<sxh [py][; options for SyntaxHighlighter]>
#!/usr/bin/python
# Written in Python 2.7


# Import required libraries
import sys
import time
import RPi.GPIO as GPIO

# Use BCM GPIO references
# instead of physical pin numbers
GPIO.setmode(GPIO.BCM)

# Define GPIO signals to use
# Physical pins 6,13,19,26
StepPins = [6,13,19,26]

# Set all pins as output
for pin in StepPins:
  print "Setup pins"
  GPIO.setup(pin,GPIO.OUT)
  GPIO.output(pin, False)

Seq = [[1,0,0,0],
       [1,1,0,0],
       [0,1,0,0],
       [0,1,1,0],
       [0,0,1,0],
       [0,0,1,1],
       [0,0,0,1],
       [1,0,0,1]]

       
StepCount = len(Seq)
StepDir = 1 # Set to 1 or 2 for clockwise
            # Set to -1 or -2 for anti-clockwise

# Read wait time from command line
if len(sys.argv)>1:
  WaitTime = int(sys.argv[1])/float(1000)
else:
  WaitTime = 10/float(1000)

# Initialise variables
StepCounter = 0

# Start main loop
while True:

#  print StepCounter,
#  print Seq[StepCounter]

  for pin in range(0,4):
    xpin=StepPins[pin]# Get GPIO
    if Seq[StepCounter][pin]!=0:
#      print " Enable GPIO %i" %(xpin)
      GPIO.output(xpin, True)
    else:
      GPIO.output(xpin, False)

  StepCounter += StepDir

  # If we reach the end of the sequence
  # start again
  if (StepCounter>=StepCount):
    StepCounter = 0
  if (StepCounter<0):
    StepCounter = StepCount+StepDir

  # Wait before moving on
  time.sleep(WaitTime)
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