Loop not going back to 0

[DRPi5]

Hello, I am trying to get a PID working, but I am struggling at one part of the code. What I want is to get the second while loop to run for 0.5 sec and then restart the readings of my encoder. At this point, the readings from my encoder keeps increasing, they do not go back to 0 after 0.5sec. Because of that my RPM calculations are not coming out as desired.

How can I reset the value of my encoder to 0 after 0.5 sec and go again through the loop?

The Implementation part of the PID I think I got it, but I need to get the proper readings from my encoder in order to implement it. Here is the code.

Also the calculation for the RPM I need to take them out of the loop, so the RPM will be calculated only for the value of counter at 0.5sec and not for all the readings, that way I will reduce the processing in my code.

Code: Select all

import RPi.GPIO as GPIO
import time

# GPIO Setup
GPIO.setmode(GPIO.BOARD)
GPIO.setwarnings(False)

# Pin Setup (change only fwd and bwd pins for both the motors)
Afwd_pin = 38
Abwd_pin = 40

Bfwd_pin = 37
Bbwd_pin = 35

enc_Al_pin = 11
enc_Ar_pin = 13

enc_Bl_pin = 29
enc_Br_pin = 31

# GPIO.out settings (Don't change anything)
GPIO.setup(Afwd_pin, GPIO.OUT)
GPIO.setup(Abwd_pin, GPIO.OUT)

GPIO.setup(enc_Al_pin, GPIO.IN)
GPIO.setup(enc_Ar_pin, GPIO.IN)

GPIO.setup(Bfwd_pin, GPIO.OUT)
GPIO.setup(Bbwd_pin, GPIO.OUT)

GPIO.setup(enc_Bl_pin, GPIO.IN)
GPIO.setup(enc_Br_pin, GPIO.IN)

# Set variables for fwd and bwd
Afwd = GPIO.PWM(Afwd_pin,100)
Abwd = GPIO.PWM(Abwd_pin,100)

Bfwd = GPIO.PWM(Bfwd_pin,100)
Bbwd = GPIO.PWM(Bbwd_pin,100)

# Initialize (Don't change anything)
Afwd.start(0)
Abwd.start(0)

Bfwd.start(0)
Bbwd.start(0)
        
# Loop to make the robot move forward
''' We run the code for 5 seconds. Period is the time that we have to run it for'''
start = time.time()
period = 0.5

last_AA = 0b00
last_BB = 0b00
counter_A = 0
counter_B = 0

outcome = [0,-1,1,0,-1,0,0,1,1,0,0,-1,0,-1,1,0]

# Run motor
Afwd.ChangeDutyCycle(80)
Bfwd.ChangeDutyCycle(80)

''' The ChangeDutyCycle() makes the motors rotate at that speed '''
try:
    while True:
      # Encoder reading
      left_A = GPIO.input(enc_Al_pin)
      right_A = GPIO.input(enc_Ar_pin)
      left_B = GPIO.input(enc_Bl_pin)
      right_B = GPIO.input(enc_Br_pin)
 
        
      while True:
        current_aa = (left_A << 1) | right_A
        position = (last_AA << 2) | current_aa
        counter_A += outcome[position]
        last_AA = current_aa
        print('A = ', counter_A)
        
        current_bb = (left_B << 1) | right_B
        position = (last_BB << 2) | current_bb
        counter_B += outcome[position]
        last_BB = current_bb
        print('B = ', counter_B)
        
        # stop loop in time = period
        if time.time() > start + period : break
              

      #print('final counter of A = ', counter_A)
      #print('final counter of B = ', counter_B)

      # RPM calculation
      RPM_A = ((counter_A*60/682.4)/0.5)
      print('RPM_A = ', RPM_A)
      
      RPM_B = ((counter_B*60/682.4)/0.5)
      print('RPM_B = ', RPM_B)
         
    
except KeyboardInterrupt:
    pass

# Error and PID implementation

# Stop commands to run (Don't change anything)
Afwd.stop()
Abwd.stop()
Bfwd.stop()
Bbwd.stop()

GPIO.cleanup()

[pcmanbob]

I don't see how you ever expect to run the second while true loop .

the first while true loop will run for ever reading your inputs so you will never run the second while true loop.

I think what you need to do is read your inputs for a set amount time then run the calculations and at then end of the calculations reset your input variables that are recording your encoders values.

some thing like this

Code: Select all

while True:  # main loop

	# reset encoders
	
	while time < 5 :  # reads encoders for 5 seconds
	
		# read encoders
		
	#do calculations

        #loop ends here so restarts main loop
        

[DRPi5]

I don't see how you ever expect to run the second while true loop .

the first while true loop will run for ever reading your inputs so you will never run the second while true loop.

I think what you need to do is read your inputs for a set amount time then run the calculations and at then end of the calculations reset your input variables that are recording your encoders values.

some thing like this

Code: Select all

while True:  # main loop

	# reset encoders
	
	while time < 5 :  # reads encoders for 5 seconds
	
		# read encoders
		
	#do calculations

        #loop ends here so restarts main loop
        

I am new with Python, so many things are difficult for me at this time, I am struggling with the loops that is why I was so confused and did not know why I was getting those results.

I will try this on my code and will see how it goes. I appreciate your help.