[Coco] Generic VGA adapter

[Steve C.]

It is showing +5v after the resistor with no load (unconnected) and close
to 0v when connected to pin 16. This was the cheapest convertor on Amazon,
and now that I look at it there are a serious number of "missing" - empty
SMD pads for diodes, or resistors (I'm not sure what would have been on the
empty pads) near the SCART connector.

On Tue, Jan 24, 2017 at 6:11 PM, Barry Nelson <
barry.nelson at amobiledevice.com> wrote:

> I do suggest you measure the voltage at pin 16 with a voltmeter with
> everything connected. If it’s not between 1 and 3 volts, preferably near 2
> volts, that is your problem. I use an old cell phone charger to externally
> supply the 5 volts needed for the signal on pin 16.
>
> On Jan 24, 2017, at 12:46 AM, Barry Nelson <barry.nelson at amobiledevice.com>
> wrote:
>
> *Steve C.* towmater at gmail.com
> <coco%40maltedmedia.com?Subject=Re%3A%20%5BCoco%5D%20Generic%20VGA%20adapter&In-Reply-To=%3CCACAVgyHesogaf3AYKzUcZYg-4M-p9q%2BAN-TKbenNVJFRrN9WdQ%40mail.gmail.com%3E>
> *Mon Jan 23 01:03:29 EST 2017*
>
> I built this RGB-SCART-HDMI adapter, but it is seemingly just taking the
> composite video on pin 20 to HDMI and ignoring the RGB. Any ideas where
> this went wrong?
>
> On Jan 23, 2017, at 1:56 AM, Barry Nelson <barry.nelson at amobiledevice.com> wrote:
>
> One of 3 things is probably wrong.
>
> 1) You did not connect a +5V supply to a 100 ohm resistor to pin 16 as shown in the diagram.
>
> 2) You did not connect the ground of the 5V supply to ground on pins 4,5,9,13,17, and 18.
>
> 3) you got unlucky and got a SCART to HDMI converter that does not support RGB video. Send it back and get a different one. If this is it, let me know as it will be the first time this has happened.
>
> *Steve C.* towmater at gmail.com
> <coco%40maltedmedia.com?Subject=Re%3A%20%5BCoco%5D%20Generic%20VGA%20adapter&In-Reply-To=%3CCACAVgyGdLho06%3DfhF1NMm8XAWVoUzP2YOk7h50Ksr36paZhpGw%40mail.gmail.com%3E>
> *Mon Jan 23 23:26:32 EST 2017*
>
> I fear it may be the cheap SCART converter. I have the 100 ohm connected,
> and the grounds are all tied to the coco GND, (unless it is supposed to
> have a totally isolated 5V + ground? I used a pad conveniently marked 5V TP
> on the MB for power) I even went the extra length of using shielded coax
> for the RG and B lines with the shields tied to ground on the SCART
> connector and motherboard.
>
> Sorry to hear that. This is a picture of the one I used: https://hackaday.io/project/7366/gallery#2245eff5259883e5811b6937ed1ff55a
>
> All grounds are common. Perhaps that test point does not supply enough current. At pin 16 you should show 1 to 3 volts to ground. Pin 16 is RGB mode select To set RGB input mode, put 1 to 3 volts on this pin. (5 volts via a 100 Ohm resistor will set it at 2.1v due to the 75 Ohm load inside the SCART input device).
>
> http://martin.hinner.info/vga/scart.html
>
>
>
>