PRE2017 3 11 Python Code

From Control Systems Technology Group

Import required packages

#!/usr/bin/python
from pyzbar.pyzbar import decode	# QR reader
from PIL import Image               	# Image reader
import cv2                     		# Image reader
import RPi.GPIO as GPIO    	     	# GPIO pin control
import time               	 	# Posibility to delay
import signal				# Cleanup when ending script
import sys				# Needed to stop script if no camera

Set up constants

pin_s1  = 29		# Continuous servo 1
pin_s2  = 33            # Continuous servo 2
freq 	= 50        	# Continuous servo frequency [Hz]

s1left   = 5.00         # 100% velocity to left
s1center = 6.70         # no movement
s1right  = 8.00         # 100% velocity to right

s2left   = 5.00         # 100% velocity to left
s2center = 6.60         # no movement
s2right  = 8.00         # 100% velocity to right

cyldelay      = 2 	# Time it takes for cylinder to rotate
dropdelay     = 5    	# Time it takes to drop package
pauzedelay    = 2 	# Time between cylinder rotation and platform movement
platformdelay = 2     	# Time it takes for platform to move down

imgname = "image2.jpg"  # File frame is temporarily saved in

# Imports allowed QRcodes
passcodelist = []
with open("authcodes") as file:
	passcodelist = [line.strip() for line in file]

Stops the script safely if CTRL+C is pressed

# Releases pins when script is interrupted
def end_run(signal,frame):
	global running
	print("Ctrl+C captured, ending script")
	running = False
	servo1.stop()
	servo2.stop()
	GPIO.cleanup()

# Runs end_run if ctrl+C is clicked
signal.signal(signal.SIGINT, end_run)

Takes a picture with the camera

# Takes picture from camera, reads and evaluates QRcode
def QRscanner(passcodelist, camslot):
	camera = cv2.VideoCapture(camslot)	# Initializes camera viewer
	grabbed, im = camera.read()     	# Reads figure

Checks if a picture is taken, and if it is not, it looks for other cameras or stops the script

	if not grabbed:				# Searches for working camera
		if camslot < 5:
			camstr = "No camera connected in slot: " + str(camslot)
			print(camstr)
			camslot = camslot + 1
			return False, camslot
		else:
			print("No camera connected")
			servo1.stop()
			servo2.stop()
			GPIO.cleanup()
			sys.exit()

Reads QR-codes in the image and checks if a correct code is presented

	cv2.imwrite(imgname,im)		# Converts image to jpg
	img = Image.open(imgname)	# Reads jpg
	decodedObjects = decode(img)    # Decodes image
	for obj in decodedObjects:     	# Makes sure every code is read
	   	qrdata = obj.data       # Reads the alphanumerical code
		for passcode in passcodelist:
    			if passcode in qrdata:      # Verifies if code is legit
				print("Correct code, cylinders start opening")
        			return True, camslot
			else:
				print("Wrong code")
	return False, camslot

Sets up the output pins that control the servos

GPIO.setmode(GPIO.BOARD)    	# Board numbering sceme pins
GPIO.setup(pin_s1, GPIO.OUT)	# Sets pins as output
GPIO.setup(pin_s2, GPIO.OUT)
servo1 = GPIO.PWM(pin_s1, freq)	# Assigns frequency to pins
servo2 = GPIO.PWM(pin_s2, freq)
servo1.start(s1center)		# Starts servos in neutral position
servo2.start(s2center)

Sets up variables, starts the script, and runs the QR-code reader until correct code is presented or CTRL+C is pressed

camslot = 0 		# Default camera slot
running = True
print("Program Running, provide QR-code")

while running:
	rightcode, camslot = QRscanner(passcodelist, camslot)  # Runs QR-reader

Makes Cylinders and platform move if the correct code is presented

	if rightcode:
		servo1.ChangeDutyCycle(s1left)	 # Cylinders open
    		time.sleep(cyldelay)             # Duration of cylinder movement
    		servo1.ChangeDutyCycle(s1center) # Cylinders stop moving
		print("Cylinders are open, package can be dropped")
    		time.sleep(dropdelay)            # Duration of package dropping
    		print("Package dropped, cylinders start closing")
		servo1.ChangeDutyCycle(s1right)  # Cylinders close
   		time.sleep(cyldelay)             # Duration of cylinder movement
    		servo1.ChangeDutyCycle(s1center) # Cylinders stop moving
		print("Cylinders are closed")
		time.sleep(pauzedelay)           # Time buffer
		print("Platform starts moving down")
		servo2.ChangeDutyCycle(s2left)   # Platform moves down
    		time.sleep(platformdelay)        # Duration of platform movement
    		servo2.ChangeDutyCycle(s2center) # Platform stops moving
		print("Platform stopped moving down, new code can be scanned")