I described above.
Here my code :
try:
vtc1 = 8 # Time Audiofile 1
vtc2 = 11 # Time Audiofile 2
vtc3 = 0 # Time Audiofile 3
vtc4 = 0 # Time Audiofile 4
vtc = 0 # Current AudioFileTime
started_t = 0 # Started Time
while True:
if GPIO.input(23) and time.time() - started_t > vtc:
vtc = vtc1
started_t = time.time()
print("Button 23 Pressed")
os.system('omxplayer -o both /root/1.mp3 &')
time.sleep(0.200)
if GPIO.input(24) and time.time() - started_t > vtc:
vtc = vtc2
started_t = time.time()
print("Button 24 Pressed")
os.system('omxplayer -o both /root/2.mp3 &')
time.sleep(0.200)
The problem was, that the seconded file was started before the first was finished. Because the code did not know the longer of currently played file. So I put the time of the audiofile in the "vtc" value when this file were executed.
If you push another button, it calculate the time playing with the current file time "vtc". That's it.
Thanks again.