Infinity Foodpedal External for Pd

Infinity footpedal external for Pd

Last updated: August 24th, 2009

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About

The VEC Electronics Corporation make a nice sturdy USB footcontroller, traditionally used by transcriptionists to reverse/play/pause/forward audio. These pedals generally retail for $50-60USD and are easily found through online shops. When I found the Infinity IN-USB-1 (local link) for $4.99 at the local Goodwill, I instantly thought it could be repurposed as a nice foot/stomp controller for Pd.

I purchased it, brought it home, searched around for ways to read it, experimented and failed to use HCS's HID and then decided to just write my own abstraction. I hate reinventing the wheel, but when the other wheels don't fit it's sometimes a necessity.

Download

The following archive(s) are available for download:

infinity-footpedal-1.0.tgz - Released August 24th, 2009. Includes the source code for the external, help patch, and test application.
10-infinity-pedal.rules - Udev rule file to create /dev/infinity-footpedal symlink and set the permissions to 0664 with group 'plugdev'. Copy this to /etc/udev/rules.d/ and restart udev.

Images

Since this is a software project, there really isn't much to show. The following are images of the pedal itself, the help patch, and a short demo video.

Description

Features:

No polling, pure multithreaded event driven I/O - it's gentle on your multi-gigaherz cpu. ;)
More than once Pd object instance per physical device. Sometimes it's just convenient to have more than one instance rather than dispatching from a single source. Well, this external supports that. A single thread will dispatch to all Pd [infinity-pedal] instances.

How to build:

Extract the tarball: tar -xvzf infinity-pedal-1.0.tgz
cd to the directory: cd infinity-pedal-1.0
if your m_pd.h isn't in /usr/local/include, edit the Makefile and correct the INCLUDES line.
invoke make: make
If all goes well you'll have a infinity_pedal.pd_linux sitting there.
Copy infinity_pedal.pd_linux and the help patch infinity_pedal.pd_linux to somewhere in your pd external path.
Like sudo cp infinity_pedal.pd_linux infinity_pedal.pd_linux /usr/local/lib/pd/external/

Note: I've discovered that libc < 2.9 may complain about pipe2(). If so, edit infinity_pedal.c and change:
pipe2(pfd, O_NONBLOCK);
to:
pipe(pfd);
or better still, give me a patch that solves this at build-time. :)

Troubleshooting

If you have difficulty, first make sure the device shows up in lsusb:

Bus 001 Device 005: ID 05f3:00ff PI Engineering, Inc.

If it does, at least the pedal is recognized. You can then try the readpedal program (included) to troubleshoot. Make sure your permissions are correct and that you can read the device. If readpedal works but Pd can't find it, make sure that your Pd path is correct and the binary external has been installed.

How does it work?

The quick and dirty explanation (or the code speaks for itself):

The first instance of [infinity_pedal] causes a thread to be started. This thread performs blocking reads on the device, specified as the first creation argument. Subsequent instances of the [infinity_pedal] are simply registered in the list of objects to be dispatched. When pedal data is available from the reading thread, it sends outputs to the outlets of each of the registered Pd objects. Only those outlets whose state has changed will have data sent to them. A mutex is used in order to protect the list of registered Pd objects from changing while the pedal state is being dispatched. When the final Pd object instance has been deleted, the reading thread is sent a message (via pipe) to terminate.

Like all software projects, this one has its shortcomings:

Linux only. Likely to work on OSX, please let me know what you find out!
Does not currently support more than one pedal at a time. This would be a little bit of work, but I don't have more than one pedal to try it with anyway. If you send me one I'll make it work. :)
Changing the device at runtime is not possible. This is probably a bogus use case anyway, unless your udev is doing something odd an you're replugging the pedal a lot. Most users can just use the udev rule and hard-code the path.

And credit/mention is required for the following resources/links:

http://code.google.com/p/footpedal/ - Python project used to read the pedal. The code here borrows heavily from that project. I wouldn't have known how to read the pedal otherwise -- so thanks!!
http://www.jinvoke.com/USB-hardware-access-from-Java I didn't really peek at the source, and there are a lot of Winshit screenshots, but maybe if you're doing something creative with the pedal from Java (Processing anyone?), it might be a useful resource.

If you'd like to contribute to this project and make it more better, please contact me!