Comment: That SCART cable thread you linked to is very long and has many different designs, If you keep on reading, including a lot of input from myself. I would not make/have never made one exactly like the schematic on the first page, though it is pretty close.
There are many ways to roll your own SCART cable, and even more different TVs to use them on. They all require a blanking signal to pin 16. The specs say 1v-3v is required for RGB switching. Some TVs require exactly 1-3v, some are less fussy. Sometimes TVs work with 5v, direct to pin 16, some TVs work by just bridging sync (pin 20) to pin 16 with a bit of wire. Sometimes TVs require both blanking (1-3v to pin 16) and AV/AUX/4:3 mode switching signals (12v to pin 8 ), although you can usually select AV/AUX mode manually or with a remote too (auto-switching via 12v to pin 8 can also obviously be useful for cabs where you want the TV to be in AV/AUX/4:3 mode automatically when turned on).
In the absence of a "valid" blanking signal/voltage, SCART input TVs should revert to composite video (pin 20 only), which we don't like here
SCART Specs:
http://pinouts.ru/Home/Scart_pinout.shtmlThat you say you detect 5v after the 100ohm resistor makes me think that your TV either doesn't have 75 ohm termination on pin 16, or that it expects 1-3v to be online before it gets to pin 16 and is 75 ohm terminated. Conveniently, either way, the solution is the same.
A couple of things for you to try:- after your 100 ohm resistor, attach one end of a 75 ohm resistor to your 5v going into pin 16, and the other end to ground. Like a T, with the resistor as base --> ground. If all you have is 100ohm resistors, they should work too. This will lower the voltage levels to ~2.1v (or 2.5v with 100ohms), either way within the 1-3v range required.
Test the above first, I'm pretty sure it'll work by itself. Then:
- I suggest attaching 1k ohm resistor inline onto composite sync signal, whether you get it from enabling composite sync in VMMaker (make sure to generate & install the modes as well) or twisting H&V or whatever. With termination, this should give you 0-0.3vp-p composite sync to spec. If this makes you lose your sync again, try a lower value resistor like 300-680ohm.
- If you've enabled composite sync properly in VMMaker, you might even disconnect V-Sync (VGA pin 14) to remove potential signal noise as all the composite sync info is carried on the H-sync (VGA pin 13) anyway (However, I'd probably leave V-sync connected anyway unless it causes a problem, as then your cable is then more useful for other purposes).
BTW - You can setup VMMaker so that you get both PAL and NTSC band video modes, you just need to get your monitor presets right (#tip requires multiple crt_range#'s). But that is for another post/topic.
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Topic: New to GroovyMame - will my Hardware work?? (Read 2970 times)
