I've been researching about how LCD shutter glasses work at an electrical level and I think I've got a pretty solid conjecture on the inner workings of the Famicom 3D System.Driving the shutters
At first I thought that LCD shutters used simple 0~5V signaling, but actually they must be driven with AC of a few volts and a couple of hundred Hz, feeding DC into them would destroy the liquid crystals. This would explain the seemingly complex circuitry found inside the HVC-032 adapter.Synchronizing the shutters to the computer
Only one signal wire is used for synchronization in the HVC-032 adapter, which is Pin 11 of the expansion port, also known as OUT1. Not having done any actual measuring on a real Famicom with a 3D enabled game, I presume that the logic state of this signal selects which shutter is enabled at any point in time. If this is correct, the state of OUT1 would be low for an entire television frame, high for the next one, then again low on the next one and so on.
Now I can speculate on how the Nintendo adapter works:
- The unknown Sharp IC forms an oscillator of sorts, in conjunction with X1, a crystal oscillator (it would be nice to have the value of this crystal ). The synchronizing signal from OUT1 enters this chip, presumably to alter the output parameters of the oscillation.
- The second IC is a dual op-amp, probably used to buffer/amplify/invert the signals for driving the shutters, applying AC into only one of them while leaving the other alone, according to the state of OUT1.
By applying the generated square wave into the left shutter, an inverted version of the same square wave into the right shutter and controlling whether the normal or the inverted version of the generated wave appears at the common terminal between the shutters we can drive the LCD shutters in an alternating fashion. If the normal version is applied to the common terminal, the left shutter would not see any voltage at all (both of its terminals being at the same potential), but the right one will see a rapidly alternating voltage between its terminals (its terminals will always be in contradicting logic states because of the inverted pulses between them). When the inverted version is applied to the common terminal, the roles reverse. This might or might not be the driving scheme used in the HVC-032, but it sure is elegant.
If my hypotheses are correct, I could build my own Famicom 3D System out of my eDimensional glasses, an oscillator and a bunch of logic gates.
Looks like the link you posted is just a jpeg of the 3D system.
Damn! I got carried away by the context of where I found it and by "clues" in the file name (sh and 15 as schematic and 15 pin connector).
Post Merge: May 31, 2010, 01:06:08 AM
First tests done on a real Famicom:
Pin 11 seems to be outputting a 30 Hz (
or maybe 60 Hz
can't be 60, too slow) square wave (haven't been able to measure it but the green LED hooked up to it flickers pretty badly and apparently in sync with the doubled screen elements). I've injected that signal into the v-sync input of the VGA dongle of my eDimensional glasses and while it manages to sync up to the signal, it looks like the glasses are alternating at half of the TV frequency. Guess I'll need to build my own LCD shutter driver or at least work something out with the original VGA dongle.
seems to pulse the sync line at all times as soon as the game starts up, regardless of whether you're playing on normal or 3D mode, while 3D Hot Rally
keeps it low on normal mode and pulses it on 3D mode. Does this mean that the glasses are always working when playing Falsion with them, even in normal play?
ericj and/or UglyJoe, I presume you've played these games before. Does the weird thing about Falsion make any sense?