Path: utzoo!attcan!uunet!husc6!mailrus!ncar!noao!asuvax!fbog!dbk
From: dbk@fbog.UUCP (Dave B. Kinzer @ Price Rd. GEG)
Newsgroups: comp.sys.amiga.tech
Subject: Analog Joysticks
Summary: Guru needed, inquire within
Keywords: Analog Joystick full range
Message-ID: <1396@fbog.UUCP>
Date: 9 Nov 88 16:48:27 GMT
Reply-To: dbk@fbog.UUCP (Dave B. Kinzer @ Price Rd. GEG)
Followup-To: comp.sys.amiga.tech
Distribution: na
Organization: Motorola Microcomputer Division, Tempe, Az.
Lines: 32


[]

  OK, I have a working VBlank driver and a working Analog joystick
adapter.  Now for a few more questions.

  The joystick resistance must be greater than the 490K specified in
the RKM Hardware manual in order to reach maximum counts.  This has been
confirmed by others in email to me.  Does anyone else have any discussion 
to add on this?

  The adapter has rock solid repeatability until the resistance gets near
it's maximum, and the returned counts get above about $f0 (easily simulated
by unplugging the joystick entirely).  The the received values start
becoming unstable and occasionally (5% of readings) jump to the far end
of the scale (readings of 2 and 5 are typical).  Since there is a (somewhat)
large capacitor on the input wire (in the Amiga), I cannot believe that there
is noise on the wire itself.  This leaves a possible problem with the paula
chip internally, like noise on the "other" comparitor input (for the small
deviations), and possibly a failure to properly discharge the capacitor
(for the large jumps).  The jumps could also be explained by a large
spike on the internal comparitor input, or a faulty latch triggering
mechanism.  Is there any discussion on this?

   It would be nice to have repeatable readings from one end of the scale
to the other.


-- 
|     // You've heard of CATS and DOGS, I'm from GOATS, Dave Kinzer         |
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