使用Python代码更快的正交解码器循环 [英] Faster quadrature decoder loops with Python code

问题描述

我正在使用BeagleBone Black，并使用Adafruit的IO Python库.编写了一个简单的正交解码功能，当电动机以大约1800 RPM的速度运行时，它可以很好地工作. 但是，当电动机以较高速度运行时，代码开始缺少某些中断，并且编码器计数开始累积错误. 你们对我如何使代码更有效或者是否有一些函数可以使中断以更高的频率循环有任何建议.

I'm working with a BeagleBone Black and using Adafruit's IO Python library. Wrote a simple quadrature decoding function and it works perfectly fine when the motor runs at about 1800 RPM. But when the motor runs at higher speeds, the code starts missing some of the interrupts and the encoder counts start to accumulate errors. Do you guys have any suggestions as to how I can make the code more efficient or if there are functions which can cycle the interrupts at a higher frequency.

谢谢， 凯尔

代码如下:

# Define encoder count function
def encodercount(term):
global counts       
global Encoder_A
global Encoder_A_old
global Encoder_B
global Encoder_B_old
global error


Encoder_A = GPIO.input('P8_7')  # stores the value of the encoders at time of interrupt
Encoder_B = GPIO.input('P8_8')

if Encoder_A == Encoder_A_old and Encoder_B == Encoder_B_old:
# this will be an error
    error += 1
    print 'Error count is %s' %error

elif (Encoder_A == 1 and Encoder_B_old == 0) or (Encoder_A == 0 and Encoder_B_old == 1):
# this will be clockwise rotation
    counts += 1
    print 'Encoder count is %s' %counts
    print 'AB is %s %s' % (Encoder_A, Encoder_B)

elif (Encoder_A == 1 and Encoder_B_old == 1) or (Encoder_A == 0 and Encoder_B_old == 0):
# this will be counter-clockwise rotation
    counts -= 1
    print 'Encoder count is %s' %counts
    print 'AB is %s %s' % (Encoder_A, Encoder_B)

else:
#this will be an error as well
    error += 1
    print 'Error count is %s' %error

Encoder_A_old = Encoder_A     # store the current encoder values as old values to be used as comparison in the next loop
Encoder_B_old = Encoder_B       

# Initialize the interrupts - these trigger on the both the rising and falling 
GPIO.add_event_detect('P8_7', GPIO.BOTH, callback = encodercount)   # Encoder A
GPIO.add_event_detect('P8_8', GPIO.BOTH, callback = encodercount)   # Encoder B

# This is the part of the code which runs normally in the background
while True:
    time.sleep(1)

推荐答案

使代码更高效...

def encodercount(term):
global counts       
global Encoder_A
global Encoder_A_old
global Encoder_B
global Encoder_B_old
global error

Encoder_A,Encoder_B = GPIO.input('P8_7'),GPIO.input('P8_8')

if ((Encoder_A,Encoder_B_old) == (1,0)) or ((Encoder_A,Encoder_B_old) == (0,1)):
# this will be clockwise rotation
    counts += 1
    print 'Encoder count is %s\nAB is %s %s' % (counts, Encoder_A, Encoder_B)

elif ((Encoder_A,Encoder_B_old) == (1,1)) or ((Encoder_A,Encoder_B_old) == (0,0)):
# this will be counter-clockwise rotation
    counts -= 1
    print 'Encoder count is %s\nAB is %s %s' % (counts, Encoder_A, Encoder_B)

else:
#this will be an error
    error += 1
    print 'Error count is %s' %error

Encoder_A_old,Encoder_B_old = Encoder_A,Encoder_B

# Initialize the interrupts - these trigger on the both the rising and falling 
GPIO.add_event_detect('P8_7', GPIO.BOTH, callback = encodercount)   # Encoder A
GPIO.add_event_detect('P8_8', GPIO.BOTH, callback = encodercount)   # Encoder B

# This is the part of the code which runs normally in the background
while True:
    time.sleep(1)

最大的收益将来自print的单调用.通常，打印到stdout的速度很慢，这将限制程序的性能.您应该考虑仅每20次打印一次或更少一些.

The greatest benefit will come from the single call of print. Printing to the stdout is slow in general and this will limit the performance of your program. You should consider to print out only every 20th time or somewhat less often.

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