Robotis OpenCM 9.04

Robotis OpenCM 9.04

Connection Type
Number of servos
Audio Support
Camera Support

The OpenCM9.04-C is the same as the OpenCM9.04-B except for the two TTL connectors (used for the AX series) has been replaced by two XL-Type TTL connectors (used for the XL-320). Both versions C and B are compatible with this firmware to connect with EZ-Builder. This controller is also used in the Robotis Bioloid Mini that can be controlled by EZ-Builder with this firmware.

Setup Video Walk-through

In this video, DJ demonstrates how to connect and control dynamixel AX-12 servos with the Open CM 9.04 in EZ-Builder using the Dynamixel plugin. There are step instructions below that define each step. The TTL servo ports of the Open CM 9.04 are UART #0 on the Dynamixel plugin. Ensure the plugin has the UART #0 selected for the TTL servo ports to work.

Setup Steps

  1. Download and install EZ-Builder
  2. Follow the instructions from Robotis to install Arduino IDE tools.
  3. Download DJ's OpenCM v1 Firmware Sourcecode (Updated April 8, 2019)
  4. Tutorial to compile and upload the firmware
  5. If using Dynamixel servos, install the Dynamixel Servo Control into EZ-Builder. Set the Dynamixel plugin to use UART #0 for the Open CM 9.04.

Controller Specs

OpenCM9.04 is an open-source controller that runs on a 32bit ARM Cortex-M3. The 3-Pin connector(XL-type) is used to control DYNAMIXEL XL-320 with TTL communicatio in EZ-Builder using the Dynamixel plugin. For AX & MX series molex connectors, the OpenCM Expansion Board is needed

Arduino IDE Configuration

The suggested IDE for programming the OpenCM9.04 is the official Arduino IDE. The tutorial link below will recommend downloading and installing the Arduino IDE. However, you will also need to install the Robotis OpenCM libraries and tools into the IDE.

The OpenCM9.04 can be programmed with the EZ-B firmware for a variety of capabilities when connected to EZ-Builder. The tutorial to program the EZ-B firmware can be found HERE. This hardware was added to EZ-Builder in this beta release and newer.


Most Arduino's connect to EZ-Builder via 9600 baud. This controller has the technical power to connect at a much higher rate. The firmware is set for 921,600 BAUD, which is very quick! When following the connection tutorial, ensure you specify the correct baud rate for this firmware.


The ports on the OpenCM perform different features based on their usage. The diagram above demonstrates how the ports are connected to EZ-Builder. The Ax ports can be either Analog Input or Digital I/O. The Ax also function as Dx ports. The UART 0, 1, & 2 are connected to UART 1, 2 & 3, respectively.

Hi, i followed the instructions and connected the opencm9.04 with AX12-A and every thing is fine but "Get & set all servo positions" is not responding in EZ- Builder. Kindly guide me/
Did you watch the video tutorial?
Yes Sir. After going through that only i have started building my project.