viletim wrote:
This looks smart.
Pin 8 is a switching signal, not a power supply. The SCART standard says the load on this line is 10k. Almost every official console SCART cable will supply 12V to this pin with some kind DC-DC converter (either charge pump or boost converter). When only 5V is connected to this pin the TV may not switch or it may force the TV into widescreen mode. To avoid this some people will cut the wire to pin 8. Others connect this pin to the input of the voltage regulator to get the 12V so the TV will switch properly. If you use this pin as power you can expect anything from 5 to 13V (unregulated), noise from an dc-dc converter gone into current limiting, or the pin disconnected entirely.
For the best compatibility I recommend you ignore pin 8 entirely and rely on external power.
Yeah, I know this. According to standard I shouldn't drain power from pin 8 but it's very convenient not to have external power supply and there aren't a lot of official cables now. Next version will have integrated DC jack on PCB (now it's floating cable which goes to board through SCART connector, not very handy but at least some compatibility). Another nice use-case with power over pin 8 is daisy chaining with only one external power supply. So simply it supports external power only on first switch link in daisy chain, and not relying on pin 8 or power from pin 8 from unofficial cables and IMO it's best compromise, user will decide what's best for him.
Also I would like to mention, that switch is almost transparent in terms of power consumption. If not lm1881 (which consumes up to 10mA), it consumes around 1mA. But I agree that having lm1881 on board is a good idea.
viletim wrote:
-For production volumes you can buy connectors directly from the connector factory. The prices are much lower than distributors and they can make them in any colour you like.
It's definitely nice suggestion, however I still need to figure out a demand for such a switch. I have no idea how many units I will be able to sell at all, and it's a bit risky to invest bigger amount of money for SCART sockets without knowing whether I will sell them all.
viletim wrote:
-Was it intentional to leave the solder mask off the vias? It would look much better with them covered (to make them almost disappear entirely use tiny 0.3mm holes).
No, it wasn't intentional, that's how smart-prototyping.com did them first time. I would like them to be covered as well.
viletim wrote:
-The PCB is long and may bend slightly if force is applied to the centre connector. Underneath there are SMT glass diodes mounted under the board between each SCART connector. If there is significant flex in the board you should rotate these diodes 90 degrees so the flex does not cause them to crack (long term failure).
On every screw I am using nylon spacer (
http://www.pololu.com/product/1982), it may not be clearly visible on photo because of nuts but such construction is sturdy enough I think. (there are 16 such spacers between PCB and bottom panel)
viletim wrote:
-It's a good idea to have both the mini-DIN8 and SCART connectors for output. Making special cables is no fun.
Yeah, but with MiniDIN I still need to solder the other end myself (being it SCART or another MiniDIN). I think I will use same straight SCART for output and by default I will provide SCART->SCART cable (which is standard, I will just need to find inexpensive source of them)
And as an option I will offer SCART->MiniDIN. BTW: where can I buy MiniDIN cable assembly like the one you're using in your NESRGB kit?
(digikey has this one:
http://www.digikey.com/product-detail/e ... ND/2625275, but I think it's too thick and expensive also)