PyDynamixel_v2

Python interface to the Dynamixel protocol. Supports both Protocols 1 and 2 using Dynamixel SDK python library.

Requirements

PySerial:

pip install pyserial

Dynamixel SDK:

git clone https://github.com/ROBOTIS-GIT/DynamixelSDK
cd python
python setup.py install

Before Usage - Maximize reading and writing speed

Give USB port permissions.

sudo chown username /dev/ttyUSB0

Set it to low_latency (1ms, instead of default 16ms)

setserial /dev/ttyUSB0 low_latency

Check if it worked.

cat /sys/bus/usb-serial/devices/ttyUSB0/latency_timer

Usage and Examples

To install the module simply run

python setup.py install

The control tables for each motor, describing addresses and lengths are in DynamixelControlTables.py. The only motors implemented right now are MX-28 (for Protocol 1.0 and 2.0) and RH8D hand from Seed robotics (Protocol 1.0). If you want to add more motors just edit that file referencing the Dynamixel manuals and add the entry to the ctrltables_str_mappings variable. The Sync and Bulk operations will only work if all motors attached to the port have the same control table.

Instantiating a single MX28 with Protocol 1.0 and reading present position:

import PyDynamixel as pd

# Parameters
baudnum = 1 # baudrate is calculated as 2Mbps / (baudnum+1)
protocol_version = 1
motor_id = 10

# Create the port object
port = pd.DxlComm("/dev/ttyUSB0", baudnum=baudnum, protocol_version=protocol_version)
# Create the joint object. Control table for MX28 Protocol 1.0
joint = pd.Joint(motor_id, control_table="MX28-1")

# Attach joint to port
port.attach_joint(joint)

# Read current angle
curr_angle = joint.get_angle()
print(f"[{motor_id}]: {curr_angle:.2f}")

Instantiating a single MX28 with Protocol 2.0 and reading present position:

import PyDynamixel as pd

# Parameters
baudnum = 1 # baudrate is calculated as 2Mbps / (baudnum+1)
protocol_version = 2
motor_id = 10

# Create the port object
port = pd.DxlComm("/dev/ttyUSB0", baudnum=baudnum, protocol_version=protocol_version)

# Create the joint object. Control table for MX28 Protocol 2.0
joint = pd.Joint(motor_id, control_table="MX28-2")

# Attach joint to port
port.attach_joint(joint)

# Read current angle
curr_angle = joint.get_angle()
print(f"[{motor_id}]: {curr_angle:.2f}")

Instantiating several MX28 Protocol 1.0 and reading present position sequentially:

import PyDynamixel as pd

# Parameters
baudnum = 1 # baudrate is calculated as 2Mbps / (baudnum+1)
protocol_version = 1

# Create the port object
port = pd.DxlComm("/dev/ttyUSB0", baudnum=baudnum, protocol_version=protocol_version)

# Use this so you don't need to specify it every time Joint() is called
pd.setDefaultCtrlTable("MX28-1")
joints = [pd.Joint(1), pd.Joint(2), pd.Joint(3), pd.Joint(4)]

port.attach_joints(joints)

for joint in joints:
    curr_angle = joint.get_angle()
    print(f"[{joint.servo_id}]: {curr_angle:.2f}")

Instantiating several MX28 Protocol 1.0 and performing bulk read for present position:

import PyDynamixel as pd

# Parameters
baudnum = 1 # baudrate is calculated as 2Mbps / (baudnum+1)
protocol_version = 1

# Create the port object
port = pd.DxlComm("/dev/ttyUSB0", baudnum=baudnum, protocol_version=protocol_version)

# Use this so you don't need to specify it every time Joint() is called
pd.setDefaultCtrlTable("MX28-1")
joints = [pd.Joint(1), pd.Joint(2), pd.Joint(3), pd.Joint(4)]

port.attach_joints(joints)

# Bulk read joints 1 and 2
angles = port.bulk_read_present_position(ids=[1, 2])
print(angles)

# Bulk read all attached joints
angles = port.bulk_read_present_position()
print(angles)

Instantiating several MX28 Protocol 1.0 and performing sync write of goal position:

import PyDynamixel as pd

# Parameters
baudnum = 1 # baudrate is calculated as 2Mbps / (baudnum+1)
protocol_version = 1

# Create the port object
port = pd.DxlComm("/dev/ttyUSB0", baudnum=baudnum, protocol_version=protocol_version)

# Use this so you don't need to specify it every time Joint() is called
pd.setDefaultCtrlTable("MX28-1")
port.attach_joints([pd.Joint(1), pd.Joint(2), pd.Joint(3), pd.Joint(4), pd.Joint(5)])

# Set goal value in joint object. This does NOT send any messages, just changes
# value of the object in memory
for j in port.joints:
    j.set_goal_value(3.14)

# Sends the goal_value of each joint object to the actual motors
port.sync_write_goal_position()

guichristmann/PyDynamixel_v2