RaspberryPi Stopwatch (TKinter) with Trigger - python-3.x

Question

i would like to build a stopwatch for my carrera track which i built a little bit bigger.
So I have bought a Raspberry Pi 3 with an additional 7 "touch screen and the individual modules for triggering.
Everything works fine individually.
Now I found a great stopwatch on the net which I also used. Works really great.
In another script, that I've written by myself, the triggering with the gpios works also fantastic.
Now I want to combine both and fail.
Does anyone have an idea or suggested solution where my mistake is?
Here is my code
#!/usr/bin/python
import tkinter as tk
import RPi.GPIO as GPIO
import time
GPIO_TRIGGER_PIN = 17
GPIO.setmode(GPIO.BCM)
GPIO.setup(GPIO_TRIGGER_PIN, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
GPIO.setwarnings(False)
def update_timeText():
if (state):
global timer
timer[2] += 1
if (timer[2] >= 100):
timer[2] = 0
timer[1] += 1
if (timer[1] >= 60):
timer[0] += 1
timer[1] = 0
timeString = pattern.format(timer[0], timer[1], timer[2])
timeText.configure(text=timeString)
root.after(10, update_timeText)
def start():
global state
state = True
print('Pressed Start')
def stop():
global state
state = False
print('Pressed Stop')
def reset():
global timer
timer = [0, 0, 0]
timeText.configure(text='00:00:00')
print('Pressed Reset')
while GPIO.input(GPIO_TRIGGER_PIN) == True:
if GPIO.input(GPIO_TRIGGER_PIN):
print('CAR DETECTED')
time.sleep(0.1)
state = False
# BULDING TKinter GUI
root = tk.Tk()
root.wm_title('Stopwatch')
timer = [0, 0, 0]
pattern = '{0:02d}:{1:02d}:{2:02d}'
timeText = tk.Label(root, text="00:00:00", font=("Helvetica", 150))
timeText.pack()
startButton = tk.Button(root, text='Start', command=start)
startButton.pack()
stopButton = tk.Button(root, text='Stop', command=stop)
stopButton.pack()
resetButton = tk.Button(root, text='Reset', command=reset)
resetButton.pack()
update_timeText()
root.mainloop()
Currently I get the trigger in the console as output "CAR DETECTED". However, I do not get the TKinter panel.
If I remove
while GPIO.input(GPIO_TRIGGER_PIN) == True:
if GPIO.input(GPIO_TRIGGER_PIN):
print('CAR DETECTED')
time.sleep(0.1)
then the display appears and works. Without triggering.
If I put it all down, I get also the panel but it also triggers nothing more.
Any ideas ?
Thanks for help

Answer 1

Not really my area of expertise, but since nobody else answered, I'll give it a shot.
I think you want to use GPIO.add_event_callback()* to add a callback that gets called when an event happens.
# Callback function
def on_trigger(channel_number):
# Just update the flag
global state
state = False
# Set the callback
GPIO.add_event_callback(GPIO_TRIGGER_PIN , callback=on_trigger)
Then, delete the while loop.
*According to the docs, you need the darksidesync library to use this function. Instead of the callback, you could also create a separate thread. Personally, I would prefer the callback.
from threading import Thread
def thread_function(arg):
global state
# Listen for state change
while GPIO.input(GPIO_TRIGGER_PIN) == True:
if GPIO.input(GPIO_TRIGGER_PIN):
# Update var
state = False
print('CAR DETECTED')
time.sleep(0.1)
thread = Thread(target = thread_function)
thread.start()
Hope this helps.