DynamixelController

Python controller interface with improved buck reading and writing for faster communication rate and lower latency.

Source of communication bottleneck

1. High USB latency time.

   There might be a default USB latency time limiting the communication frequency with USB devices (16 ms for example in Ubuntu 18.04). For more information please refere to https://emanual.robotis.com/docs/en/software/dynamixel/dynamixel_wizard2/#usb-latency-setting.

   To change the latency time on ubuntu (replace "ttyUSB0" with your device name):

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

   To manaully change the latency time on ubuntu:

   echo 1 | sudo tee /sys/bus/usb-serial/devices/ttyUSB0/latency_timer

   NOTE: You have to set the latency time every time you plug you USB device.

2. Low baudrate of Dynamixel bus.

   Change the baudrate of dynamixel actuators to a higher value (4M or higher)

Pre-requests

1. The package is tested and targeted to run only on ubuntu. (tested on Ubuntu 18.04)

2. Download dynamixel_sdk source code (we use develop branch to take the advantage of fast sync read/write):

   git clone https://github.com/ROBOTIS-GIT/DynamixelSDK/tree/develop

3. Navigate to DynamixelSDK/python/src.

4. Open the file "port_handler.py". In line 27, change the variable LATENCY_TIMER to the USB latency time you set.

   LATENCY_TIMER = 16 # Change the value to the USB latency time

   Note: This only changes the timeout of the port_handler. If not properly set, the default timeout will be longer and may cause problems with a high communication frequency.

5. Navigate to DynamixelSDK/python. Install the modified package by running:

   python3 setup.py install

Install the package

pip install -i https://test.pypi.org/simple/ dynamixel-controller==0.0.12