[Coco] Re: [Color Computer] Re: Adapter from Coo3 to SVGA

[Mark Marlette]

Most of these chips sets when in their final product form has OSD, on
screen display. This is a micro that controls what Roy is doing in his
setup program and more.

Atmel's AVRs are VERY reasonably priced, many $2-5 in small qty. They
have flash, EE, and ram. Perfect fit for this.

We are using the AVR and a MAXII CPLD for the PS/2 keyboard and mouse
interface for the SuperBoard. Inside of the MAX contains all of the
PS/2 registers for the keyboard, mouse and the keyboard matrix that
replaces the out of product RCA and Mitel analog switch matrix.
Interrupt driven, programmable keys, do what ever you would like.
Matrix mode for backwards compatibility and PS/2 mode that allows
NitrOS-9 just to process PS/2 key codes and mouse coordinates. WAY too
much fun!!!

Would love to add this to the Superboard but when is done, done????

There is SO much I/O coming out of the CoCo already on the SB. What
would another 10 pin VGA connector hurt....???? :)

Mark



Quoting Torsten Dittel <Torsten at Dittel.info>:

> >    The cable connecting the coco3 to the converter is terminated
> > with a six pin DIN plug on the converter end of cable.   This plug
> > is inserted into a six pin DIN socket which is the input of the
> converter.
> > All the RGB signals available on the bottom of the coco3 are
> > connected via 10 position IDC socket to the ribbon cable
> > but the line for the #10 pin which is the PIA input is not
> connected
> > to the DIN plug on the other end.
>
> Now I see. I thought theres a (very) short piece of ribbon cable
> directly coming out of your adaptor.
>
> > Well, as far as the AL250 is concerned, the default
> > horizontal
> > position of the image is wrong leaving it off center too far
> > to the right.
> >     The AL875 has a register containing the
> > number used to divide the reference clock in order to
> > generate an output signal which is line locked using
> > a PLL to the incoming horizontal sync from the coco3.
> > The default value of this register is wrong for the coco3
> > and leaves a garbled display.
>
> Hmmm. Hadn't thought in th AL875.
>
> > Believe me, if there was a way to avoid the need to
> > program the video chips I would have used it.     When
> > I started this project, I had hoped the default values
> > would suffice but that wasn't the case.  I don't know
> > what video standard the default values conform to
> > (if any) but they don't fit the requirements of the coco3
> > video signals.
>
> That's odd. And I don't know enough about hardware to say that a
> cheap
> PAL or GAL with kind of a shift register containing the code sequence
> to
>   programm the devices would serve.
>
> Bad enough that the AverLogic chips aren't saving the register
> settings
> without permanent current. What the heck have the designers thought
> when
> they made it like this? They should keep the settings (forever) and
> only
> on a special reset signal return to any preset values. One should
> revise
> the specs of the AL chips to see what video signal timing they are
> expecting and compare that to what's coming out of the CoCo.
>
> However, if you manage to use the "RGB detection" pin, the best
> solution
> would be to add the init code to the BASIC ROMs (there was a
> discussion
> recently where there's space in the ROMs to add things. E.g. I could
> live without the picture of the Microware guys... ;-))))
>
> Torsten
>
>
>
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