🚀 go-pugleaf

On 5 mrt, 12:27, "David L. Jones" <altz...@gmail.com> wrote:
> On Mar 5, 7:47 pm, Lionel <use...@imagenoir.com> wrote:
>
> > Per the subject line. I want to experiment with direct PAL video
> > generation from a microcontroller, with the minimal number of parts.
> > I'm thinking that a good starting place might be to use a CPU clock
> > that's based on the PAL subcarrier frequency (4.43MHz) multiplied with
> > a PLL+VCO+Divider to give me phase reference points, & directly
> > generate the composite colour signal via an R2R ladder.
>
> > So, some questions:
>
> > 1) Is this a reasonable concept? (I'm comfortable with per-cycle level
> > timing & coding)
>
> A few people have had (limited) success with direct composite PAL
> video generation directly from a micro, like this one:http://www.rickard.gunee.com/projects/video/pic/gamesys.php
> Ordinary quality, but shows that the minimum parts count is a PIC and
> two resistors!
> Much faster micros are available would obviously do a bit better than
> the PIC.

Note that his _PIC_ solution is BW only, he does color on a SX micro:
with an about 53MHz clock(12x Fc )
 http://www.rickard.gunee.com/projects/video/sx/gamesys.php

There are several cheap PAL modulator chips, so a PIC and
for example a MC1377 modulator chip would be 'low chip component
count'.
MC1377 is old, and uses a 4.43MHz xtal, quality is good enough for
games.

The alternative is a PIC and a sparate 8.86 MHz (2xfc) oscillator,
some 4053 switches, some 4013 FF, some inverters and xor gates to make
a PAL modulator.
I'd use the MC1377:-)
Or you need a very fast PIC !