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libdynamixel

libdynamixel is a C++ interface to the dynamixel actuators. Currently, we have library code and an utility that uses it for a few tasks like changing the IDs, the baudrate and reading angles.

The work is in progress, the documentation too, please be clement.

Documentation

The full documentation is here: http://www.resibots.eu/libdynamixel/

Compilation and installation

The build system for this library is Waf. Don't run away yet. It has the big advantage of requiring no more than Python installed on your computer. If you run a GNU/Linux OS or Mac OS, you should already have it. Here is how we compile and install it:

1. configuration
   run ./waf configure and add --prefix PATH/TO/INSTALL if you want to install it to a specific location
2. compilation
   is as easy as ./waf
3. installation
   is simply done with ./waf install, with the required rights (might need sudo if you install globally)
4. setup the proper authorisation
   please ensure that you have the proper rights to access the serial interfaces. On GNU/Linux, you might have to add your user to the dialout group and log out.

udev rule for USB2AX adapter

If you want your USB2AX serial interface to appear in /dev as usb2axN (where N is a kernel-attributed integer), you can install the udev rule. It is as simple as moving the usb2ax.rules file in this repository to the folder for the udev rules. For ubuntu, it is /etc/udev/rules.d.

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Troubleshooting read time

If the reading time seems too long, check the value of the USB latency timer. On ubuntu this value is retrieved with this command cat /sys/bus/usb-serial/devices/ttyUSB0/latency_timer. It is the time, in milliseconds, for which the device driver buffers data before making it available.

You can change this timer with the command echo 4 | sudo tee /sys/bus/usb-serial/devices/ttyUSB0/latency_timer which sets it to 4 ms for the device /dev/ttyUSB0.

Using Libdynamixel on Mac

Libdynamixel works fine on OSX, but OSX does not support the 1Mb mode (the fastest speed is 115200 bauds).

In addition, be careful that two TTYs are created when you use a USB adapter (e.g., libdynamixel): something like /dev/tty.usbserial-AI03QF2R and something like /dev/cu.usbserial-AI03QF2R. You NEED to use /dev/cu.usbserial-* and NOT tty.usbserial-* (this is because tty.usbserial is designed for modems and requires an DND signal -- that we do not send).

Using the utility

Since we are right now writing a brand new utility, the user interface is not settled yet and some commands are not implemented. You can still play with the binary dynamixel2 (the name will change) with the --help [command] option to learn how to use it.

Caution: the get-speed command gives you the reference speed used in the control loop (if any) and not the current rotational speed of the actuator.

Projects using this library

Internal projects

• omnigrasper_bo_recovery
• dynamixel_control_hw

Other projects

We would be pleased to hear from you if you use this library in one of your projects.