DevHeads IoT Integration Server•6mo ago

Issues with Accurate Quadrature Encoder Readings on BeagleBone Black

Hey guys am developing a real-time control system for a robotics application using a BeagleBone Black running Embedded Linux. The system needs to read data from a quadrature encoder to determine the position and speed of a motor. However, I encounter an issue where the encoder readings are not accurate or are missed at higher speeds. I have connected the quadrature encoder to the BeagleBone Black's GPIO pins, verified that the encoder signals (A and B) are properly connected to the correct GPIO pins. Error: Missed encoder pulses Here's my code

   import Adafruit_BBIO.GPIO as GPIO
   import time

   # Encoder GPIO pins
   ENCODER_A = "P8_12"
   ENCODER_B = "P8_14"

   # Initialize encoder position
   position = 0

   def encoder_callback(channel):
       global position
       if GPIO.input(ENCODER_A) == GPIO.input(ENCODER_B):
           position += 1
       else:
           position -= 1

   # Setup GPIO pins
   GPIO.setup(ENCODER_A, GPIO.IN)
   GPIO.setup(ENCODER_B, GPIO.IN)

   # Add event detection for encoder A pin
   GPIO.add_event_detect(ENCODER_A, GPIO.BOTH, callback=encoder_callback)

   try:
       while True:
           print(f"Encoder position: {position}")
           time.sleep(0.1)

   except KeyboardInterrupt:
       print("\nExiting...")

   finally:
       GPIO.cleanup()

   import Adafruit_BBIO.GPIO as GPIO
   import time

   # Encoder GPIO pins
   ENCODER_A = "P8_12"
   ENCODER_B = "P8_14"

   # Initialize encoder position
   position = 0

   def encoder_callback(channel):
       global position
       if GPIO.input(ENCODER_A) == GPIO.input(ENCODER_B):
           position += 1
       else:
           position -= 1

   # Setup GPIO pins
   GPIO.setup(ENCODER_A, GPIO.IN)
   GPIO.setup(ENCODER_B, GPIO.IN)

   # Add event detection for encoder A pin
   GPIO.add_event_detect(ENCODER_A, GPIO.BOTH, callback=encoder_callback)

   try:
       while True:
           print(f"Encoder position: {position}")
           time.sleep(0.1)

   except KeyboardInterrupt:
       print("\nExiting...")

   finally:
       GPIO.cleanup()

@Middleware & OS

1 Reply

Renuel Roberts•5mo ago

The issue with missed encoder pulses at higher speeds might be the limitations of using GPIO polling or interrupts in a non-real-time environment like Embedded Linux, at higher speeds, the encoder generates pulses faster than the CPU can handle, especially if other processes are running, leading to missed counts.

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Issues with Accurate Quadrature Encoder Readings on BeagleBone Black