adds stepper library with an example

examples/Stepper_knob.py

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+#!/usr/bin/env python
+"""
+ Stepper_knob.py
+ Alaa Agwa - 3/3/2014
+
+ An example use of PyBBIO's stepper motor follows the turns of a potentiometer
+ (or other sensor) on analog input 0.
+
+ Based on Arduino's Servo library example:
+  http://arduino.cc/en/Tutorial/MotorKnob
+
+
+
+ This example is in the public domain.
+"""
+
+# First we must import PyBBIO: 
+from bbio import *
+# Then we can import Stepper:
+from Stepper import *
+
+import time
+start_time = time.time() 
+
+stepper = Stepper(GPIO01_17,GPIO03_21,GPIO03_19,GPIO03_15,100)
+
+def setup():
+	stepper.setSpeed(30);
+
+def loop():
+	#get the sensor value
+	val = analogRead(0)
+
+	#move a number of steps equal to the change in the
+	#sensor reading
+	stepper.step(val - previous , start_time)
+
+	#remember the previous value of the sensor
+	previous = val
+
+run(setup, loop)

libraries/Stepper/README

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+Stepper - v0.1
+
+Copyright 2012 Alexander Hiam
+agwatic@gmail.com
+
+Library for controlling stepper motors with the BeagleBone's pins.
+
+See documentation here:
+
+As well as the included example programs:
+ PyBBIO/examples/Stepper_knob.py
+
+Based on the Arduino Servo library:
+ http://www.arduino.cc/en/Reference/Stepper
+
+Servo is released as part of PyBBIO under its Apache 2.0 license.
+See PyBBIO/LICENSE.txt

libraries/Stepper/Stepper.py

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+"""
+ Stepper - v0.1
+ Copyright 2014 Alaa Agwa
+
+ Library for controlling stepper motors.
+
+ The sequence of control signals for 4 control wires is as follows:
+
+  Step C0 C1 C2 C3
+     1  1  0  1  0
+     2  0  1  1  0
+     3  0  1  0  1
+     4  1  0  0  1
+
+  The sequence of controls signals for 2 control wires is as follows
+  (columns C1 and C2 from above):
+
+  Step C0 C1
+     1  0  1
+     2  1  1
+     3  1  0
+     4  0  0
+"""
+from bbio import *
+
+
+class Stepper(object):
+	def __init__(self,steps = 100 , pin_1, pin_2, pin_3=None, pin_4=None):
+		self.step_number = 0	# which step the motor is on
+		self.speed = 0			# the motor speed, in revolutions per minute
+		self.direction = 0		# motor direction
+		self.last_step_time = 0 # time stamp in ms of the last step taken
+		self.number_of_steps = setps # total number of steps for this motor
+
+		# Pins for the motor control connection
+		self.motor_pin1 = pin_1
+		self.motor_pin2 = pin_2
+		self.motor_pin3 = pin_3
+		self.motor_pin4 = pin_4
+
+		#setup the pins
+		pinMode(self.motor_pin1,OUTPUT)
+		pinMode(self.motor_pin2,OUTPUT)
+		pinMode(self.motor_pin3,OUTPUT)
+		pinMode(self.motor_pin4,OUTPUT)
+
+		#pins count the stepMotor() method
+		if(self.motor_pin3 == None and self.motor_pin4 == None):
+			self.motor_pins = 2
+		elif(self.motor_pin3 != None and self.motor_pin4 != None):
+			self.motor_pins = 4
+
+
+
+	#Sets the speed in revs per minute
+	def setSpeed(self , whatSpeed):
+		self.step_delay = 60L * 1000L / self.number_of_steps / whatSpeed
+
+
+
+	"""
+	Moves the motor steps_to_move steps.  If the number is negative, 
+    the motor moves in the reverse direction.
+	"""
+	def step(self,steps_to_move,start_time):
+		steps_left = abs(steps_to_move) #how many steps to take
+
+		#determine direction based on whether steps_to_mode is + or -
+
+		if(steps_to_move>0):
+			self.direction = 1
+		elif(steps_to_move<0):
+			self.direction=0
+
+		#decrement the number of steps, moving one step each time
+		while(steps_left >0):
+			#move only if the appropriate delay has passed
+			if(((start_time*1000) - self.last_step_time) >= self.step_delay):
+				self.last_step_time = start_time*1000
+
+				#increment or decrement the step number, depending on direction
+				if(self.direction == 1):
+					self.step_number +=1
+					if(self.step_number == self.number_of_steps):
+						self.step_number = 0
+				else:
+					if(self.step_number == 0):
+						self.step_number = self.number_of_steps
+
+					self.step_number -=1
+			#decrement the steps left
+			steps_left -=1
+			#step the motor to step number 0, 1, 2, or 3
+			stepMotor(self.step_number %4)
+
+	"""
+
+	Moves the motor forward or backwards.
+
+	"""
+	def stepMotor(self,thisStep):
+		if(self.motor_pins == 2):
+			if(thisStep == 0): # 01
+				digitalWrite(self.motor_pin1,LOW)
+				digitalWrite(self.motor_pin2,HIGH)
+			elif(thisStep == 1): # 11 
+				digitalWrite(self.motor_pin1,HIGH)
+				digitalWrite(self.motor_pin2,HIGH)
+			elif(thisStep == 2): # 10
+				digitalWrite(self.motor_pin1,HIGH)
+				digitalWrite(self.motor_pin2,LOW)
+			elif(thisStep == 3): # 00 
+				digitalWrite(self.motor_pin1,LOW)
+				digitalWrite(self.motor_pin2,LOW)
+
+		elif(self.motor_pins == 4):
+			if(thisStep == 0): # 1010
+				digitalWrite(self.motor_pin1,HIGH)
+				digitalWrite(self.motor_pin2,LOW)
+				digitalWrite(self.motor_pin3,HIGH)
+				digitalWrite(self.motor_pin4,LOW)
+			elif(thisStep == 1): #  0110
+				digitalWrite(self.motor_pin1,LOW)
+				digitalWrite(self.motor_pin2,HIGH)
+				digitalWrite(self.motor_pin3,HIGH)
+				digitalWrite(self.motor_pin4,LOW)
+			elif(thisStep == 2): # 0101
+				digitalWrite(self.motor_pin1,LOW)
+				digitalWrite(self.motor_pin2,HIGH)
+				digitalWrite(self.motor_pin3,LOW)
+				digitalWrite(self.motor_pin4,HIGH)
+			elif(thisStep == 3): # 1001
+				digitalWrite(self.motor_pin1,HIGH)
+				digitalWrite(self.motor_pin2,LOW)
+				digitalWrite(self.motor_pin3,LOW)
+				digitalWrite(self.motor_pin4,HIGH)
+
+
+
+
+

libraries/Stepper/__init__.py

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+# __init__.py for Stepper
+
+from Stepper import *