[Coco] Is MM/1 to SCART practical?

[Barry Nelson]

I had problems producing a composite sync with the proper wave form shape inexpensively which is why I steal it from the composite video port. Besides, the SCART video standard actually expects a full composite video signal on that pin, although it  will work in RGB mode if you just supply a valid composite sync. Also, the MM/1 probably has a different video out circuit. I have no idea if it's signal parameters fall close enough to SCART 480i video to make this work. The CoCo 3's RGB output just happens to have the same peak to peak voltages, timings, and everything that happen to coincidently match what SCART expects for a 480i RGB signal which is why this works. Really the CoCo 3 effectively outputs an SCART standard signal, it is just not wired to an SCART plug. That is why this works. I do not know if that is the case for the MM/1, you will need to research that. SCART can accept either a 50Hz (PAL) or 60Hz (NTSC) vertical sync rate at either 15khz horizontal or 30khz horizontal sync. It expects the signals on the RGB lines and the composite sync to be .7 volts peak to peak, and the sync must be a negative going sync pulse.

On Aug 21, 2015, at 7:19 PM, coco-request at maltedmedia.com wrote:

> Date: Fri, 21 Aug 2015 16:02:12 -0500
> From: David Ladd <davidwladd at gmail.com>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Subject: Re: [Coco] CoCo 3 RGB to SCART to HDMI update
> Message-ID:
> 	<CAHW2jkC3YsmPOYgOtpPYzH48s22BnkzTuGaakVvDH79Lh113qg at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
> 
> I wonder if this would be a good option to try on my MM/1.
> 
> I have tried the RGB2VGA project on my MM/1 and sadly it doesn't work as I
> had hoped.
> 
> Thanks for the write up on this.  Will give me a direction to try with my
> MM/1.  Though sadly I wont have the composite video source though.  I
> wonder what is the best solution for producing a composite sync out of the
> H and V sync lines.
> 
> +----------+
> |David Ladd|
> +----------+