使用Python代码加速二次解码器循环

Question

我正在使用BeagleBone Black，并且在用Adafruit的IO Python库。写了一个简单的四分频解码函数，当电机以大约1800转每分钟的速度运行时，它工作得很好。

但是，当电机速度更高时，代码开始漏掉一些中断，编码器的计数开始出现错误。

你们有没有什么建议，可以让我代码更高效，或者有没有什么函数可以让中断以更高的频率循环？

谢谢，

Kel

这是代码：

# 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)

Answer 1

让代码更高效...

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)

最大的好处来自于只调用一次 print。一般来说，打印到 stdout（标准输出）是比较慢的，这会影响你程序的运行速度。你可以考虑每隔20次才打印一次，或者更少一些。