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View Full Version : [Question(s)] MX-28 and Arbotix



jakerockwell
07-12-2012, 09:23 AM
Hey!
Weve been experimenting with an MX-28 and an arbotix so that ultimately we can have a functioning pan tilt camera turret with position control. Everything seems connected properly using the pololu usb. the first batch of code from the google project page (https://code.google.com/p/arbotix/wiki/BioloidController) complies just fine and uploads to the board. but then, nothing. the servo is powered properly and the tx/rx pins are tied as instructed but i am not getting any movement out of the servo. are there any suggestions on where to go next? the code pages are very detailed on setting up but dont suggest there should be any issue once the code is uploaded. also, is the LED on the edge of the board a status light? its not blinking or lit. i know its hard to debug without having the controller in your hands but any suggestions would be greatly appreciated.


Thanks!
Phillip and Jake

Upgrayd
07-12-2012, 12:44 PM
Did you set the baudrate correctly? Check the Robotis support page (http://support.robotis.com/en/product/dynamixel/rx_series/mx-28.htm) for the default servo settings.

You may also run into other issues. I am not sure if the arbotix people have updated their libraries to fully support the MX control table.

tician
07-12-2012, 05:16 PM
The 'default' baud rate for the MX/RX/EX-series servos posted on their sites vary. Some say it is "1" for 1Mbps while their other sites say it is "34" for 57600bps, so YMMV.

lnxfergy
07-14-2012, 06:42 AM
You may also run into other issues. I am not sure if the arbotix people have updated their libraries to fully support the MX control table.

While the PID parameter addresses are not currently defined in the library, everything else should work as expected. I've been using MX-28/64/106 servos with our ArbotiX-ROS firmware for many months without issues.

-Fergs

lnxfergy
07-14-2012, 06:44 AM
Hey!
Weve been experimenting with an MX-28 and an arbotix so that ultimately we can have a functioning pan tilt camera turret with position control. Everything seems connected properly using the pololu usb. the first batch of code from the google project page (https://code.google.com/p/arbotix/wiki/BioloidController) complies just fine and uploads to the board. but then, nothing. the servo is powered properly and the tx/rx pins are tied as instructed but i am not getting any movement out of the servo. are there any suggestions on where to go next? the code pages are very detailed on setting up but dont suggest there should be any issue once the code is uploaded. also, is the LED on the edge of the board a status light? its not blinking or lit. i know its hard to debug without having the controller in your hands but any suggestions would be greatly appreciated.


Thanks!
Phillip and Jake

Nothing in that sketch will toggle the LED. I would suggest changing:

BioloidController bioloid = BioloidController(1000000);
To read:

BioloidController bioloid = BioloidController(56700);
As all of the MX-28s that I've received still had 57600 as their default baud rate.

-Fergs

tician
07-14-2012, 09:52 AM
As all of the MX-28s that I've received still had 57600 as their default baud rate.

-Fergs

So I'm not the only one then. Prior to a firmware upgrade, the two beta MX-28's we received would actually default to 57600 every time they lost power.

lnxfergy
07-15-2012, 08:00 AM
So I'm not the only one then. Prior to a firmware upgrade, the two beta MX-28's we received would actually default to 57600 every time they lost power.

Yup, I had the same issue with my beta MX-28s, and I'm guessing it was a heck of a bug to find, because it took them over a week after I reported it.

-Fergs