[Coco] SCART to HDMI project.

[Doug Fraser]

Yes, by using 4 NOR gates should produce an XNOR circuit to combine the h-sync and v-sync signals off the RGB connector.  That would be a 7402 TTL chip. I'll try that because, I  think getting a 74266 XNOR chip will be hard to find where I live. 
Doug Fraser 


Sent from my Samsung Galaxy smartphone.
-------- Original message --------From: CoCo Demus <retrocanada76 at gmail.com> Date: 2017-06-13  14:08  (GMT-08:00) To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> Subject: Re: [Coco] SCART to HDMI project. 
Try a NOR, it should work

On Tue, Jun 13, 2017 at 1:41 PM, Dave Philipsen <dave at davebiz.com> wrote:

> 74266 XNOR is not a very common chip.   I'm sure I don't have one in my
> parts bin.  But you can do the same logic with a couple of 7400s (which is
> probably *the* most common TTL chip).
>
> Dave
>
> > On Jun 13, 2017, at 1:43 PM, Salvador Garcia via Coco <
> coco at maltedmedia.com> wrote:
> >
> > I had never heard of an XNOR gate, I had to look it up! 74266 :-)
> Salvador
> >
> >
> >
> >      From: Doug Fraser <frase072 at telus.net>
> > To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> > Sent: Tuesday, June 13, 2017 1:18 PM
> > Subject: Re: [Coco] SCART to HDMI project.
> >
> > I was just thinking that. I might have a xnor chip in my collection.
> Good to know about pin 10. Thanks for that. Will investigate and post my
> findings.
> > Doug Fraser
> >
> >
> > Sent from my Samsung Galaxy smartphone.
> > -------- Original message --------From: CoCo Demus <
> retrocanada76 at gmail.com> Date: 2017-06-13  11:03  (GMT-08:00) To:
> CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> Subject:
> Re: [Coco] SCART to HDMI project.
> > Also should be a XNOR gate, because the signals are inverted on coco3.
> >
> > On Tue, Jun 13, 2017 at 11:03 AM, CoCo Demus <retrocanada76 at gmail.com>
> > wrote:
> >
> >> Yes, you need to add a XOR TTL combining h-sync and v-sync and you can
> >> disconnect the pin-10 and use it on the RGB connector. the pin-10 is
> used
> >> only for the cm-8 for a strange detection system, all this undocumented.
> >>
> >>> On Tue, Jun 13, 2017 at 10:33 AM, Doug Fraser <frase072 at telus.net>
> wrote:
> >>>
> >>> That's possible. A good question is where should we get the h-sync and
> >>> v-sync signals from? The project suggests the centre pin from the
> composite
> >>> video to pin 20 on the scart connector (sync in). Is there a way to
> combine
> >>> the rgb sync signals to replace the composite sync signal?
> >>> Doug Fraser
> >>>
> >>>
> >>> Sent from my Samsung Galaxy smartphone.
> >>> -------- Original message --------From: CoCo Demus <
> >>> retrocanada76 at gmail.com> Date: 2017-06-13  07:14  (GMT-08:00) To:
> >>> CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Subject:
> >>> Re: [Coco] SCART to HDMI project.
> >>> For what you are describing: black and white, black stripes looks to me
> >>> you
> >>> connected coco3 composite video into a scart luma input.
> >>>
> >>> On Mon, Jun 12, 2017 at 11:36 PM, Barry Nelson <
> >>> barry.nelson at amobiledevice.com> wrote:
> >>>
> >>>>> frase072 frase072 at telus.net  <mailto:coco%40maltedmedia.com
> >>>> ?Subject=Re%3A%20%5BCoco%5D%20SCART%20to%20HDMI%20project.&
> >>> In-Reply-To=%
> >>>> 3Ctqar0lch5fyvl7tt6iq19drr.1497324709423%40email.android.com%3E>
> >>>>> Mon Jun 12 23:31:49 EDT 2017
> >>>>>
> >>>>> Just picked up an SCART to HDMI converter to replace my aging CM-8
> >>>> monitor. After following Barry Nelsons project on hackaday.io I have
> >>> had
> >>>> partial success with a video image. Partial in that I have a black and
> >>>> white screen and colors are grey scaled and artifacted with vertical
> >>> black
> >>>> lines. I'm not sure what is going on with the signal.  Does anyone
> that
> >>> has
> >>>> done this project have any insights as to how to make this work?
> >>>>> Doug Fraser.
> >>>> Can you post a picture of the screen? Make sure you connected all the
> >>>> ground wires and that you have 5 volts applied to the 100 ohm
> resistor.
> >>>> Double check all your wiring and measure the voltage on pin 16. Maybe
> >>> you
> >>>> got a bad converter, post a photo of the wiring also please, I may be
> >>> able
> >>>> to help more after I see the pictures.
> >>>>
> >>>> --
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> >>>>
> >>>
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> >>
> >>
> >
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