3 May
2009
3 May
'09
12:10 p.m.
Mike,
You say you understand the principle behind the MC3418 so we will fast
forward past that point. If the output of the device ( data out ) toggles
between one and zero and back ( one sample period each ) then your display
needs to increase up and down by what ever the integration voltage will do
in that time period. To make it simple, let's just say that on your display
you will increment or decrement the vertical component ( Y ) by one. If the
output stays high ( or low ) for four consecutive sample periods, then you
need to increment ( or decrement respectively ) by how much the integrated
voltage will transition at the new slope setting ( the new gain on the
integrator ). For giggles lets say that the delta increase is now four
instead of one. Just increment ( decrement ) by four instead of one. If you
play around with this it really is easier than it sounds. If you aren't that
concerned with an accurate portrayal of the data but a representative
waveform is good enough, just always increment / decrement with the same
number and all you will lose is the amplitude accuracy. Hope this helps.
Best regards, Steven
----- Original Message -----
From: "Michael B. Brutman" <mbbrutman-cctalk at brutman.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Sunday, May 03, 2009 7:08 AM
Subject: MC3418 CVSD Encoding (Was: Re: Looking for IBM PS/2 or PCjr
SpeechAdapter Tech Ref
Michael B. Brutman wrote:
The PCjr Speech Adapter sidecar is rumored to be identical to the PS/2
version, at least as far as the BIOS support on the adapter goes.
Ok - it looks like nobody has ready access to a tech ref for the PCjr
version or the PS/2 version of the speech adapter. I am sure its buried
in a nice binder with a slipcover somewhere but I don't have the PS/2
set - I only have the PC family set of docs and they didn't make one of
these for the PC or XT.
The part of the adapter I'm interested in is driven by a MC3418. This
chip does CVSD encoding and decoding of waveforms. I understand the
principle behind CVSD encoding and decoding, but not enough to start
writing code. I want to write some code takes CVSD encoded data and
displays the waveform on a screen, for a sound editor. Does anybody
have any experience reading MC3418 encoded data?
Thanks,
Mike