Samstag, 28. Juli 2012

Gyro calibration experiments with a turntable

Last weekend, I've dug out an old turntable to see how well the gyroscope of the Move can be calibrated with the USB-based calibration blob. The turntable has the advantage that it has a known rotation speed (two modes: 33 RPM and 45 RPM), so this can be used to see if the values we get back from one of the gyro axes somehow relates to real-world values.

Before I tried the turntable method, I just played around with the raw Gyro values to see what I can get out of them. I wrote a very simple QGraphicsView-based GUI to see the output visually, and this is what came out of that example:

As you see, that was not really anything to write home about, so next up was the turntable experiment. With that, I could scale the raw gyro readings so that "1.0" (in my case) corresponds to e.g. 45 RPM. Coupling that with an audio player using Qt MultimediaKit, one can translate the turntable movements into playback rate values and control the media player just as if it were a vinyl record:

In this week, I've been working on perfecting the calibration algorithm, cleaning up the API for the calibration part of the library and hooking everything up to Sebastian Madgwick's AHRS algorithm and visualizing the result with Qt3D.

Mittwoch, 18. Juli 2012

hidapi on Linux: Now supporting hidraw enumeration

As I've been posting about previously, I've been working on a hidapi patch to get device enumeration working correctly for Bluetooth HID devices on Linux. After about two months, and thanks to the great support and feedback of Alan Ott (the hidapi maintainer), the patch landed in mainstream hidapi yesterday.

How does this benefit the MoveOnPC project? It now allows us to use the PS Move Motion Controller under Linux via Bluetooth and without having to resort to source-code-level hacks. For most users, this will just be a transparent improvement.

In other news, I've been working with Benjamin yesterday on getting his OpenCV code working on Linux, and while it worked, the LED writing did cause a noticeable pause every 4 seconds. Fixing this by using my experimental "multithreading" branch did help, but we had to increase the delay for the initial calibration blinking. I hope to look into possibilities to improve this for Bluetooth devices on Linux, so that we get the same write performance as on OS X and Windows.