frunobulax

Cool! I've been wanting one for a while too!

I can give you all the block diagram, and the schematic (still have to draw up the final one as it stands now) and someone with a little soldering skill could put another together. You may even come up with a better solution on how to put it on a board. I don't think the type of perfboard I used was intended to have this many IC's jammed on it... There is literally NO WHERE else I could put another chip without cutting some traces. I'm toying with the idea of working on a PCB for it. That would make it a fairly straightforward 'kit' to assemble at home.

Why not just go with this version? Well, primarily my reasons were: 1. Didn't know of that version (or even this forum) before I started this project. 2. When I set out on designing it I wanted to do something using parts that were around cheaply at the time the 7800 was new. 3. I happened to have a ton of logic IC's laying around and wanted to put them to use. 4. I was looking for a 'bigger' (read: longer lasting) project. If I went with a microcontroller, it would have been finished that same day and I would have had to find something else to do. (That'd be like pulling out a 30 piece jigsaw puzzle when I was really looking for a 3000 piece-r.) To each their own though. Of course! Here are some pictures of the dual port install: Everything unplugs from the controller board so it can be removed, replaced, upgraded, or worked on. The NES jacks from Parrallax (which come molded with little ears) slide down into clips I made out of left over plastic from cutting out the holes. So they can be removed easily, but are solid enough to not move when inserting or removing a controller plug. I put both jacks on one side of the 7800 so that one could plug in an NES advantage to both ports without an extension, or having to split the advantage's cord to reach to both sides. This is the underside of the board when I had it out to fix a misswired chip I found today when testing the second controller:

Just got finished building the board and installing the first of 2 NES ports in my 7800. It's already set up to work 2 NES controllers but I only have one NES jack hooked up right now because I got tired of soldering and wanted to play some games! The mess of cables going to the NES jack from the board is temporary (hence it's sloppiness) until I make the right breakout cable to handle both NES ports, but it works for testing one at a time. This version includes it's own clock generator so no need to borrow the clock from the system anymore. It also now uses both A and B as 2600 "fire" buttons (instead of just 'B' like perviously) as well as work both the right and left button respectively in 7800 mode. I'll go into detail about it all when it's done, but I'm thinking I'll take that to the hardware forum rather than this thread.

PAL versions don't. Thanks for the correction. I should have started that sentence with the phrase: "I'm new to the 7800", and ended it with: "...that I'm aware of". It's still not an issue for this project even if one doesn't have access to the system clock somewhere else. A separate clock generator is actually more ideal for many reasons. One, is that it allows the controller adapter to remain completely external to the 7800, requiring no internal connections at all unless one wants to have "Start" and "Select" function. It'd function like the micro-controller based one the person above made, just constructed with 74-series logic chips instead.

Unfortunately, this setup won't work for most of us because not all 7800s have the expansion port so it will be much more difficult, if not impossible, to pull the required clock signal. Fortunately the circuit can be run off it's own clock. Taking it from the board is not necessary. It's just easier and cheaper than using a separate oscillator. The external version I'm planning on making will incorporate it's own clock generator. The whole thing seems to run best at around 500KHz - 1MHz as it stands right now. I've even run it off a clock signal I could easily audibly hear through a speaker (meaning it was less than 20KHz) without a noticeable loss in performance. That all being said, there is nothing stopping anyone from tapping a wire off thier motherboard even if the expansion port is installed on your system. The fact may be that there might even be a better place for me to grab the 7800's clock. As I mentioned, the current circuit isn't fast enough to run at full 7800 speed. The signal has to be divided first anyway. Perhaps there is somewhere on the board I could grab an already divided clock. I haven't looked into it that much. But simply having an expansion port installed isn't going to stop you from making this mod in any one of it's forms I'm contemplating. EDIT: Oh I see... you were saying you -don't- have the external expansion port! The 7800 in the picture doesn't have one either. I've never personally seen one that had the external port installed actaully. However, all 7800 motherboards have the connections for the port on the actual board. This is what I used. I Soldered my new clock line for this circuit to the actual 7800 motherboard where the expansion port would have gone had it been an expansion port model. All 7800's have these internal taps regardless of whether or not they have the external port.

New version. This one isn't rigged up out of left-overs this time. Half as many chips used as a result. I also added a NES controller jack. The version on the breadboard has only one controller port because I ran out of space to fit the 2nd controllers register chip on. This chip will fit on, and be added to, the final circuit board. The whole thing will easily fit inside the 7800 shell and provide 2 NES controller compatible ports that will be hooked up in parallel with the external 7800 ports, so I can still use them too. It's really nice to have the working SELECT and RESET right there on the NES controller and the overall control is very sharp: Way sharper than any Atari-type controller I currently own.

I would say Pole Position II (if anyone plays it) also requires it. Although you can probably get away with breaking by downshifting, I find that the extra button as the break peddle makes it much easier to avoid collisions.

If the emulator does it too its a software problem. A common cause of "writing junk" would happen when a 6502 memory pointer becomes corrupted. This could be due to a variety of reasons. I'm starting to wonder what kind of reasons... I don't know near enough about the 7800 processor to begin to think of any myself. Are people saying that the 'half width' thing also happens in the emulator? Perhaps there is a certain rom version that interacts with a certain hardware version and this was the hardware version that was emulated thus showing the glitch? Does that make *any* sense? lol! I don't know near enough about this particular hardware to even guess at this point. I'm starting to think that its a certain revision of 7800 hardware that causes this. You would think other games would be affected in some way if there was something wrong with the machine and again, my choplifter works just fine on other 7800's. Its not completely crazy. According to the FAQ, Food Fight will lock up on certain revisions of the 7800. I don't think anyone really knows for sure. I've heard talk of timing issues but again, you'd think other games would be affected but none apparently are. Very strange. With my luck, I probably have a combination of hardware glitch with the 7800 (bars) and software glitch with my version of choplifter (half-witch). Typical... Hahaha!

I wonder the exact scheme too. I know that the Proline stick is compatible with the 2600 (and 2600 games run on the 7800) because it ties the "Button" (aka fire) pin to ground with either controller button press. However, at the same time it's doing that... it connects the pins on the controller port that would be used for analog paddle inputs on the 2600, to Vcc or +5v in this case. I found this out while debugging the NES controller adapter I am currently working on for 7800. It is major reason I decided to not make both "b" and "a" buttons on the NES controller equal a "fire" in 2600 mode. It would require another gate or some more components from what I know now, as connecting both buttons to the 2600 "fire" pin also allows current to flow between the 2 buttons when in 7800 mode. Effectively making the 7800 think you are pushing both at once no matter which you pushed. I was able to exclude one button from this fiasco with a diode, but adding a diode to the other line caused the button not to work properly in some 7800 games. I think I need to just understand what is going on a little better. Any help is greatly appreciated.

If the emulator does it too its a software problem. A common cause of "writing junk" would happen when a 6502 memory pointer becomes corrupted. This could be due to a variety of reasons. I'm starting to wonder what kind of reasons... I don't know near enough about the 7800 processor to begin to think of any myself. Are people saying that the 'half width' thing also happens in the emulator? Perhaps there is a certain rom version that interacts with a certain hardware version and this was the hardware version that was emulated thus showing the glitch? Does that make *any* sense? lol! I don't know near enough about this particular hardware to even guess at this point.

Do you happen to have a second system to try your copy on or do you happen to have a second copy of choplifter to see if this happens? Not yet > Here is a photo of my label. BTW: the system has No expansion port, and no indication of a cut out on the shell. I removed the RF modulator and added a composite video mod (which is what is used to make the pictures I posted), but it did the same thing through the normal RF.

Nice! My amp is on a little board that is wrapped up in electrical tape that sits where the RF adapter used to be. Getting that RF adapter out was a bitch. not only are the solider points massive, but the entire housing acts as a giant heat sink. It's not fixed to the board in any way, so I thought I would protect it from making any unwanted connections bouncing around in there. I'm planning on using the space above the 2 chips you described for installing the NES controller adapter board I am working on. I haven't yet worked out where to put the jacks though. Kudos to whoever came up with using the RF-unit's pin header with an internal PC CD-rom audio cable. Makes for a super clean install. Love all the usable space in these units!

I don't know if it's real clear in my pictures I posted, but if you notice, the black bars at the top go away after the half width glitch begins.

Mine also does the same thing with the bars. After a while of playing (or some times right away) the graphics will glitch out where everything is only half as wide as it should be, and the colors of the sprites go all weird. That's the second image.. I forgot to turn the flash off when I took it though.