Dynamixel

Dynamixel offers a varity of controlable motors to be used for small robots and manipulators.

Dynamixel is used many places - among them ithe the the educational crustcrawler manipulator.

Dynamixel motors short

• rs485 based fieldbus

• uses own protocol stack: Protocol 1 and Protocol 2

• linux, mac and windows wizard program

Interesting topics

1. Serial communication

   1. rs232 - point to point

   2. rs485 - multi drop

2. Serial protocols

   1. Dynamixel protocols

3. Arduino setup

4. setup and handling of the CrustCrawler form a communication point of view

RS232 and RS485l

• rs232 explained

• rs485 explained

Tutorials for RS485

• tutorial 1

• a small video

protocols

• Dynamixel protocol 1

  • org link

• Dynamixel protocol 2

  • org link

• CRC calculations

  • org link

The MX64 motor

• mx64.pdf

• org

Dynamixel example code

We have som code snippets for protocol no 2 for the MX64

• lectrs485dynamixeldyncode.html

• as zip file (3 examples)

• dynamixel rs485 shield

RS 485 design

• Designing rs485

• https://en.wikipedia.org/wiki/RS-485

• TI design guide

RS485 troble shooting

• http://www.windmill.co.uk/rs485.html

• https://www.sparkfun.com/tutorials/215

• http://ltxfaq.custhelp.com/app/answers/detail/a_id/480/~/troubleshooting-rs485-connections

• https://electronics.stackexchange.com/questions/242011/termination-resistor-creating-communication-problem-in-rs485-modbus-tcp

  • just oversee MODBUS word

• MX64 register overview

• w250 motor used on turtlebot 3 Burger

EMG XBEE protocol

• emg protocol

Slides

• is here

Exercises

We all ned to be in control of our wiring.

RS485 consists of

• a pair of signal wires (see RS485 links above)

• a way ot either

  • have common ground

  • avoid common ground by galvanic insolation (not case in our lab)

• So you need to have TX, RX,GND from your Arduino to the red Sparkfun rs232 to rs485 board

  • check and double check that ( I have seen smoky devices from you the last week)

2)

Start loking at the CC protocol 2 for use in your project

Suggested mini project testing

• Dynamixel motor

  • protocol 2

  • arduino as master on rs485

  • you code shall be easy to change motor ID ( we will announce ID of our motor present at examine)

  • identify address for one of your motors

• design, implement, test and explain

  • reset command (for all motors ?!?)

  • enable/disable torques on dyn motor (command addr 24)

  • set P-gain once (meaning not every time in your loop)

  • With a fixed samplingsfreq (10 Hz) you shall

    • get present temperature and reset or stop motor is temperature is to .high

“THE BEER-WARE LICE NSE” (Revision 42): jensd@jensd.dk wrote this file. As long as you retain this notice you can do whatever you want with this stuff on these pages. If we meet some day, and you think this stuff is worth it, you can buy me a beer in return :-)
(C) Jens Dalsgaard Nielsen
credit for license this goes to phk@FreeBSD.ORG