[Coco] rgb2vga

[Mathieu Chouinard]

Hi Ed,
thanks for the information.
I managed to score a few nice things on ebay:
1 MSX2+, 1 Atari 130 XE, 1 Commodore 128 and 1 Ti-99/4A
all still in the box ... hours of fun (and probably cursing too)
at the horizion ...
Mathieu

On Tue, Sep 20, 2016 at 11:19 AM, Zippster <zippster278 at gmail.com> wrote:
> Hi Mathieu,
>
> R, G, and B are taken in on pins 1,2,3 as usual, composite sync on pin 13.
>
> Here’s the routing for the board I did (Luis’s original board has the same circuit).
> <https://drive.google.com/open?id=0B1sgl615FlGnWmhISkRVZkRjU0k <https://drive.google.com/open?id=0B1sgl615FlGnWmhISkRVZkRjU0k>>
>
> As you can see, there’s no separate hsync and vsync on the connector, so for the
> C128 RGB port, you would probably want to run some patches between the RGBI and
> analog RGB connectors.  You’ll also need to patch the intensity line (with a voltage divider)
> to the FPGA IO header as detailed on Luis’s site.
>
> An easier approach is probably to have one end of your cable a 10 pin header connection
> and just use the analog port.
>
> A note of caution…  as you probably already know, the C128 will be putting out TTL level
> signals, so you’ll want a series resistor on the RGB lines (to act as dividers with the already
> present terminating resistors on the board) in order to drop the voltage to levels that won’t
> harm the FPGA IO.  Also be sure you’re running with the ground fix on the hsync divider, for the
> same reason.
>
> You may have to adjust the FPGA programming to sync the pixel clock with the one in the C128
> more closely for the intensity signal to be applied to the video conversion in a stable manner.
>
> This issue could be avoided by using some logic and a simple resistor DAC to create pseudo-analog
> signals from the TTL inputs before sampling.
>
> I hope that helps, and good luck.  :)
>
>
> - Ed
>
>
>
>> On Sep 20, 2016, at 9:17 AM, Mathieu Chouinard <chouimat at gmail.com> wrote:
>>
>> On Tue, Sep 20, 2016 at 9:48 AM, Robert Gault <robert.gault at att.net> wrote:
>>> Mathieu Chouinard wrote:
>>>>
>>>> what is the pinout of the rgbin connector?
>>>> Mathieu
>>>>
>>>
>>>
>>> 9  7  5  3  1
>>> .  .  .  .  .
>>>
>>> .  .  .  .  .
>>> 10 8  6  4  2
>>>
>>> RGB pins on Coco3
>> sorry I was talking about the DB15 RGBIN connector.
>> I'm trying to build a cable for a commodore 128
>>
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A te quaeso, sicut in Aeneidos libro quarto Aeneas, elocutus
desiderium erigendi suum obeliscum in templo Venereo Didonis, ab ea
quaesivit, tuae domi an meae?