OpenCM 9.04 by Robotis
Firmware
- DJs OpenCM 9.04 Firmware (Cracked Egg) Version 4 (updated 2020-05-28)
The OpenCM9.04-C is the same as the OpenCM9.04-B except that the two TTL connectors (used for the AX series) have been replaced by two XL-Type TTL connectors (used for the XL-320).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 ARC. This controller is also used in the Robotis Bioloid Mini that can be controlled by ARC with these firmware.
Controller Specs
OpenCM9.04 is an open-source controller that runs on a 32bit ARM Cortex-M3. The 3-Pin connector(XL-type) controls DYNAMIXEL XL-320 with TTL communication in ARC using the Dynamixel plugin. For AX & MX series Molex connectors, the OpenCM Expansion Board is needed
Robotis Dynamixel Robot Skill
The chances are that you're using this OpenCM 9.04 board with Robotis dynamixel servos. If that is the case, the Robotis Open CM9.04 controller can support servos connected directly to itself or through the expansion board. Using only the controller, UART #0 is used in ARC. If using the expansion board, UART #2 is used in ARC.
I suspect the expansion board doesn't use the digital pin in the code to control the direction of the uart. If you open the open cm arduino firmware that we created, there's some comments about the undocumented pin that controls the direction of the uart. Switches between tx and rx. If that pin isn't being connected to the expansion board, it won't work. If you can find documentation on how that expansion board works, then the code can be modified for it.
What is the reason for not using the open cm directly with the ax12 servos? (Removing the expansion board from the picture)
PS, you will notice robotis makes great servos, but they severely lack documentation and modular implementation. Getting stuff to work with their controllers is mostly luck.
Bummer on the complexity and yes...Robotis has been a challenging platform for both those reasons. Five or six years ago you had to trouble shoot all of the demo code, etc. But I have still enjoyed them. Meanwhile, I am using the Expansion board because I assumed that is the only way for me to connect to the OpenCM9 board - as it has no AX12A pins.
The good news is that my IoTiny is on the way. I may also splurge for my birthday and get JD and the smaller rover. I am turning 60 after all. LOL. :-)
Hi DJ,
Hope all is well. My PincherArm with Dynamixel (from Trossen) is working now with the Open CM thanks to all of your help. I have been working with the Auto Position control and had a couple of questions. I have reviewed the manual and the tutorials. First - the servo at the base of the arm that rotates the arm left and right does not move with the controls I have tried (Horizontal, Vertical and Auto.). It is connected and getting enough power - and you can ping it. All of the other joints work. Do you think that it could be the weight of the arm - maybe a torque strength issue? The servo does lie flat, but I wouldn't think that was a problem. (These are AX12As). It works with the other controllers and software so I think that the build is correct.
My other question is the speed of the servos. I set the Action speed as slow as it can go and testing each frame it is slower - but when I save and exit and then use the execute button it is very fast - which throws the weight of the arm forward.
All in all though...it is pretty cool so far....I am building a small robot to play with the IoTiny.
One more question - is there a way to set the movement limits on servos for the Auto Position Control?
Thanks again for your help. Vicki