Supergun AV with Sony CXA1645

Having recently aquired a fairly cheap King Of Fighters '96 MVS cart, I've decided to finally follow my dream to build a supergun in lieu of my eventual purchase of a MV-1 or MV-1F board (anyone selling one cheap?). For now, I'd like to have the supergun output composite AV to work on my TV (although I plan on making the connection from the harness modular so I could easily add in RGB support once I get the money/space for a dedicated monitor.) Now, I have no intention of spending ~$70 on a JROK encoder, and thankfully Antipasta came to the rescue with the suggestion that the Sony CXA1645 chip from a Playstation, Saturn (even Genesis?) could be shanghaied for that purpose. Has anyone here done this, or could provide a link to any sort of walkthrough/schematic for the circuit I'd need to make?

Also, I've got a fairly non-working NES that I plan on using for the shell of the supergun, which brings the question: it would be ghetto and lo-fi as all hell, but is there any way I could tap into the NES' AV outputs for this project and just use the encoder there?

 

The CXA1645's datasheet has a recommended circuit. You can find the datasheet here: http://f5ad.free.fr/Docs_Composants/CXA1645.pdf

The NES doesn't use RGB so it doesn't have an encoder.

Only Genesis 3 have a 1645 IIRC, older Genesis/Master System/Neo Geo/Amiga have CXA1145. Also many Playstations have integrated video encoders.

 

1145 indeed in a MegaDrive. You can do it with them, yup... although (especially the earlier ones) aren't superb chips. The best ones are rare as the excrement of a rocking horse!!! Still, if you have a sacrificial Genesis or Playstation, go for it!!

If you're going to be buying a chip, though... then use a JRok instead.

 

That's the whole reason I'm looking for a CXA1645 - I don't really feel like spending $75 on what I could do on my own for 1/3 of that. I've got an old, non-working SCPH-1000 model stashed away somewhere, so I've already got the chip as well - just need to get the assorted other bits from Radioshack.

Unfortunately, I think I'm going to need an interpreter as well - those datasheets appear to have just what I need, but I can't read electronic schematics to save my life. I've done a good bit of soldering projects, but they've all been things with "...For Dummies"-esque tutorials found online.

 

Just use the application circuit on page 10.

Pin 1 goes to ground
Pins 2, 3 and 4 go to RGB In through 3 capacitors (parts list: 3 0.1uF capacitors, non polarized e.g. ceramic)
Pins 5, 8, 11 & 17 are not connected
Pin 6 is a subcarrier input - a sine wave or low voltage pulse (there are extra schematic examples in the notes, point 5)
Pin 7 goes to +5V if you're going for NTSC - it is the NTSC/PAL selector
Pin 9 is the Y signal clamp - just connect to ground via another 0.1uF cap (add to parts list)
Pin 10 is the sync input
Pin 12 is Vcc1 - the positive supply. It connects to the +5V supply. There are also two capacitors connected to ground in parallel on this line. They are a 0.01uF unpolarized, and a 47uF polarized (e.g. electrolytic). The polarized one has to go the right way round (+ to +5V)(add caps to parts list)
Pin 13 determines the internal reference current. Connect it to ground via a 47k resistor and 0.1uF polarized capacitor in parallel
Pin 14 in the internal reference voltage. Connect to ground via a 10uF polarized capacitor. The notes seem to suggest tantalum bead here.
Pin 15 *ERROR ON DIAGRAM* This is C out not Y out!!!! If you're not using S-Video, don't bother connecting anything here
Pin 16 Y out! As per 15, don't connect anything to this pin if you're not using S-Video
Pin 17 Internal filter FO adjuster. Connect to ground via a 20k 1% tolerance resistor for NTSC
Pin 19 Vcc2 - another voltage supply. Connect to +5V, and connect to ground via the same type of capacitors as for pin 12
Pin 20 Composite out. Connect via a 75 ohm resistor and a 220uF polarized capacitor
Pins 21-23 RGB out. Don't connect if you don't want RGB out
Pin 24 Connect to ground


By the way, is it a SOP in the Playstation? If so, be careful! They can be quite hard to solder/desolder sometimes!

For someone not into reading circuit diagrams, I would certainly recommend doing some reading up. The Babani range of books are great. Robert Penfold books in particular were great, I thought... and he's a nice guy! He helped me with a school project. http://www.babanibooks.com/bb7.htm I don't know if they are available in the US. Still, a browse through Amazon might be of use... look for books on schematics or circuit diagrams.

How about:

http://www.amazon.co.uk/exec/obidos...8-2/ref=sr_8_xs_ap_i2_xgl/202-3423629-8203831

http://www.amazon.co.uk/exec/obidos...8-1/ref=sr_8_xs_ap_i1_xgl/202-3423629-8203831

http://www.amazon.co.uk/exec/obidos...8-4/ref=sr_8_xs_ap_i4_xgl/202-3423629-8203831

The middle one appears to be American, and should be on Amazon US.

 

Yeah, all the stuff on the original PlayStation is surface mount. Bitch to remove without damaging if you don't have a proper toolbench setup. A standard iron and desoldering braid just doesn't cut it. Nevermind the pins are small as hell as it is. Personally I'd find paying the $70 to be cheaper and more time efficient.

-hl718

 

Not to be a smartass, but if it was that easy I don't think I would have made mention of the fact that I don't understand a thing those datasheets are saying.

I appreciate your detailed pinout, but that still has me at a loss - I'm really not good with all that electronic lingo. I suppose that would be a pretty thorough walkthrough for someone with experience, but I've got no idea what all that means. Where do I get +5v from? Where and how do I connect the capacitors? Where's the RGB in from the Jamma harness? How does this hook up to a composite video RCA jack? Etc.

I may have a look through the school library and see if they have any basic electronic primers on my day off, or even (though I'm not holding my breath) those books you mentioned.

Either way, a $75 Jrok encoder might be easier, but I'm not sure I'd consider the price to be at all 'cheap', and I'd rather try to do it myself than pay someone $75 plus shipping for something I could conceivably pull off on my own. Plus, there's bragging rights involved that way. :-D

 

Apologies, I didn't note that Pins 2, 3 and 4 are RGB IN - this has been amended.

Composite hooks up to Pin 20 - through the components mentioned above. Well, I tell a lie... a composite (phono) terminal is of course TWO pins... the outside barrel is ground.

You get +5V from your power supply.... I assume as you're making this circuit you're building a test rig, and you have a suitable PSU.

You'd want to make this on a PCB or stripboard. The components go where I mentioned above.. e.g. if a pin connects to ground through a capacitor, then its solder 1 end of the cap to the pin, and the other to the ground terminal.

Not trying to sound derogatory, but this is a simple circuit diagram. As such, it is a great way to learn to read them! You'll be able to pick up the circuit symbols from anywhere, e.g. here. Note that they miss out a resistor symbol - the one that's kinda ---/\/\/\--- is also a resistor.

I'll try and do you a little electronics 101 diagram with the schematics in a sec.

 

Hopefully this (amended) diagram clears things up.

I made some divisions to make things clearer. The red and orange sections are optional. The green and blue go to PSU and JAMMA connector respectively.

This leaves a few simple components - hopefully this makes it easier. For example, take pin 2. The pin connects to 1 end of a capacitor, and the other end of the capacitor connects to the R pin of the JAMMA connector.

The black dots you see in some places are connectors. This shows a fork in the circuit - where 2 things connect to 1 thing. I'll make some more diagrams to better explain this tomorrow - and a stripboard layout.



Parts List(for composite only)

Capacitors
0.01uF Ceramic x2
0.1uF Ceramic x4
0.1uF Tantalum Bead
47uF Tantalum Bead x2
10uF Electrolytic
220uF Electrolytic x2

Resistors
75 Ohm x2
47k
20k Metal Film 1% tolerance

Miscellaneous
Breadboard (size to follow)

That lot should set you back... what, maybe $5-10? Less if you're lucky!!! To locate the chip now, you might be looking at $40! crazy! Hurrah for old Playstations!!

I'll work on that SCIN when I'm more awake!!!

 

Wow, that's a lot more detailed than I really expected - thanks a lot! That last diagram you drew up actually makes things pretty clear - I'd almost hazard to say that I could possibly construct a circuit with that knowledge.

Oh, I know - I'm really that bad at reading circuits. I should probably take the time to learn though, especially when constructing my own supergun, no?

 

Well, to be honest, you don't really need circuit diagrams for a 'gun. Its pretty straightforward pinouts. For the RGB to NTSC circuit though, yes.

Like I said, didn't mean that to be critical of your abilities.... more that BECAUSE it is a simple circuit, it should be a good one to study and learn from.

Didn't get a chance to do the stripboard layout at work... will do that later.

 

Retro> Where is he supposed to pull the SC input from?

-hl718

 

I'm working on that, as I said! I'm thinking from a circuit using a hex inverter, such as a 7404. Pretty sure I saw another design using one of these... I'll dig it out. Needs a crystal and a few other components, of course!

*Edit*

One circuit!

You could just pinch the SC generator from there, or use the whole circuit if you wanted. He has a nice stripboard layout all prepared... git!! hehe

 

<total ignorance> And what's the SCIN for, anyways? </total ignorance>

 

Colour subcarrier... you want colour, don't you?

Here's my modified version of his diagram, to look like the above. It is NTSC, with an NTSC crystal. If anyone sees any mistakes... blame the original author! Just kidding - let me know



*EDIT* Gah, mistake number 1! The chip is a 74HCT04

Parts list

Capacitors
10pF Ceramic
33pf Ceramic x2
10nF Ceramic
100nF Ceramic

Resistors
4.7M

Oscillators
3.579545Mhz Crystal

 

Okay, so let me see if I'm following this correctly: Pin 4 on this circuit above goes to Pin 6 on the CXA1645 circuit, but that's all, right?

And what's this mysterious 14-pin chip here, anyways? Also, is this 3.579 timing crystal something that would easily be obtainable at a typical Radio Shack, or would I need to rip it out of some other NTSC device (like, say, a NES...)

Really appreciate the effort you're going to on my behalf, btw.

 

ARSE!!! I KNEW I'd left something out!!! It is a 7404 Hex Inverter, e.g. 74HCT04.

Crystals are common - that should be an NTSC crystal. Yeah you'll find one in a NES, maybe PSX, most consoles really... and yes Radio Shack should have them for like a dollar or two.

Yup, pin 4 to pin 6.

As I say, you could build his circuit... just leave out the composite stripper, as you should have sync anyway. I'll see if I can do a stripboard for the basic one tomorrow, though.

Oh, and I'd get two IC sockets if I were you, too! Better than soldering chips directly... just in case you make a mistake!

 

I made one of these last week with an AD724 from Analog Devices...free samples

They're pretty simple in terms of application circuit - I did have a dead MegaDrive2 I ripped the encoder out of but I didn't want to mess about too much with the luma/chroma delay lines so I just redid it. I've reproduced my (rather sparse...sorry!) design document below:

Pin 1 - Video standard - Tie high with 10k resistor (NTSC), low (PAL)
Pin 2 - Analog GND - Tie low
Pin 3 - Crystal input - Crystal bypassed by varcap to ground
- One end of the crystal is put into pin3, connected to one end of a variable capacitor (I used a 0-22pF type). The other end of the varcap and the other end of the crystal both go to your ground.

Pin 4 - Analog 5V - Tie high
Pin 5 - On/off - Tie high with 10k resistor
- you can add a switch here to save power if you want - pull pin 5 low to disable the chip.

Pin 6 - Red in - Input, 75R to ground, 0.1uF cap coupled
Pin 7 - Green in - Input, 75R to ground, 0.1uF cap coupled
Pin 8 - Blue in - Input, 75R to ground, 0.1uF cap coupled
- These three are identical: red/green/blue inputs come in from your JAMMA connector to one end of a 0.1uF unpolarised capacitor, then the other end of the cap goes to the relevant pin. You can add the 75 Ohm resistors (between the input and ground) if you want; they're not strictly necessary but I used them.

Pin 9 - Chroma out - 220uF cap coupled, then 75R to output
Pin 10 - Composite - 220uF cap coupled, then 75R to output
Pin 11 - Luma out - 220uF cap coupled, then 75R to output
- Exactly the same as in retro's excellent diagram. Don't forget to attach the ground lead on the socket to circuit ground!

Pin 12 - Mode select - tie low (FSC operation)
- This chip can run in a couple of modes. With pin12 pulled low you need a 3.579545MHz crystal for NTSC and 4.433619MHz for PAL. Use a parallel-resonant type with a shunt capacitance of around 18pF. Also don't forget that if you make it PAL then your TV/monitor must support PAL60 or it won't work with the majority of arcade boards!

Pin 13 - Digital GND - Tie low
Pin 14 - Digital 5V - Tie high

Pin 15 - VSYNC - Tie high with 10k resistor
Pin 16 - HSYNC - Composite sync
- Just run a wire straight from composite sync on the JAMMA connector to pin16. If you have separate HSYNC and VSYNC available then use both pins, if you only have composite sync then you need to tie pin 15 high and input it to pin16.

Putting a nice big capacitor (I used a spare 220uF one) across the 5V/0V connections is also sensible.

Put that lot together and it should all work! Hopefully that'll help somebody...total parts cost was probably about £5 so it's a pretty cheap option

Stone

 

Just noticed your addition to this thread - thanks a lot for the added info!

The project's been on hiatus for a while, as finding a cheap MV-1 or MV-1F board to go WITH my Supergun has proven rather difficult. Plus, I haven't had a chance to get back to my parents' place and see if I still have that old PSX I can pull the CXA from. And with school starting, and still working a part time job - well, free time has been at a premium, let me tell you.

I wonder if my bosses would mind me soldering things at the front desk of a hotel...

 

I ordered one (yay for free samples indeed) but I've realized that the chip is incredibly small...like 10 millimeters long. Can you mount that on anything? Or did you even bother? I'd like to do this as neatly as possible (for me, anyway).

Edit: Sorry, I'm electronically inexperienced...and well...would like to understand your directions better.

Edit Again: Ok, I think I understand things a little bit better, but don't you need some kind of variable resister (called a potentiometer, right?) to tweak the R, G, and B signals? Or are those what the 75ohm Resisters are for on the RGB inputs and the Chroma, Composite and Luma outputs for? Or am I just missing something?