Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!voder!pyramid!nsc!icldata!altnet!altos86!dtynan From: trejo@nprdc.arpa (Leonard J. Trejo) Newsgroups: comp.unix Subject: Request for Real-time HW/SW Info Summary: Looking for advice on real-time micro hardware/software. Keywords: real-time microcomputer hardware software operating systems Message-ID: <939@altos86.UUCP> Date: 30 Mar 89 02:41:57 GMT Sender: dtynan@altos86.UUCP Reply-To: gatech!ucsd!nprdc.arpa!trejo (Leonard J. Trejo) Organization: Navy Personnel R & D Center Lines: 81 Approved: dtynan@zorba.Tynan.COM We're planning to buy a microcomputer for conducting psychophysiological experiments. We now use a Masscomp 5500 running RTU 4.0 ("real-time" UNIX) to control presentation of graphics stimuli and to digitize and store physiological signals. Problem is that RTU's time is not "real" enough for some of the things we want to do. For example, we want to flash a visual stimulus on a graphics monitor for exactly one video field at 125 ms after the onset of data acquisition on an A/D converter and then record the response latency of a subject (button-press) to the picture with an accuracy of 1 ms. Everything must be synchronized to within 1 ms, e.g. |------------S---------------R---------------------| | | | | Time 0 125 X 1000 (ms) Start Stimulus Response End A/D Onset Time A/D Transfer Time Transfer S should be 125 +/- 1ms and X should be measured to within +/- 1ms. On the Masscomp we time S by putting a light sensor on the face of the graphics CRT which sends a pulse into one channel of the A/D converter. Although it's a bit awkward, this can provide stimulus timing accuracy limited only by A/D sampling rate, which can go up to 1 MHz/# channels. We can time X similarly. However, this only works well for simple events, such as the whole screen turning on or off. It wouldn't work for the appearance of a character on the screen whose coordinates vary from trial to trial. Besides, we want to get rid of the screen sensor and use a mouse for subject responses. Our thinking now is to acquire a dedicated PC (e.g. an 80386 based AT clone) to produce stimuli and measure responses. The system should be able to do the following: o Be able to send a 16-bit parallel word out which marks the onset time of a visual (graphic) stimulus (one per video field) with a latency of 1 ms or less. This to be followed within 100 ms by two words which code the type of stimulus and its screen coordinates. o Be able to respond to a mouse button press and send a parallel word out in 1 ms or less which marks the time a mouse button is pressed (this is probably asking too much). This to be followed within 100 ms by two more words which code which buttons were pressed and mouse coordinates when pressed. o Graphics capability of minimum 640 by 480 pixels with independently addressable color lookup tables using 8-bit ( or higher) D/A converters (i.e. 16.7 M color palette). Also capable of simple animation (e.g. video game quality). Library of C graphics subroutines. Sound-producing chip would be a plus. o C compiler. (UNIX development system would be a plus, but is not required.) o Cost of hardware and O/S to be about $5K. Most of this boils down to very tight coordination between graphics and parallel digital I/O plus fast intterrupt responses. We'll use this PC as a fancy stimulator which sends/receives event-related synchronizing digital signals to the Masscomp. These signals will be monitored by a fast parallel I/O board controlled by the Masscomp data acquistion/control processor, which will coordinate the digital and analog I/O. Thus, the Masscomp will serve as a fancy A/D converter and near-real-time signal processor. Sorry to be so long-winded, but if you have suggestions please send them to my by e-mail. If there's interest, I'll post a summary. Thanks in advance. L. J. T. ============================================================================ ARPANET : trejo@nprdc.arpa UUCP: ucsd!nprdc!trejo Phone: (619) 553-7981 Postal Address: Leonard J. Trejo, Ph. D. (AV) 553-7981 NPRDC Code 52 San Diego, CA 92152-6800