RPi.GPIO library limitation - add_event_detect cache

Question

How many callback events is cached in add_event_detect function? In my example below start_thread is executed just twice, but it is fired up five times (by the loop). To me it looks, that GPIO library is not able to hold more than 2 callback requests. or have i missed anything?

import time
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
start_thread_id = 1
_gpin = 10
i = 0
def start_thread(channel):
 global start_thread_id
 print("_***** F: start_thread called")
 for i in range(0, 5):
 print("doing job for thread #{}:".format(start_thread_id))
 time.sleep(0.3)
 start_thread_id += 1
 return
GPIO.setup(
 _gpin,
 GPIO.IN,
 pull_up_down=GPIO.PUD_UP
 )
GPIO.add_event_detect(
 _gpin, GPIO.RISING,
 callback=start_thread,
 bouncetime=5
 )
while True:
 if i <= 5:
 print("_gpin change #{}".format(i))
 GPIO.setup(_gpin, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
 time.sleep(.1)
 GPIO.setup(_gpin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
 else:
 time.sleep(40)
 break
 i += 1

Answer 1

I have no reason to doubt that your tests are correct for the RPi.GPIO Python module.

If you need to have more events queued you could use the pigpio Python module. It will queue up hundreds of events.

pigpio callbacks

• B.Ondrej: Thanks, I will give a try to pigpio
• B.Ondrej: Confirming the pigpio works as expected in terms of events caching