scrap of motor code from server.py

motor.py

# Mostly originally written by Richard Klancer.

# Licensed under MIT license: http://opensource.org/licenses/MIT

class Motor:
  SERIAL_SPEED = 115200
  TIMEOUT_INTERVAL = 3

  def __init__(self):
    import time
    self.last_command_string = ""
    self.last_command_time = time.time()
    self.timed_out = False


  def send_command_string(self, command_string):
    import pytronics
    
    self.last_command_string = command_string
    pytronics.serialWrite(command_string, self.__class__.SERIAL_SPEED)
    print command_string


  def repeat_last_command_or_time_out(self):
    import time

    now = time.time()
    if (now - self.last_command_time) > self.__class__.TIMEOUT_INTERVAL:
      self.timed_out = True
      return

    self.send_command_string(self.last_command_string)     


  def send_command(self, left, right):
    import time

    if (abs(left) > 1000) or (abs(right) > 1000):
      raise ValueError("Motor command out of range")

    self.last_command_time = time.time()
    self.timed_out = False

    command_string = "!M %d %d\r" % (-right, left)
    self.send_command_string(command_string)


def interpret_joystick_command(x, y):
  """Accepts a joystick position (x, y) where x and y represent a point within the unit circle.
     Returns a tuple (left, right) of the corresponding motor speeds for a left and right motor in
     a differential drive setup. For convenient use with the MDC2200, left and right are integers 
     in the range -1000..1000"""

  from math import atan2, sin, cos, pi, sqrt
  angle = atan2(y, x) - pi/4

  # interpret the distance from the
  speed = sqrt(x*x + y*y)
  if speed > 1.0:
    raise ValueError("Joystick input outside the unit circle")
  
  left = sin(angle)
  right = cos(angle)
  # scale the motor speeds so that, if the joystick is pushed to its maximum distance from the
  # center, the faster motor is at max speed regardless of the angle
  scale = 1000 * speed / max(abs(left), abs(right))
  return (int(scale * left + 0.5), int(scale * right + 0.5))


motor = Motor()

@public.route('/joystick', methods=['POST'])
def joystick():
  x = float(request.form['x'])
  y = float(request.form['y'])
  motor.send_command(*interpret_joystick_command(x, y))
  return "ok"

@rbtimer(1)
def repeat_last_motor_command_or_time_out(num):
  motor.repeat_last_command_or_time_out()


@public.route('/forward', methods=['POST'])
def forward():
    import pytronics
    pytronics.serialWrite('!M -750 750\r', speed=115200)
    return 'Tried to move motors'

@public.route('/back', methods=['POST'])
def back():
    import pytronics
    pytronics.serialWrite('!M 750 -750\r', speed=115200)
    return 'Tried to move motors'

@public.route('/left', methods=['POST'])
def left():
    import pytronics
    pytronics.serialWrite('!M 750 750\r', speed=115200)
    return 'Tried to move motors'

@public.route('/right', methods=['POST'])
def right():
    import pytronics
    pytronics.serialWrite('!M -750 -750\r', speed=115200)
    return 'Tried to move motors'

@public.route('/stop', methods=['POST'])
def stop():
    import pytronics
    pytronics.serialWrite('!M 0 0\r', speed=115200)
    return 'Tried to move motors'