Package: pydynamixel
A Python library for controlling Dynamixel servos.InstallationThis package requires pyserial, whicah can be installed using:pip install pyserialor, using another method described on the documentation page:http://pythonhosted.org//pyserial/pyserial.html#installationThe PyDynamixel package itself can be installed using pip:pip install pydynamixelThe source code (with examples) is available from the GitHub repository:https://github.com/richard-clark/pydynamixelIt can also be installed by cloning into the source and runningsetup.py:git clone https://github.com/richard-clark/pydynamixel
cd pydynamixel
python setup.py installCommunicationTheget_serial_for_urlmethod can be used to get aserialobject correctly
configured for the specified url (on POSIX systems; Windows users can useget_serial_for_com).By default, Dynamixels comminate at a high baud rate (1,000,000 baud), and use a single-wire
protocol. This combination is highly susceptible to noise. For this reason, thewrite_and_get_responsemultiple function is recommended as the preferred way of commincating
with the Dynamixel. This function will make multiple arguments to clear the serial port, send the
packet, and read a valid response before failing.Servo InitializationThe first time that a servo is instructed to move to a specified position after it has been
powered up, it will do so at the maximum speed possible, regardless of whether the velocity
has been set. This is dangerous, as the servos are quite powerful.This issue can be mitigated by first reading the current position of the servo, and then
commanding the servo to move to that same position. Theinit()method performs this function.Basic LED ExampleThe AX-18A servos have integrated LEDs. By default, these LEDs are off. The following code
can be used to turn on the LED on a connected servo (on POSIX-compliant platforms,
such as Linux and OSX).from pydynamixel import dynamixel, registers

# You'll need to change this to the serial port of your USB2Dynamixel
serial_port = '/dev/tty.usbserial-A921X77J'

# You'll need to change this to the ID of your servo
servo_id = 9

# Turn the LED on
led_value = dynamixel.registers.LED_STATE.ON

try:
    ser = dynamixel.get_serial_for_url(serial_port)
    dynamixel.set_led(ser, servo_id, led_value)
    print('LED set successfully!')
except Exception as e:
    print('Unable to set LED.')
    print(e)To perform the same function on Windows, use the following:from pydynamixel import dynamixel, registers

# You'll need to change this to the serial port of your USB2Dynamixel
com_port = 'COM5'

# You'll need to change this to the ID of your servo
servo_id = 9

# Turn the LED on
led_value = dynamixel.registers.LED_STATE.ON

try:
    ser = dynamixel.get_serial_for_url(serial_port)
    dynamixel.set_led(ser, servo_id, led_value)
    print('LED set successfully!')
except Exception as e:
    print('Unable to set LED.')
    print(e)Motion ExampleThis example simply moves a specified servo to a specified position.from pydynamixel import dynamixel

# You'll need to change this to the serial port of your USB2Dynamixel
serial_port = '/dev/tty.usbserial-A921X77J'

# You'll need to modify these for your setup
servo_id = 9
target_position = 768 # (range: 0 to 1023)

# If this is the first time the robot was powered on,
# you'll need to read and set the current position.
# (See the documentation above.)
first_move = True

try:
    ser = dynamixel.get_serial_for_url(serial_port)

    if first_move == True:
        dynamixel.init(ser, servo_id)

    dynamixel.set_position(ser, servo_id, target_position)
    dynamixel.send_action_packet(ser)

    print('Success!')

except Exception as e:
    print('Unable to move to desired position.')
    print(e)Chain ModuleMultiple servos can be controlled more easily using the chain module.The following example demonstrates the process of manipulating the robot
using a series of frames using the same velocity for each servo. Each item
inposcontains a list of positions, each one corresponding with a
servo id. After instructing each joint to move to the specified position,
the program waits until alls ervos have finished moving before moving to the
next frame.from pydynamixel import chain, dynamixel

servo_ids = [1, 2, 3, 4, 5, 6, 7]
velocity = 180

# Initialize the servos
chain.init(ser, servo_ids, velocity)

# A list of frames each consisting of the target
# displacements for each joint
pos = [[822, 94, 929, 919, 104, 820, 691],
    [822, 632, 391, 919, 104, 523, 561],
    [822, 640, 383, 911, 112, 516, 650],
    [822, 100, 923, 918, 105, 538, 650],
    [818, 100, 923, 918, 105, 538, 650],
    [495, 100, 923, 918, 105, 538, 650],
    [495, 714, 309, 802, 221, 538, 650],
    [495, 723, 300, 791, 232, 538, 569],
    [495, 103, 920, 916, 107, 538, 571],
    [495, 103, 920, 916, 107, 538, 571],
    [495, 723, 300, 791, 232, 538, 569],
    [495, 714, 309, 802, 221, 538, 650],
    [495, 100, 923, 918, 105, 538, 650],
    [818, 100, 923, 918, 105, 538, 650],
    [822, 100, 923, 918, 105, 538, 650],
    [822, 640, 383, 911, 112, 516, 650],
    [822, 632, 391, 919, 104, 523, 561],
    [822, 94, 929, 919, 104, 820, 691]]

# Iterate over the vectors, move to each,
# and wait for each move to complete
for v in pos:
    vector = chain.make_vector_constant_velocity(v, servo_ids, velocity)
    chain.move_to_vector(ser, vector)
    chain.wait_for_move(ser, joints)Fore each vector, after instructing the joints to move to the specified position,
the program waits until all servos have finished moving before moving to the next frame.Further DocumentationFor further documentation, seehttp://richard-h-clark.com/tag/pydynamixel