From: Dave (dfisher_at_pophost.com)
Date: 2002-03-14 20:51:38
On Thu, 14 Mar 2002 19:33:54 -0000, sleeper75se wrote:
>Hi all,
>
>thanks for your comments, and especiall Jim for going ahead and
>testing!
>
>Allow me to suggest some more tests:
>
>What happens if you let the receiver run X-windows and you start
>dragging windows around, as well as changing virtual screens?
>Anything that is heavy on non-preemptible kernel resources is
>good...er, I mean bad. :-)
I have *11* open xterm windows (6 with continous update activity due to
streaming output) right now and 1 GUI (slickedit). I can drag the xterm
windows around and there is no loss in data. I'll try some of your remedies
below to see if I can eliminate the hit I experience with disk accesses.
Dave.
>
>Anyway, here are a couple of remedies you can try:
>
>Increasing the priority of the serial port IRQ on Linux
>http://cae.best.vwh.net/irqtune/
>
>Patching the Linux kernel (v2.4.x) so that its latency is reduced.
>You have three patches to choose from:
>http://www.linuxdj.com/audio/lad/resourceslatency.php3#L4
>
>Windows users are left with the IRQ priority tweak:
>
>Create this key in the registry (and the PriorityControl folder if it
>is not present), and reboot:
>HKEY_LOCAL_MACHINE\System\CurrentControlSet\control\PriorityControl
>IRQ#priority=dword:00000001
>
>Replace the #-sign with the number of your serial port IRQ (probably
>2 or 3)
>
>For a more detailed description look here: (you need to scroll down a
>bit - to the "REAL TIME PRIORITY" heading.
>http://members.aol.com/axcel216/newtip21.htm
>
>> What happened to that great TOSLINK idea? with a totally
>> different type of IO the loss of character problem might be
>> completely different.
>
>Yep, expect no losses. However, you are limited to two channels per
>sound card. I'm not sure there's an easy hardware-only solution to
>multiple (surround sound) channels or even if it is supported.
>
>However, I expect the only other things you you might need for
>biofeedback except EEG, is temperature, respiration, heartrate and
>ESR/GSR. Those need very little in the way of transmission speed and
>can be transmitted with 9600bps on a serial port. You could probably
>use the sideband channel in the spdif-interface as well, but I'd need
>to sign an NDA and be approved as a developer by Creative Labs (or
>Yamaha, another major sound-chip manufacturer) to take advantage of
>that. And I'm not sure I qualify.
>
>Anyway, I'm working on the layout now, for Jim Meissner to build and
>test. (Others are welcome too)
>
>> Ditto for USB - I would strongly suspect that a USB serial port
>> is not subject to the same problems as the legacy serial port.
>
>I'm afraid that is not true. According to an engineer at
>http://www.ftdichip.com (USB-chip maker) you can expect 120ms,
>(perhaps more) latencies, worst case. The only solution is to add a
>big buffer (perhaps 4kb) to the receiver hardware. I estimate a USB
>receiver with FTDI's USB chip, an Atmel AVR 8535 and 8k of SRAM will
>cost around $20-$30)
>
>Tuning the USB IRQ priority probably works too, though I suspect your
>system would be severely bogged down if you have high-speed devices
>connected. They would probably make the USB-interface request
>interrupts every millisecond. :-)
>
>Regards,
>
>Andreas
>
>
>
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:41 BST