/Dynamixel_Serial

Arduino library to control Dynamixel servos (AX, MX and RX series) over serial.

Primary LanguageC++GNU Lesser General Public License v2.1LGPL-2.1

Dynamixel Serial library

Arduino library for interfacing with Dynamixel MX series servos over serial comm v1.0.

Usage

Notes on baud rates

  • As of Arduino 1.6.x, the exact baud rate computed by Baudrate = 2000000 / (b + 1) must be passed to this library or the Arduino serial library may choose a hardware baudrate with too large of an error for proper communication. This issue is confirmed to occur if 57600 baud is used to communicate with a Dynamixel servo setup with b = 34, which is the default for RX servos.
  • Never set the baud rate register to a value of zero. This configuration is unsupported by Dynamixel and many UARTs are not capable of reliable communication at this speed which can result in you no longer being able to communicate with the servo. Reflashing the firmware via the dynamixel to USB interface is the only known way of recovering from this state.

Connection of Dynamixel AX or MX to Arduino

You do not need a half to full duplex circuit if you do not wish to receive ANY data FROM the Dynamixel servo, as we are only setting up the Dynamixel servo we will leave this circuit out and connect directly to Arduino to make things simple.

AX/MX (Pin)            Arduino and/or Power supply (Pin)
====================================
GND (1) -------------- GND (GND)
+12V (2) -------------- +12v (VIN)
DATA(3) ---330 ohm R--- TX (Arduino Pin 1)

Connection of Dynamixel RX to Arduino

Signal conversion from TTL serial to RS485 using a MAX485 or equivalent is necessary in this case. Half duplex bidirectional communication are also supported using this interface.

A 0.1uF ceramic capacitor shoud be wired between the Vcc and ground pins of the MAX485 and placed physically near the chip.

A 120 Ohm +- 10% resistor should also be connected between the A and B data lines at the output of the MAX485 and at the end of the bus to prevent signal reflections and ensure reliable communication.

--Wiring--

Dynamixel RX (Pin)      Device
====================================
GND (1) -------------- GND
+12V (2) ------------- +12v
RS485_DATA+(3) ------  MAX485 pin 6
RS485_DATA-(4) ------  MAX485 pin 7

Additionally, the following connections must be made between the MAX485 and Arduino:

Arduino             Device
====================================
GND (GND) --------- MAX485 pin 5 (GND)
+5v --------------- MAX485 pin 8 (Vcc)
Pin 2 ------------- MAX485 pins 2 and 3 (~RE and DE)
TX (TX1 if Mega) -- MAX485 pin 4 (DI)
RX (RX1 if Mega) -- MAX485 pin 1 (RO)

The ground must be common(connected) between the Arduino and Dynamixel servo. If the Arduino is NOT powered via USB, the +12v source may be connected to the barrel jack (preferred) or the Vin pin of the Arduino in order to power the Arduino.

CAUTION: The +12v power supply must not be greater then +14.8Vdc as per the Dynamixel datasheet. Take extreme care when connecting to the Dynamixel servo as incorrect connections, especially of power, will likely cause permanent damage.

Changelog

  • 21 February 2017 - Implement and document RX series servo support as well as Arduino 1.6.x compatibility. Fix build errors in examples.
  • 25 March 2015 - Library migrated to GitHub.
  • 25 April 2013 - A few errors have been fixed in Dynamixel Library
  • 28 June 2012 - Dynamixel Library re-written from the ground up... there is no longer missed commands set to the servo.
  • 10 April 2012 - Dynamixel Library now has example of how to set-up and program a Dynamixel Servo via a Arduino
  • 17 January 2012 - Library and Arduino sketch in download section updated to work with Ardunio 1.0

More Information

Attribution

License

Released under LGPL, see LICENSE.txt