Subject:
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sonar.c for the handyboard
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 27 Jul 1998 21:22:24 GMT
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Original-From:
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Mark Wallace <(wallace@)IHateSpam(theory.phys.vt.edu)>
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Viewed:
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1233 times
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Hello,
I have a handyboard and 6500 series poloroid ultrasonic ranging
system. I have downloaded the sonar.c programs used to drive the
transducer for distance measurements. There appears to be a problem, or
atleast I think there is, with it. The sonar device is supposed to give
distances of up to 35ft but the TCNC time register is 16 bit and in the
program it says "if ((peekwork(0x100e)-start_time) < 0)" too much time has
elapsed and it returns -1. Therefore as soon as about 32700 counts goes
by, that value will go negative. I believe hex goes from 0 to 32768 then
-32768 to -1. In this case the difference will be < 0 if the object
is greater then about 9 ft. I have taken this out of the program and can
get accurate measurements up to atleast 30 ft but I have to look at the
value given and add multiples of 2^16 to it to figure out where it is.
Taking this out of the program also can get you stuck if you really are
out of range.
I have looked on the motorola web pages to see about this clock
and it says that the clock goes till it reachs $ffff and then flags
somewhere that there is an overflow and then starts over. I don't know
how to find out were in the chip this information might be stored. I know
the TCNT time register is at 0x100e from the notes on Simplified Sonar for
the Handy Board but I don't know where that overflow flag is stored. I
thought that maybe by setting this flag and using it in the loop you might
be about to get a greater distance out of you measurement.
Another question I have is about IC. I would like to display
numbers greater then 32000 and right now there are several int type
variables and normal C comands don't seem to work to make a "long" or any
other type that are larger then 32000. How does IC handle larger numbers?
I am only a student and don't have much experience with this stuff
so I would appreciate any feedback I can get on either of these problems.
Thanks.
Mark Wallace
e-mail mawalla3@vt.edu
wallace@astro.phys.vt.edu
Web page http://sps1.phys.vt.edu/~mwallace/index.html
"What a waste it would be after 4 billion tortuous years of evolution if
the dominant organism contrived its own self-destruction"
Carl Sagan
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