NES hardware debugging board
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Author:  Bananmos [ Sat Feb 24, 2018 10:53 am ]
Post subject:  NES hardware debugging board

I recently purchased a cheap USB logic analyser (which I have yet to try out) for getting a bit more of a debugging tool for Everdrive/Powerpak experiments. But I quickly realised that trying to connect the probes to the NES cartridge edge would not be a fun task.

So with the kind guidance of Paul@infiniteneslives, I've spent some late evenings of my vacation designing a simple pass-through PCB that would allow easy-and-obvious access to all the signals on the cartridge edge.
nesdebugboard.png [ 52.37 KiB | Viewed 290 times ]

The idea is that after soldering on a 72-pin connector and some break away IDC pins and putting on a bunch of jumpers on those, the board can be used in these ways:
1) Pass-through mode for debugging signals. Plug in any cartridge, and you can easily put on a debugging probe on any signal, by connecting it to either the top of the jumper, or to the pin (would slightly depend on which way you've chosen to have your jumpers, they could be either on the top or the bottom of the PCB)

2) Cartridge prototyping mode. Get two IDC34 ribbon cables and attach the board to a (wired or soldered) prototyping board. Would allow creating a new prototype board design from scratch without designing a new PCB for it.

3) Pimp an existing mapper design. If you have a new mapper in mind that is a slight variation on an existing one, then rather than designing it from scratch it *might* be possible (depending on what modifications you intend to do) to prototype this by plugging an existing cartridge into this debug board, and selectively removing jumpers from the IDC-pins, connecting them to a smaller prototyping board.

I plan to have the board manufactured by "itead studio", as recommended by Paul. The minimal order should give me at least 10pcs of them, which gives me one or two for personal use and a few to pass around. If a lot of people are interested then I might do multiple orders - but only after I've confirmed the first one works without problems. Although if a lot of people in the US want one, then we might save on customs if someone just clones my order and orders PCBs/components to distribute to others.

For the first run I'll go with 1.2mm board thickness, as that plays nicely with toploaders (even though I don't have one myself) and is still usable on a front-loader if you have a Game Genie at hand. But I am also considering ordering a 1.6mm version to make the Game Genie redundant.

The Designspark PCB file, a slightly modified version of Paul's NES component library (just adds a 72-pin IDC connector) and the Gerber files can be found here if you want to have a closer look around.

The design is close to done but not 100% final yet. So any feedback/suggestions for improvments is welcome. And also do let me know if you're really keen on having one to play with soon, and you might be able to have one from the first order... :)

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