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PostPosted: Tue Feb 06, 2018 12:24 pm 
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A friend and I were brainstorming some ideas for building a version of the INL/Kazoo that would simply plug into the console like a regular cartridge, the USB interface simply a port on top or wherever it would fit. The issue of course would be the need for a custom PCB to actually construct the device.

From what I understand, the SD2SNES can do something akin to this through its USB port and custom firmware, but the SD2SNES is prohibitively expensive if all you want is a simple devcart.

Has anyone attempted a solution like this, and if so, what are some things to consider in the design?


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PostPosted: Tue Feb 06, 2018 2:49 pm 
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My very first NES cartridge project was effectively this idea.

I wasn't nearly as experienced with figuring out how to make designs low cost at the time. I was also suckered into the 'throwing high powered expensive hardware at it is fun'. The goal was to be low cost, but in the end with assembly costs it would have had to sell for closer to $100. That was the point where I realized cost could be kept much lower if USB hardware was off the board, and came up with my current product line up.

But my skills have much improved since then, and there's more and more hardware options available every year especially in terms of low cost USB. Most of my board designs over the past year have included foot print on the board to add USB functionality again, but dropping the footprint on the board is the easy part. I haven't been able to make time to complete the hard part of firmware and software to make it do anything. So still very much on my todo list.

Prior to getting USB back on a low cost board, I've been working on a new inlretro/kazzo design for most of 2017. A number of distractions in the later half of the year slowed my progress. But I'm pushing to release it by the end of this month. Having that complete takes care of large amount of the work for USB interface and host application. I should be able to port most of it over to a low cost USB capable mcu on the cartridge. That would effectively put the inlretro/kazzo hardware on the cart which is what I gather you're wanting. I'm no where close to final design, but I'm confident I can get it close to the $50-60 range in a polished retail product with enclosure and all. One pie in the sky idea I had for it was to integrate it into the action53 contributor's cartridge. The hope being it would help motivate people to submit an entry and effectively get rewarded with 'free' development hardware. IDK when I'll have things well enough together to make that happen though, I certainly can't promise it for the vol4 cart. Perhaps it could make it to vol5 though..

Anyway, I'm just trying to say I'm working on something along these lines, but can't estimate when considering all the projects I'm working on. But by all means I would support your development efforts if you were looking to take a project like this on for yourself. All the software and firmware for my updated inlretro/kazzo release will be open source, so if you utilize a similar mcu (STM32) it might help make short work for you.

EDIT: I just realized you're talking about SNES, my reply above was assuming you were talking NES.. To be honest I did really think there was a desire for much of SNES development hardware beyond what's already available. But SNES is continually gaining more homebrew interest. For some reason I've really been itching to get into SNES development myself, but I think that's primarily due to me wanting to better understand the hardware. So know that I realize you're talking SNES, I'll say that it's entirely possible for me to apply my NES plans of a USB dev cart to SNES. It's probably safe to say I'll tackle NES first though.

Byuu has made some requests for me to make a 21FX SNES bootloader device available for purchase as a dev tool. I may target a cartridge pass through version instead of exp port device though due to complications of aquiring/manufacturing a SNES EXP port female connector. If I can make that project a reality, it would effectively make the pass through device USB capable. With that you could simply plug one of my standard SNES flash boards into the pass through device and gain the features you're after.

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PostPosted: Sun Feb 18, 2018 5:52 am 
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jowijo wrote:
From what I understand, the SD2SNES can do something akin to this through its USB port and custom firmware, but the SD2SNES is prohibitively expensive if all you want is a simple devcart.


FWIW, the Super Everdrive also has a USB function. Looks like you'd have to solder on a USB port yourself though (as well as cut a hole in the cart shell) because I can't find anywhere that sells it with the USB port preinstalled. But it's less than half the cost of the Sd2snes.

https://krikzz.com/store/home/13-super- ... ve-v2.html

This would take the fun out of making something yourself though.


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PostPosted: Sun Feb 18, 2018 9:13 am 
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Would it be anything like the Extreme Flash Advance EFA-Linker, a Game Boy Advance flash cartridge with a USB port at the top for programming? (The early versions had a proprietary connector; later versions had standard mini-B.)


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PostPosted: Sun Feb 18, 2018 11:36 am 
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infiniteneslives wrote:
Byuu has made some requests for me to make a 21FX SNES bootloader device available for purchase as a dev tool. I may target a cartridge pass through version instead of exp port device though due to complications of aquiring/manufacturing a SNES EXP port female connector. If I can make that project a reality, it would effectively make the pass through device USB capable. With that you could simply plug one of my standard SNES flash boards into the pass through device and gain the features you're after.


The 21FX was the prior version of the MSU-1 that lived on the B-Bus instead of A-Bus right? If you were going to use the cartridge port instead of the expansion port why not implement MSU-1 which has more developed software than 21FX ever had? Either way though it'd be really cool to see either finally available as a standalone device. I always thought it'd be neat to see it combined with a small RAM cartridge.


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PostPosted: Sun Feb 18, 2018 12:10 pm 
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No, the name got recycled. It's now a bootloader you hook up to the expansion port.

https://github.com/defparam/21FX


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PostPosted: Sun Feb 18, 2018 1:29 pm 
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Yeah I'm not really well versed in the history of all this SNES stuff. The MSU-1 would require significantly more hardware and complexities compared to the simplicity of migrating the 21FX onto a pass through device.

I am somewhat interested in the MSU-1, but it's hard for me to get a sense of what's required on the hardware side as most definitions are software focused and rather limited. Perhaps there's some better docs out there aside from this that I'm missing though..? The only hardware implementation is SD2SNES I believe, so I'd probably have to dig into it's sources to get a better grasp of the hardware.

The idea of supporting MSU-1 as a pass through device would be interesting though, especially if it allowed you to plug in an unmodified original cart like Zelda LttP and get CD quality MSU-1 audio injected via pass through. The idea detracts pretty far from the OP though...

Not sure I should be getting into this as I'm probably starting to hi-jack the thread here. But I have been putting more thought into the design of the pass through SNES device. Biggest benefit of putting the 21FX on a pass through cart is the bootloader no longer has to stomp over the cartridge's reset vector by means of bus conflict. The pass through device could disable the data bus output of the cartridge while it's injecting the bootloader's reset vector in place of the cart. Doing so would effectively require a buffer/levelshifter to be placed on the data bus to select which device is driving the data bus. I wasn't sure I would have the spare CPLD i/o to make that happen in a 5v tolerant CPLD.

That paired with my recent investigation into SNES expansion chips has me considering taking the idea to another level entirely. Going so far as to level shifting the entire cartridge connector and connecting up a 3v CPLD that would have the entire cartridge bus visible to it. Doing that would allow full address decoding and byte size granularity of if the cartridge, or pass through device drives the data bus. Going that far would be like a super game genie of sorts, allowing cartridge roms to be patched with a rom on the pass through. Would heavily depend on the expansion chip, and game, but it might even allow one to do things like play Yoshi's Island hacks if you had an original YI cart plugged into the pass through. Main motive for that being the SFX, SA-1, and SPC-7110 not being replicated by ANY flash carts to date. SA-1 would be the least likely to work with this type of setup due to it's code base being less defined. The pass through can only change the rom/ram being executed by the SNES CPU, not the cartridge coprocessor.

Anyway, safe to say this project is officially on my list but no clue when I'll make time for it. I don't want to keep byuu waiting too long for a simple version at least which may very well end up looking like one of my boards with a USB interface tacked on which would effectively meet the desires of the OP from what I gather..

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PostPosted: Sun Feb 18, 2018 4:37 pm 
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defparam was working on a passthrough cartridge version of the 21FX a year ago, so it'd be a good idea to find out what happened with that.


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PostPosted: Sun Feb 18, 2018 4:49 pm 
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Oh thanks for the info, I didn't realize that. I followed and replied to the tweet so we'll see..

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