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Python Threading for Camera

I am trying to put the camera footage into a different thread as the cv2.wait() does not work correctly anymore for access keys even when using an '& and hexadecimal'.
Does anyone know what I have done wrong with the daemon thread I have created for displaying camera footage in the main as when placed in the main while loop it fails while loop?
How do I use a thread to continuously display camera footage in my while loop in the main program?
quote My thread for the ViewCamera function isn't working right - can anyone help?
from djitellopy import Tello
# Access the telopy libray.
import cv2, math, time
from time import sleep, perf_counter
from threading import Thread
stop = True
def ViewCamera():
global stop
while stop == True:
try:
#camera window
img = frame_read.frame
cv2.imshow("drone", img)
print ('thread test')
except Exception as e:
print ("Cerror is : ,", e)
drone = Tello()
'''
create an instance of the Tellopy libray
drone.connect() #connect to drone using wifi
drone.streamon()
#make use of a data stream to drone to pass on keyboard commands
#frame_read = drone.get_frame_read() #read cammera data using frame per frame rate
'''
key = 0
# drone.takeoff()
if __name__ == "__main__":
print ('main program')
# Create a camera thread - runs in background.
t1 = Thread(target=ViewCamera, args=())
t1.daemon = True
print('starting thread')
t1.start()
while True:
key = ord(input('please enter letter'))
if key == ord('j'):
drone.land()
print('stopping thread')
stop = False
break
elif key == ord('w'): # Forward
drone.move_forward(30)
print('moving forwards')
elif key == ord('s'): # Move backwards
drone.move_back(30)
elif key == ord('a'): # Move left
drone.move_left(30)
elif key == ord('d'): # Move right
drone.move_right(30)
elif key == ord('e'): # Rotate right
drone.rotate_clockwise(30)
elif key == ord('q'): # Rotate left
drone.rotate_counter_clockwise(30)
elif key == ord('r'): # Move up
drone.move_up(30)
elif key == ord('f'): # Move down
drone.move_down(30)
print('stopping thread')
t1.join()
drone.land()
The threading daemon isn't seeming to work it should be running in background and continually allowing the camera images in a window to be viewed - any ideas why it is not?

Thread synchronization between a slow and a fast processing thread in Python

I'm working on automation of a vision based machine driven by stepper motor. Structure of my program is as followed.
import ImageProcessing
import Mechanices
import cv2
def rotate_motor(steps,direction):
global g_motor_ploc
DIR = 20 # Direction GPIO Pin
STEP = 21 # Step GPIO Pin
delay = .00055
GPIO.setmode(GPIO.BCM)
GPIO.setup(DIR, GPIO.OUT)
GPIO.setup(STEP, GPIO.OUT)
GPIO.output(DIR, direction)
for x in range(steps):
GPIO.output(STEP, GPIO.HIGH)
sleep(delay)
GPIO.output(STEP, GPIO.LOW)
sleep(delay)
GPIO.cleanup()
def findImage():
####################################
< Very Fast Image Processing Code >
####################################
return position_of_object
def calculate_steps(position):
####################################
< Very Fast Steps and Direction Calculation Code >
####################################
return steps_required,direction_of_rotation
def main():
while True:
position=findImage()
steps, direction = calculate_steps
rotate_motor(steps,directions) # Very Slow Process
if __name__ == "__main__":
main()
Despite very fast processing of images, whole program has to wait for rotate_motor to complete before processing next frame. In mean time if object moves backward it fails to see the change unless previously calculated position is achieved.
I'm looking forward to run rotate_motor in a separate thread and update the number_of_steps and direction required for motion. So that even if previously calculated position is not achieved, it should know how many more steps are required or change of direction is required.
So I modified the program as followed:
import multiprocessing as mp
import cv2
(r, g_w) = mp.Pipe(True)
g_motor_ploc = 0
def rotate_motor(steps,direction):
global g_motor_ploc
DIR = 20 # Direction GPIO Pin
STEP = 21 # Step GPIO Pin
delay = .00055
GPIO.setmode(GPIO.BCM)
GPIO.setup(DIR, GPIO.OUT)
GPIO.setup(STEP, GPIO.OUT)
GPIO.output(DIR, direction)
for x in range(steps):
GPIO.output(STEP, GPIO.HIGH)
sleep(delay)
GPIO.output(STEP, GPIO.LOW)
sleep(delay)
if direction==1:
g_motor_ploc -= 1
else:
g_motor_ploc += 1
GPIO.cleanup()
def findImage():
####################################
< Very Fast Image Processing Code >
####################################
return position_of_object
def calculate_steps(position):
####################################
< Very Fast Steps and Direction Calculation Code >
####################################
return steps_required,direction_of_rotation ## (Clockwise, Counter Clockwise)
def linear_motion(r):
global g_motor_ploc
while True:
loc = r.recv()
steps = loc - g_motor_ploc
if steps < 0:
direction = 1
else:
direction = 0
rotate_motor(abs(steps),direction)
def main():
while True:
position=findImage()
steps = calculate_steps
g_w.send(steps)
if __name__ == "__main__":
motor_proc = mp.Process(target=linear_motion, args=(r,))
motor_proc.daemon = True
motor_proc.start()
main()
Using the mp.Pipe() it interrupts the linear_motion() as soon as new position is send to the pipe. However this process if so fast that linear_motion never reach to the rotate_motor part.
Any suggestions, I'm confused.

Python - Detect input within a terminal screensaver

I'm writing a code that basically runs without a loop for the sake of mobility and functionality. Let's say that when I run the program I use the -i option to continue using the python interpreter as it loads every function written. The thing is that I'm using a screensaver like function after the program print some basic information to make it look not so boring.
My question is: How can I maintain the screen saver running without blocking the interpreter prompt. I already wrote how to handle keyboard input to stop it using curses "getch()". I tried using threading but with no avail as it doesn't detect any keyboard input so it keeps running.
Is there any way I can get around this? How can I detect any input without blocking therefore retaining the interpreter prompt?
Right know it detects an input and raise a KeyboardException captured to make the screensaver stop.
Thanks in advance
I'm using this code with some added modifications:
Matrix-Curses
What I have so far:
Completed Code
This are the modifications done to the code:
def clear(int=None):
""" Clear Terminal Screen """
from subprocess import call
call('clear')
if int == 0:
exit()
def Matrix():
steps = 0
global scr
curses.curs_set(0)
curses.noecho()
if USE_COLORS:
curses.start_color()
curses.use_default_colors()
curses.init_pair(COLOR_CHAR_NORMAL, curses.COLOR_GREEN, curses.COLOR_BLACK)
curses.init_pair(COLOR_CHAR_HIGHLIGHT, curses.COLOR_WHITE, curses.COLOR_GREEN)
curses.init_pair(COLOR_WINDOW, curses.COLOR_GREEN, curses.COLOR_GREEN)
height, width = scr.getmaxyx()
window_animation = None
lines = []
for i in range(DROPPING_CHARS):
l = FallingChar(width, MIN_SPEED, MAX_SPEED)
l.y = randint(0, height-2)
lines.append(l)
scr.refresh()
while True:
height, width = scr.getmaxyx()
for line in lines:
line.tick(scr, steps)
for i in range(RANDOM_CLEANUP):
x = randint(0, width-1)
y = randint(0, height-1)
scr.addstr(y, x, ' ')
if randint(0, WINDOW_CHANCE) == 1:
if window_animation is None:
#start window animation
line = random.choice(lines)
window_animation = WindowAnimation(line.x, line.y)
if not window_animation is None:
still_active = window_animation.tick(scr, steps)
if not still_active:
window_animation = None
scr.refresh()
time.sleep(SLEEP_MILLIS)
if SCREENSAVER_MODE:
key_pressed = scr.getch() != -1
if key_pressed:
raise KeyboardInterrupt
steps += 1
def ScreenSaver():
from time import sleep
from datetime import datetime as dt
global scr
TimeLimit = 10
StartTime = dt.now()
while True:
try:
sleep(1)
StopTime = (dt.now() - StartTime)
LastTime = StopTime.days*86400000 + StopTime.seconds*1000 + StopTime.microseconds/1000
if LastTime >= TimeLimit:
GetLocaleStatus = locale.getlocale()
locale.setlocale(locale.LC_ALL, '')
scr = curses.initscr()
scr.nodelay(1)
key_being_pressed = scr.getch() != -1
if not key_being_pressed:
try:
Matrix()
except KeyboardInterrupt:
TimeLimit = 30000
StartTime = dt.now()
raise KeyboardInterrupt
except KeyboardInterrupt:
curses.endwin()
curses.curs_set(1)
curses.reset_shell_mode()
curses.echo()
clear()
# return
main()

Raspberry Pi Python pause a loop sequence, when button pushed

I have a raspberry PI 2. With a relay board, what i use to for a switch sequence (like a traffic light).
I use a tool, called "webiopi" what create buttons on a website. When the button is clicked the function of the python script below is started.
What i want is to break out of the loop (or pause it) when another button is clicked. However, as long this loop is running, the tool don't look at the webpage
A kind of similar question is asked here Exiting a continuous loop in python via webiopi but this is for a single event and the solution doesn't work in my case.
Question is. How can I make this script look at a button what is clicked (can be a gpio switch as well) while the loop is running
GPIO_nek=11
GPIO_schouder=12
GPIO_rug1=8
GPIO_ONOFF=18
interval1 = 2
interval2 = 4
for x in range(0, 20):
GPIO.digitalWrite(GPIO_nek, GPIO.LOW)
time.sleep(interval1)
GPIO.digitalWrite(GPIO_schouder, GPIO.LOW)
time.sleep(interval1)
GPIO.digitalWrite(GPIO_nek, GPIO.HIGH)
time.sleep(interval1)
GPIO.digitalWrite(GPIO_rug1, GPIO.LOW)
time.sleep(interval2)
GPIO.digitalWrite(GPIO_schouder, GPIO.HIGH)
if (GPIO.digitalRead(GPIO_ONOFF) == GPIO.LOW):
GPIO.digitalWrite(GPIO_ONOFF, GPIO.HIGH)
break

When monitoring a real time event such as sensors or your button your best solution will be setting up a separate thread or process that contains nothing but an infinite loop that watches the resource and sets a flag when something interesting happens.
The example below sets up a process that automatically takes a picture on the RPI aprox. every minute.
#!/usr/bin/python
#Threading Prototype - Running a background thread that will take
# pictures at the appropriate time
#------------------------------------------------------------------
from multiprocessing import Queue
from multiprocessing import Process
from time import sleep
from datetime import datetime
from datetime import timedelta
from subprocess import call
#Doing the work ---------------------------------------------------
#Global Variables ---
messages = Queue()
start_time = datetime.now()
#Returns number of Milliseconds since start of program
def milliSinceStart():
global start_time
dt = datetime.now() - start_time
ms = (dt.days * 24 * 60 * 60 + dt.seconds) * 1000 + dt.microseconds / 1000.0
return ms
#Process Methods --------------------------------------------------
def processMessages():
print "Message Processor Launched"
while True:
print messages.get() #should halt until message in queue
sleep(0.1) #sleep for a tick just to avoid a run away process
def processPicutres():
print "Picture Taker Launched"
pictureCycleStart = milliSinceStart()
index = 0
while True:
if milliSinceStart() - pictureCycleStart > 10000: #once a minute
a = "blip" + str(index) + ".jpg"
b = "raspistill -n -t 100 -o " + a
messages.put("Click")
call ([b], shell=True)
messages.put("picture taken - " + b)
index = index + 1
pictureCycleStart = milliSinceStart()
sleep(0.1) #wait a tick -- don't hog processor time
def main():
print "MultiProcessing Prototype"
print "Launching message process"
Process(target=processMessages).start()
print "Back from launch"
print "Launching picture taking process"
Process(target=processPicutres).start()
print "Back from launch"
cycleStart = milliSinceStart()
index = 0
while True:
if milliSinceStart() - cycleStart > 1000:
messages.put("Tick " + str(index))
cycleStart = milliSinceStart()
index = index + 1
if __name__ == "__main__":
main()
The main method launches the Messaging and Picture processes and then sets up its own little infinite loop that does nothing more that display the message "Tick" every second. The picture process sets up a separate infinite loop, watching the clock and taking a picture periodically. The Message process monitors the picture process (again, an infinite loop) and when it detects that a picture has been taken, it outputs the fact to the screen.
The important part of this for your purpose is the message queue. The process queue is what is allowing the Picture and Message processes to communicate.
And because the task take place in different processes, it matters not if one process pauses as the others are always active. If you set up a button monitor process you can be checking message queue for this fact and halting your main program when the button is pressed. This pause in the main program would not effect the button process which could then pick up on the fact that the button is pressed again.

If the button is the GPIO switch as you mentioned at the end of the question, instead of the webpage button, then you can make use of an inbuilt GPIO interrupt function that saves your computer the resouces of constant polling:
import RPi.GPIO as GPIO
from threading import Event # We'll use it like time.sleep, but we can interrupt it.
GPIO_nek=11
GPIO_schouder=12
GPIO_rug1=8
GPIO_ONOFF=18
interval1 = 2
interval2 = 4
GPIO.setup(GPIO_ONOFF, GPIO.IN, pull_up_down=GPIO.PUD_UP)
done = False # loop control
timer = Event()
def quit_loop(): # Called by inbuilt threaded interrupt
global done
done = True
timer.set() # Interrupt the waiting
GPIO.add_event_detect(GPIO_ONOFF, GPIO.FALLING, callback=quit_loop, bouncetime=300) # Setup interrupt to call quit_loop
Because you're using this to break out of a loop, you want to shorten that loop to a single process:
tasks = [
(GPIO_nek, GPIO.LOW, interval1),
(GPIO_schouder, GPIO.LOW, interval1),
(GPIO_nek, GPIO.HIGH, interval1),
(GPIO_rug1, GPIO.LOW, interval2),
(GPIO_schouder, GPIO.HIGH, 0) ]
for pin, level, interval in tasks * 20: # Above you ran it 20 times, this notation keeps it in a single loop to break our o
if not done:
GPIO.digitalWrite(pin, level)
timer.wait(interval)
else:
timer.clear()
break
By using the threading Event().wait() and .set() instead of the standard time.sleep() you won't even have to wait for the sleep interval to finish.

raspberry pi python pwm continue after program done

I have a robot I am working on and am controlling it with PWM. The way I am controlling it is with a script that sets the PWM and then exits. I need it to set the PWM and then keep running. The reason I need it to exit is because I am just calling this script through an ssh connection each time the x and y values change. Normal digital outputs continue after the program exits but PWM doesn't with the way I have it setup.
Here is my code so far. It contains a lot of print statements to try to help me figure out what the problem was.
#filename: setMotors.py
import RPi.GPIO as GPIO
from sys import argv
from time import sleep
MOTOR_EN_1_PIN = 14
MOTOR_A_1_PIN = 15
MOTOR_B_1_PIN = 18
MOTOR_EN_2_PIN = 23
MOTOR_A_2_PIN = 24
MOTOR_B_2_PIN = 25
def mixXY(x, y):
"""
mixes x and y from a joystick to values for a 2 motor drive system
input: x (int or float), y (int or float)
output: (leftMotor (float), rightMotor (float)) tuple
"""
leftMotor = y + x
rightMotor = y - x
return (leftMotor, rightMotor)
def setMotorPWMS(leftMotor, rightMotor):
#left motor
if leftMotor == 0:
print("left motor 0")
GPIO.output(MOTOR_EN_1_PIN, 0)
motor1A.stop()
motor1B.stop()
elif leftMotor < 0:
print("left motor < 0")
GPIO.output(MOTOR_EN_1_PIN, 1)
motor1A.stop()
motor1B.ChangeDutyCycle(abs(leftMotor))
else:
print("left motor else")
GPIO.output(MOTOR_EN_1_PIN, 1)
motor1A.ChangeDutyCycle(leftMotor)
motor1B.stop()
#right motor
if rightMotor == 0:
print("right motor 0")
GPIO.output(MOTOR_EN_2_PIN, 0)
motor2A.stop()
motor2B.stop()
elif rightMotor < 0:
print("right motor < 0")
GPIO.output(MOTOR_EN_2_PIN, 1)
motor2A.stop()
motor2B.ChangeDutyCycle(abs(rightMotor))
else:
print("right motor else")
GPIO.output(MOTOR_EN_2_PIN, 1)
motor2A.ChangeDutyCycle(rightMotor)
motor2B.stop()
GPIO.setwarnings(False)
#setup
GPIO.setmode(GPIO.BCM)
GPIO.setup(MOTOR_EN_1_PIN, GPIO.OUT)
GPIO.setup(MOTOR_A_1_PIN, GPIO.OUT)
GPIO.setup(MOTOR_B_1_PIN, GPIO.OUT)
GPIO.setup(MOTOR_EN_2_PIN, GPIO.OUT)
GPIO.setup(MOTOR_A_2_PIN, GPIO.OUT)
GPIO.setup(MOTOR_B_2_PIN, GPIO.OUT)
motor1A = GPIO.PWM(MOTOR_A_1_PIN, 50)
motor1B = GPIO.PWM(MOTOR_B_1_PIN, 50)
motor2A = GPIO.PWM(MOTOR_A_2_PIN, 50)
motor2B = GPIO.PWM(MOTOR_B_2_PIN, 50)
motor1A.start(0)
motor1B.start(0)
motor2A.start(0)
motor2B.start(0)
if len(argv) <= 2:
print("Need to call with x and y from commandline")
else:
motorPWM = mixXY(int(argv[1]), int(argv[2]))
leftMotorPWM = motorPWM[0]
rightMotorPWM = motorPWM[1]
print("left motor:",leftMotorPWM)
print("right motor:", rightMotorPWM)
setMotorPWMS(leftMotorPWM, rightMotorPWM)
sleep(5)
print("done")
The way it would be called is with sudo python setMotors.py x y. Is there a way of keeping the PWM going after the program exits or a better way of doing this?

The RaspberryPi doesn't support hardware PWM, so it's emulated using a software loop. Basically, it sets the GPIO, sleeps a little, resets the GPIO, sleeps a little and loops. This is done in a separated thread which is killed when the program ends.
Thus, you have to find a way to keep your program alive in the background. If you look at the official example on use of PWM, you'll notice the endless loop that keeps the program alive until manually killed.
You should also add something like
try:
while 1:
time.sleep(0.5)
except KeyboardInterrupt:
pass
p.stop()
GPIO.cleanup()
to the end of your program, or something better constructed using the signal module.
Then, leave the process in the background before destroying the console
sudo python setMotors.py x y &
You could also let your program get daemonized.