4 Apr
2024
4 Apr
'24
7:35 p.m.
On Apr 4, 2024, at 3:12 PM, Brent Hilpert via cctalk
<cctalk(a)classiccmp.org> wrote:
That is similar to what the CDC 6612 controller for the DD60 console display does. So
given that you're sending the resulting step waveform through a deflection circuit
with finite bandwidth, you do in fact end up with a continuous vector with rounded
features. How nicely rounded depends on the bandwidth and the number and size of the
steps. For example, the DD60 display doesn't look all that elegant, but it is
definitely well rounded, simply because the step clock is 10 MHz and the deflection chain
bandwidth isn't a whole lot more than that. So the fact that you're dealing with
what originally was a step waveform with just 7 positions for X and Y isn't at all
obvious in the final image.
paul
On 2024Apr 4,, at 7:22 AM, Adrian Godwin via
cctalk <cctalk(a)classiccmp.org> wrote:
This 'scope clock also uses circle generators rather than vectors to
produce well-formed characters. It mentions a Teensy controller so I don't
think it's the original made in this way - the first I heard of was too
long ago for that. But I don't know if it's an update or a separate design.
https://scopeclock.com/
<https://scopeclock.com/>
Technically, the scopeClock is generating neither
curves nor vectors, it's generating pixels in an XY display - it's just that
they’re of fine enough resolution and fast enough that they’re seen as a smooth-enough
curve on the CRT.
The MIT/Electronics-magazine and Wyle techniques are using analog electronics to generate
portions of sine waves for selected phase periods and phase relation such that when
applied to the XY cartesian display you get continuous portions (chords) of circles. Some
digital logic gates the analog sine generators appropriately to produce the chords and
line segments, with offsets, in a sequence to form characters.
The scopeClock, in contrast, is using DACs in the microcontroller to generate (discrete
approximations of) sine wave segments - which is to say it’s relying on the abilities of
inexpensive current-day high-speed digital electronics.