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Product: USB2AX

What is the USB2AX?

The USB2AX is a small interface to control Dynamixel servomotors like the AX-12 from a computer. It plugs into a USB port and has a 3-pin Dynamixel connector to be connected to the servos.

If you're in a hurry, jump to Quickstart !

dynamixel_parts_top.jpg

Status LED: the LED lights up GREEN when the USB2AX is ready, RED if not (no driver, USB authentication error…).
The pads and jumper under the PCB are detailed in the GPIO and SPI page.


What is it useful for then?

The USB2AX is a direct way to control servos to move legs, arms or claws in a robot with an embedded computer (laptop or Raspberry PI for example).
You can also use it as a tool to setup, diagnose or fix your servos.
Have a look at some examples of application!

What servos can it talk to?

The USB2AX can talk with the Dynamixel servos which use a half-duplex TTL interface (3-pins connector).
More specifically:

  • All of the AX servos (AX-12/AX-12+/AX-12A, AX-12W, AX-18F/AX-18A).
  • The “T” versions of the MX servos (MX-28T, MX-64T, MX-106T).

Features

What are the limitations?

Fortunately, the USB2AX can not do everything ;-)

  • The USB2AX can not communicate with the Dynamixel servos using the RS485 interface (the one with 4 pins).
  • Neither can it control any sort of hobby/RC servos or other brand of robot servos.
  • Compared to the USB2Dynamixel, it also lacks the RS232 port (with its big DB9 connector) used to program some controllers from Robotis like the CM-510.
  • It can not supply power to the servos (see Q: How to power the servos).
  • It is not a generic USB to Serial (even though it can be modified to be one) and has very different capabilities than the LN-101.
  • The USB2AX reserves the ID 0xFD, so it cannot be used by a servo on the bus.
  • It does not make coffee, but could be used to create a robot that does!

Quickstart

Read the Quickstart Guide, and be on your way :-)

To go further...

Miscellaneous

History

usb2ax_family_named.jpg First prototypes, v1.0, v3.0a, v3.0b, USB2AX Mini, v3.1a.
v2 never saw the light of day, it was very similar to v1 and scraped when I realized it was going to be much bigger than v1. Instead, I went on with v3 that used smaller components (0402 passives instead of 0603, QFN instead of QFP for the ATmega). And finally the commercial v3.1a, which differs from the original v3.1a only by its corners: they were rounded, they are now square for manufacturing reasons.

Examples of projects using USB2AX

Xachikoma by Xevel, the four-legged reason for creating the USB2AX. 4 legs, 5DOF each, plus powered wheels instead of feet.
Charlotte by KevinO, an hexapod controlled with a Raspberry Pi through an USB2AX.
HexaWheels by Siempre Aprendiendo, an hexapod with wheels and a Raspberry Pi.
Grinder by Nick Donaldson of http://gotrobots.com, a big hexapod using MX-28T and one USB2AX, and with free wheels to move like the Roller-Walker!

USB2AX on the web

Xevelabs, Xevel's blog.
Fourwalledcubicle, Dean Camera's blog.
PoBot (FR), a review by the French robotics association PoBot.
Seeedstudio, the manufacturer of the USB2AX v3.0a.

Acknowledgments

Contributors:
Nicolas Saugnier (Xevel) - Idea, original schematics, firmware, and everything else starting at v3.0.
Julien Le Guen (JLG) - Eagle schematics and routing of first versions.
Richard Ibbotson (iBot) - optimization of the code for lower latency, improvements to the schematics, implementation of advanced functionalities.

Thanks:
Dean Camera for making the greatest USB library for AVR, LUFA.
Weston T. Schmidt for making the cross-platform app DFU-Programmer!
Trossen Robotics, Robosavvy, SeeedStudio and Adafruit for the help (direct or indirect) to bring the USB2AX to market.

Inspirations:
Arbotix RoboController
Arduino Uno
Adafruit ATmega32u4 Breakout Board
Ruggeduino, for over-voltage protection on DATA

Download / files

product/usb2ax/usb2ax.1365710594.txt.gz · Last modified: 2013/04/11 22:03 by xevel