Article View: comp.os.msdos.programmer
Article #450Timing Problem
From: Joseph Yan
Date: Thu, 23 Jul 1992 13:33
Date: Thu, 23 Jul 1992 13:33
29 lines
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1912 bytes
Hi folks! I'd like to solicit any help I can about this timing problem: I'm working on some data acquisition from a "black box" that outputs reports of a device's position and orientation. Unfortunately, this box will output a report at a frequency between 20 reports/sec to 50 reports/sec and the time interval between reports varies depending on the time taken to process info within the "black box" and whether or not there are any invalid reports in between. My problem is that I want to be able to analyze this data for velocities and accelerations so if the time interval between reports varies, I'd like to store the time of the report along with the report itself. The time should be accurate to at least 10 ms but the clock() function in C and the other time functions I've looked at are only accurate to 55 ms (because it's updated 18.2 ticks/sec). I tried some assembler code using function call 2Ch which is supposed to report the time to hundredths of a second but I found that it also was only updated at 18.2 ticks/sec. In one technical reference I flipped through, I read that the MC146818A Real Time Clock generates a timer tick 1024 times/sec and this would be great but I haven't figured out how to access it. I'm using a 386 and accessing the "black box" through the RS-232 port but that's probably not important. Is there any kind soul out there, who can help this poor soul by telling me how, or if it's even possible, to access a timer which is accurate to 10 ms? Please reply directly to jyan@dretor.dciem.dnd.ca if you have the answer. Joe
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Path: arc1-ca.pugleaf.net!sparky!uunet!utcsri!torn!utzoo!dciem!jyan From: jyan@dciem.dciem.dnd.ca (Joseph Yan) Newsgroups: comp.os.msdos.programmer Subject: Timing Problem Message-ID: <6111@dciem.dciem.dnd.ca> Date: 23 Jul 92 13:33:24 GMT Organization: Defence and Civil Institute of Environmental Medicine Lines: 29