[Coco] again: CoCo RGB to VGA conversion

[mmarlett at isd.net]

james,

Since I did the research and it is common knowledge that most, not all,
monitors start their hsync freq ~31 khz and up today.

I looked at various solutions and have come to the same conclusion as
Torsten. More than what the CoCo really needs. A lower cost solution could
be produced. Again this is just prelim leg work all looks great on paper.
My design will be in a CPLD with external support circuitry.I will not
start another design until the SuperBoard and Ethernet is completed.

Mark
Cloud-9


>Mark
>
>One major problem is that most modern monitors now will not do 15 KHz 
>horizontal sync any more. I did come across a LCD monitor that did.
>
>The AL 875 chip is the more promising of the lot. My only concern is that
an 
>8 bit ADC has only about 50  dB signal to noise ratio. While there
literally 16 
>milion colors, not all will look well. In reality many of the darker
colors and 
>hues will not be accurate due to potential noise issues. Secondary issues 
>are that the input signal must stay within the range of the ADC. Thespeed
of 
>the ADC is  not a m ajor issue today as there are plenty of good quality 
>ADC that  have sufficient speed for video. 
>
>james
>
>On 17 Aug 2004 at 21:23, Mark Marlette wrote:
>
>Date sent:      	Tue, 17 Aug 2004 21:23:18 -0500
>To:             	CoCoList for Color Computer Enthusiasts 
><coco at maltedmedia.com>
>From:           	Mark Marlette <mmarlett at isd.net>
>Subject:        	Re: [Coco] again: CoCo RGB to VGA conversion
>Send reply to:  	CoCoList for Color Computer Enthusiasts 
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>> At 8/18/2004 04:11 AM +0200, you wrote:
>> 
>> Torsten,
>> 
>> I have done research on this project and it is in queue. SuperBoard
>> will be finished before this is ever started though.
>> 
>> Mark
>> Cloud-9
>> 
>> 
>> >I'm still thinking about that task. This is for all you hardware guys
>> >out there: Do you think it's possible to build a hardware for CoCo
>> >RGB to VGA conversion out of these components:
>> >
>> >For 3-channel analog RGB -> digital RGB888 ADC:
>> >
>> >http://www.averlogic.com/password/AL875_Data_Sheets.PDF
>> >
>> >For digital RGB565 -> analog VGA conversion:
>> >
>> >http://www.averlogic.com/password/AL250_251_Data_Sheets.PDF
>> >
>> >Here's a design example:
>> >
>> >http://www.2k1.co.uk/products/averlogic/www1/AL250/AL875_250.pdf
>> >
>> >taken from this site which has more info:
>> >
>> >http://www.2k1.co.uk/products/averlogic/www1/AL250/
>> >
>> >Any comments welcomed.
>> >
>> >Torsten
>> >
>> >
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>> 
>> 
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