[visionegg] Re: Hardware for Vision Egg

Hello gentle persons,

On miércoles, novi 5, 2003, at 13:02 Europe/Madrid, Christophe Pallier wrote:

a while ago the german computer magazine offered a nice and cheap USB I/O project (total cost are around 60 €). Copies of the article (sorry, only german), the PCB and the main I/O chip are available via

http://www.emedia.de/@119D6xh6hRI6/bin/ hw.pl?Aktion=P&Proj_Nr=0308_1&SID=

you need some additional, more "regular" things like resistors etc. which are listed in the article. If I remember right there is even a small "first-step"-software listening in the article (I'll check language and platform). The project allows to develop several I/O project for on the USB port -> Detection of a "key pressed", LED control, you name it. If there is interest I will mail the magazine and ask wether they allow that the article gets translated and published within visionegg in english.

The latencies (the time delay) giving for the USB port in the previous mail are measured as what? From my experience with PCB design USB latency for "low speed" devices like keyboards range between 75 and 300 ns (nanosec) - this seems to be valid for almost all usb 1.1 and 2.0 controller chips. The detection intervall mentioned seems to me like a software (keyboard input detection) and not a USB signal problem. It seems to reflect the time intervall this software use to read out the input buffer?

cheers,

Markus




Also, I did some preliminary tests with portaudio (a cross-platform realtime sound API) as a trigger output, and it had 20-100 msec latency on Windows XP with motherboard audio. This is worse than parallel port performance, so I gave up. However, there is low-latency audio hardware available (e.g. using ASIO drivers by Steinberg) which might make a huge difference. Also, it is possible that Mac OS X systems would have better latency through the audio path.

Maybe it not reasonable to expect too much from motherboard audio, I do not know...
Anyway, I fear that one will always have to test and calibrate the timing for each audioboard (and driver).

For linux and MacOS X, Jackit may be an interesting project to try and get low latency audio (as ASIO under Windows)

See http://jackit.sourceforge.net/docs/faq.php

But it is not compatible with Windows...


As an aside, it is somewhat worrying that parallel ports will no longer be around at some point in the future.

Quite worrying indeed.

Yet, I found a company that sells USB response boxes (cf. http://192.131.102.99/rurb/tech.html) and, if I understood correctly an email they sent me, there would be a systematic (i.e. constant) 20millisecond delay between the key press and the registration by the USB system. If true, this would be not too bad for many situations, even if there are cases where this may not be sufficient.


Christophe Pallier
www.pallier.org

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