joystick_sdl

One of the limitations of the standard ROS joy package is that it depends on the linux/joystick.h header. This sucks, especially for ROS users on Windows and OS X, who would enjoy being able to remotely teleop robots using a locally-connected game controller… without a VM.

So the idea here is to piggy-back on the cross-platform joystick support available in SDL. So far, it is tested to work with a Logitech F710 and DualShock 3 (wired) in Ubuntu Trusty 14.04 and Mac OS X 10.10.3, with the following caveats:

• For Mac OS X, the F710 must be in DirectInput mode (“D” on the top switch).
• Detecting disconnects on OS X works only with SDL 2.0.4 and above.
• Analog triggers don’t work, nor does motion control or force feedback (SDL limitations). Triggers register as ordinary binary button presses.
• No attempt is made to expose “hats” or “balls” from the SDL API.
• Unlike joy_node, which uses IO blocking, this package polls the joystick at a fixed interval (default 25 Hz). This is a consequence of building it on a game platform, where input is typically processed at a set point in the main loop.
• Unlike joy_node, there’s (currently) no way to differentiate multiple devices connected to the same computer.

Finally, SDL provides (via the GameController API, some ability to abstract joystick mappings so that disparate units can swap in for each other more easily (eg, every device has an “A” button, even if it’s the one with an X on it on a PlayStation pad). There’s some rough-in to support this here, but it’s unclear how desirable it really is going forward, as most robots have a standard joystick they ship with, and a button mapping to match. For now, this is unused, as it’s more valuable to have this package be a drop-in replacement for joy.

This package is under active development. Caveat emptor.