I'm new to Python.
I've a threaded callback code working fine on my raspi.
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
import time
from daemon import runner
GPIO.setup(23, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) # float switch goes down (closed to open) => low water level
GPIO.setup(24, GPIO.IN, pull_up_down=GPIO.PUD_UP) # float switch goes up (opened to close) => high water level
def callback_lowlevel(channel):
if GPIO.input(channel):
print "Low water level in the sump detected"
else:
print "Water level in the sump returned to normal"
def callback_highlevel(channel):
if GPIO.input(channel):
print "High water level in the sump detected"
else:
print "Water level in the sump returned to normal"
GPIO.add_event_detect(23, GPIO.BOTH, callback=callback_lowlevel, bouncetime=1000)
GPIO.add_event_detect(24, GPIO.BOTH, callback=callback_highlevel, bouncetime=1000)
If I start an infinite loop like this:
try:
print "Waiting for events"
while True:
time.sleep(1)
except KeyboardInterrupt:
GPIO.cleanup() # clean up GPIO on CTRL+C exit
GPIO.cleanup() # clean up GPIO on normal exit
It works.
But if I "daemonize" it with the daemon library, my threaded callbacks are just not working anymore.
class App(): # Daemon content, not doing much, sleeping mostly, to lower CPU footprint
def __init__(self):
self.stdin_path = '/dev/null'
self.stdout_path = '/dev/stdout'
self.stderr_path = '/dev/stdout'
self.pidfile_path = '/var/run/aquamonitor.pid'
self.pidfile_timeout = 5
def run(self):
Logger("Starting monitoring")
while True:
time.sleep(1) # Sleep most of time to be not too CPU intensive
app = App() # Init the App
daemon_runner = runner.DaemonRunner(app) # Run as a daemon
daemon_runner.do_action() # Just do it
What am I doing wrong? Does the fact that it's a daemon changes the way I'm supposed to write my threaded callbacks?
I had the same issue and I figured I was registering the callback to the wrong thread. So, long story short, be sure that GPIO.add_event_detect is called from within the run method of your App class, just before the loop.
Related
I have the following scenario. With a raspberry pi I have a main function which runs in a while loop and alternates tasks between calls to sleep. I would like a button press to interrupt the main loop and do another task for a certain amount of time before returning to the main loop. In reality I am displaying output on an LCD screen but I coded up this simpler example to illustrate the problem with my logic. I think things are getting crossed up because both functions seem to be active at the same time? I don't know the correct way to handle this scenario. Can someone suggest how to do this properly?
from time import sleep
import RPi.GPIO as GPIO
BUTTON_PIN = 2 # GPIO pin for mode button
def main():
print("mode1 part A")
sleep(4)
print("mode1 part B")
sleep(4)
def run_mode_two():
# I would like this function to full execute before retuning to main
print("mode2")
sleep(8)
# function to be called by interrupt
def button_released_callback(channel):
run_mode_two()
# intialize gpio for button
GPIO.setmode(GPIO.BCM)
GPIO.setup(
BUTTON_PIN,
GPIO.IN,
pull_up_down = GPIO.PUD_UP)
# interrupt to listen for button push
GPIO.add_event_detect(
BUTTON_PIN,
GPIO.RISING,
callback = button_released_callback,
bouncetime = 300)
while True:
main()
The following pseudo code for your reference. Only focus on the flow, please adapt it to your own needs.
mode = 1
def button_callback():
mode = 2
start_timer(5)
def timer_callback():
mode = 1
def loop():
if mode == 1:
# run code in mode 1
else:
# run code in mode 2
def main():
# init code here
# ...
while True:
loop()
Using openhab2 on machine A. Machine B is a RPi which controls a relay.
Using pigpio and gpiozero from machine a to control machine b gpio pins.
Using below script for testing. How can I rewrite this so that the on/off function in openhab will work? as of now it just loops between on and off.
help a noob please
#!/usr/bin/python
# https://gpiozero.readthedocs.io/en/stable/
# https://gpiozero.readthedocs.io/en/stable/api_output.html#outputdevice
import sys
import time
import gpiozero
relay = gpiozero.OutputDevice(18, active_high=False, initial_value=False)
def set_relay(status):
if status:
print("Setting relay: ON")
relay.on()
else:
print("Setting relay: OFF")
relay.off()
def toggle_relay():
print("toggling relay")
relay.toggle()
def main_loop():
while 1:
# then toggle the relay every second until the app closes
toggle_relay()
# wait a second
time.sleep(1)
if __name__ == "__main__":
try:
main_loop()
except KeyboardInterrupt:
# turn the relay off
set_relay(False)
print("\nExiting application\n")
# exit the application
sys.exit(0)
I am writing python code on raspberry pi 3. I am registering an event on input channel 21, to check moisture detection. I am getting this error Runtime error:Failed to add edge detection.
My code is:
import RPi.GPIO as GPIO
import sys,os
import time
import datetime
channel = 21
led_output = 18
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(channel, GPIO.IN)
GPIO.setup(led_output, GPIO.OUT)
def callback(channel):
filehandle = open("output.txt", "w") or die ("Could not write out")
if GPIO.input(channel) == 1:
print ("Water Detected!")
filehandle.write("1")
GPIO.output(led_output, GPIO.LOW)
else:
print ("Water Not Detected!")
filehandle.write("0")
GPIO.output(led_output, GPIO.HIGH)
filehandle.close()
GPIO.add_event_detect(channel, GPIO.BOTH, bouncetime=300)
GPIO.add_event_callback(channel, callback)
print(GPIO.input(channel))
while True:
time.sleep(5)
When I reboot the Raspberry and run your code it works perfect.
Only after killing the process or CTRL-C keyboard interrupting and running it again the problem/error occurs. I think this has to do with the fact that you exit the program without cleaning up properly...
I got it working in case you exit the running the program with CTRL-C with the code below in which I included a GPIO.cleanup()
However...this unfortunately it does not cover the situation in which you simply kill the running programm...In that case you still need to reboot.
So there is room for improvement.
Please re-insert your own file management commands again.
import RPi.GPIO as GPIO
import sys,os
import time
import datetime
channel = 21
led_output = 18
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(channel, GPIO.IN)
GPIO.setup(led_output, GPIO.OUT)
def callback(channel):
if GPIO.input(channel) == 1:
print ("Water Detected!")
GPIO.output(led_output, GPIO.LOW)
else:
print ("Water Not Detected!")
GPIO.output(led_output, GPIO.HIGH)
GPIO.add_event_detect(channel, GPIO.BOTH, bouncetime=300)
GPIO.add_event_callback(channel, callback)
print(GPIO.input(channel))
try:
while True:
#main loop here with some (dummy) code
eg_set_a_dummy_variable = 0
except KeyboardInterrupt:
# here you put any code you want to run before the program
# exits when you press CTRL+C
print ("Program interrupted by CTRL-C")
except:
# this catches ALL other exceptions including errors.
# You won't get any error messages for debugging
# so only use it once your code is working
print ("Other error or exception occurred!")
finally:
# this ensures a clean exit and prevents your
# error "Runtime error:Failed to add edge detection"
# in case you run your code for the second time after a break
GPIO.cleanup()
# credits to:
# https://raspi.tv/2013/rpi-gpio-basics-3-how-to-exit-gpio-programs-cleanly-avoid-warnings-and-protect-your-pi
It is not very clean solution, but you can call GPIO.cleanup() at the start of your script too for case when your process was killed before and GPIO.cleanup() was not called.
I build a keypad activated sensor with a Raspberry Pi and Python. Everything seems to go well but after a few minutes and several keypad entries, the Pi has a total crash and switches off immediately - no error messages pop up.
The script will continously wait for a keypad entry and if the code is correct, switch on a sensor, if it's not you have to try again. If the sensor is activated you have to put in the correct numbers to avoid an alarm being triggered after 30s)
Could anyone point me in the direction of what might be the problem? Here are the things I've tried so far without success
1) Exchange Pi to new Pi 2
2) Different OS, both NOOBS and Raspbian Wheezy
3) Different sensor (accelerometer vs IR sensor)
4) Disconnect monitor, keyboard and use SSH connection via Cygwin
5) Get log file until crash - log file was empty after reboot
python bad_script &> full_log.txt
6) Different log file command: causes instant crash and is also empty after reboot:
python script.py >> /logdir/script.py.log 2>&1
The question is: how am I able to crash Linux? If it's a memory problem, isn't there a prevention in linux to stop processed before they appear?
Here is the full script I am running:
import sys
from time import sleep
import threading
import signal
from matrix_keypad import RPi_GPIO1
import RPi.GPIO as GPIO
import smbus
import time
passcode = [1,2,3,4] # this is the correct code you have to enter
kp = RPi_GPIO1.keypad(columnCount = 3)
alarm_active = threading.Event() # shared variable used to control the sensor monitoring thread
alarm_active.clear() # Clear the alarm initially
monitor_thread = None # Global variable used to store the monitoring thread
#Set up all the pins correctio
GPIO.setmode(GPIO.BCM)
PINIR=7
GPIO.setup(7, GPIO.IN) # infrad-sensor
#Now activate the kaypad and listen for keypad inputs
def digit():
r = None
while r == None:
r = kp.getKey()
return r
def get_keycode():
# Function to loop around reading 4 keypresses in a row
# Compare against chosen code
# If match, switch the alarm state
entered = []
while len(entered) < 4:
key = digit()
sleep(0.5)
print key
entered.append( key )
if entered == passcode:
entered = []
print "Code correct"
switch_alarm_state()
else:
# Just clear the keypad buffer if the wrong code went in
# Could say "BAD CODE!" here, or even force immediate alarm perhaps
print "Wrong Code - Try again"
GPIO.output(27, True) # let red LED blink as indicator that code was wrong
time.sleep(1)
GPIO.output(27, False)
entered = []
def switch_alarm_state():
# Function to control the state of the alarm
# If the alarm should be on, run a thread monitoring the sensor
# If the alarm should be off, make sure the thread is stopped
global monitor_thread
if alarm_active.is_set():
# If the alarm is currently set, stop it
print "Alarm was abolished"
GPIO.output(17, False) #switch green LED off
alarm_active.clear() # Signals to the monitor thread that we wish to shut it down
monitor_thread.join() # Wait until the monitor thread has stopped
else:
# Alarm is not currently set, so start the sensor monitor thread going
print "Alarm was activated"
GPIO.output(17, True)
monitor_thread = threading.Thread( target=sensor_monitor )
alarm_active.set()
monitor_thread.start()
def sensor_monitor():
# Function to be run in a separate thread, monitoring the sensor
alarm_timer = None # Variable to hold a timer object that will fire the alarm
while alarm_active.is_set():
#print xrota
if GPIO.input(PINIR):
print "Alarm has been triggered"
if alarm_timer is None:
alarm_timer = threading.Timer( 30.0, fire_alarm )
alarm_timer.start()
sleep(0.5)
# The alarm must have been deactivated to get here
# Stop any outstanding alarms and shutdown
if alarm_timer is not None:
alarm_timer.cancel()
return
def fire_alarm():
# Here you implement the actions to be carried out by an alarm
print "Alarm is send to server"
msg = "Alarm"
publish.single("alarm/demo",msg, hostname="52.17.194.125")
def shutdown_handler( signum, frame ):
# Shut down the child thread nicely
alarm_active.clear()
monitor_thread.join()
if __name__ == '__main__': # This is the Python way to check you are being directly run, and not just imported by another script
signal.signal( signal.SIGINT, shutdown_handler ) # If you stop the script with ctrl+C, make sure it shuts down properly
signal.signal( signal.SIGTERM, shutdown_handler )
try:
while True:
get_keycode()
except KeyboardInterrupt:
GPIO.cleanup()
print "Quit program"
I got a piece of code in Python from here:
http://www.raspberry-pi-geek.com/Archive/2013/01/Adding-an-On-Off-switch-to-your-Raspberry-Pi
And I wanted to improve on it.
Since this is the first time I work with Python, I got stuck on understanding what actually happens.
Here is the code:
# Import the modules to send commands to the system and access GPIO pins
from subprocess import call
import RPi.GPIO as gpio
from time import sleep
gpio.setmode(gpio.BCM) # Set pin numbering to board numbering
gpio.setup(22, gpio.IN) # Set up pin 22 as an input
rebootBool = 0
# Define a function to keep script running
def main(pin):
while True:
#gpio.remove_event_detect(pin)
gpio.add_event_detect(22, gpio.RISING, callback=confirmation, bouncetime=200) # Set up an interrupt to look for button presses
sleep(5000000)
def confirmation(pin):
gpio.remove_event_detect(pin)
gpio.add_event_detect(22, gpio.RISING, callback=shutdown, bouncetime=200)
sleep(3) # if button has been pressed again within 3 seconds, shut down will happen
main(22)
def reboot(pin):
rebootBool = 1
call('reboot', shell=False)
exit(0)
# Define a function to run when an interrupt is called
def shutdown(pin):
gpio.remove_event_detect(pin)
gpio.add_event_detect(22, gpio.RISING, callback=reboot, bouncetime=200)
sleep(3) # if the button has been pressed for a third time, within 3 seconds, Pi will reboot
if rebootBool == 0: # Just to make sure a halt is not called after the 3 seconds have passed, if reboot is called
call('halt', shell=False)
exit(0)
main(22) # Run the loop function to keep script running
What I want to do is this:
If button is pressed once, a confirmation function is executed, in which it resets the button to call the shutdown function, if it's pressed within 3 seconds.
Else, resume with the main loop
In the shutdown function, if it's pressed again (within 3 seconds), it resets to call the reboot function.
Else go on, and shut down
What happens is this:
If I press the button twice or three times, it tells me that gpio.add_event_detect is already defined, when it tries to define it in main().
So it doesn't change it, and if I press it one more time, it calls the shutdown function.
What I don't understand is:
Why does it want to define the gpio event in main, when the actual function is either reboot or shutdown (and it should call either reboot or shutdown)?
Because a callback function is running in a separate thread. This means, for example, when you call any callback function in the main loop it still works(main loop), and thus it happens when you call a function gpio.add_event_detect from a callback function(thread #1) and from the main loop(thread #2) at the same time. It's typical race condition.
You can check it by running this code:
#!/usr/bin/python
# Import the modules to send commands to the system and access GPIO pins
from subprocess import call
import RPi.GPIO as gpio
from time import sleep
gpio.setmode(gpio.BCM) # Set pin numbering to board numbering
gpio.setup(22, gpio.IN, pull_up_down=gpio.PUD_DOWN) # Set up pin 22 as an input
rebootBool = 0
# Define a function to keep script running
def main(pin):
while True:
print "main loop"
gpio.remove_event_detect(22)
gpio.add_event_detect(22, gpio.RISING, callback=confirmation, bouncetime=200) # Set up an interrupt to look for button presses
sleep(1)
#raw_input()
def confirmation(pin):
print "confirmation1"
sleep(5)
print "confirmation2"
gpio.remove_event_detect(22)
gpio.add_event_detect(22, gpio.RISING, callback=shutdown, bouncetime=200)
sleep(5) # if button has been pressed again within 3 seconds, shut down will happen
gpio.remove_event_detect(22)
main(22)
def reboot(pin):
rebootBool = 1
print "reboot"
#call('reboot', shell=False)
exit(0)
# Define a function to run when an interrupt is called
def shutdown(pin):
print "shutdown"
gpio.remove_event_detect(pin)
gpio.add_event_detect(22, gpio.RISING, callback=reboot, bouncetime=200)
sleep(3) # if the button has been pressed for a third time, within 3 seconds, Pi will reboot
if rebootBool == 0: # Just to make sure a halt is not called after the 3 seconds have passed, if reboot is called
#call('halt', shell=False)
print "halt"
exit(0)
main(22) # Run the loop function to keep script running
So, after Anton Glukhov explained me what to look out for, I found out how to solve every issue, and now it's working flawlessly.
This is the link that better explains what I did:
http://sourceforge.net/p/raspberry-gpio-python/wiki/Inputs/
Unfortunately, I wasn't able to do it any other way than use a while loop in the main function.
But since there is nothing critical going on, a sleep of 1 second has been added to each loop, ensuring minimal CPU usage.
I am sharing the final code here, in hopes that it might help others:
# Import the modules to send commands to the system and access GPIO pins
from subprocess import call
import RPi.GPIO as gpio
from time import sleep
from os import system
gpio.setmode(gpio.BCM) # Set pin numbering to BCM numbering
gpio.setup(22, gpio.IN) # Set up pin 22 as an input
def confirmation(pin):
#print "Confirmation Function on pin %d" % pin
system('echo Press again to confirm Shut down menu! | wall -n') # let all logged in users know
gpio.remove_event_detect(pin)
gpio.add_event_detect(pin, gpio.RISING, bouncetime=200)
sleep(2) # if button has been pressed again within 2 seconds, shut down function is called
if gpio.event_detected(pin):
shutdown(pin)
else:
#print "canceled"
system('echo Shut down canceled! | wall -n') # let all logged in users know
main()
def resetPin(pin):
#print "Pin %d has been reset" % pin
gpio.remove_event_detect(pin)
gpio.add_event_detect(pin, gpio.RISING, bouncetime=200)
def reboot(pin):
#print "Reboot Function on pin %d" % pin
call('reboot', shell=False)
exit(0)
# Define a function to run when an interrupt is called
def shutdown(pin):
#print "ShutDown function on pin %d" % pin
system('echo Press again if you want to reboot instead of shut down! | wall -n') # let all logged in users know
gpio.remove_event_detect(pin)
gpio.add_event_detect(pin, gpio.RISING, bouncetime=200)
sleep(2) # if the button has been pressed for a third time, within 2 seconds, Pi will reboot
if gpio.event_detected(pin):
reboot(pin)
else:
call('halt', shell=False)
exit(0)
# Define a function to keep script running
def main():
#print "Main Function"
resetPin(22)
while True:
sleep(1)
if gpio.event_detected(22):
confirmation(22)
main() # Run the main function to keep script running