> TI’s TXB0108 for this purpose as well, which has an automatic direction sensing feature that obviates the need for all of the direction logic that I mentioned above.
Yeah, don't use these guys. They have a tendency to swap translation direction in the presence of electrical noise, which means your input is now an output, cross-driving something. Sometimes everything survives just fine and switches back on the next edge. Sometimes the magic smoke comes out. And sometimes, if the stars align just wrong, you get an industrial accident.
This is one of those classes of parts that has hidden dangers and really should not be as prominently advertised as it is. They look simple, but they're for experts only. Don't use them unless you really know their failure modes and don't have another reasonable option.
These parts are bonkers. The ringing on its own outputs with a few inches of trace or (heaven forbid) a connector is regularly sufficient to self-trigger the automatic direction reversal. These things genuinely deserve the "experts only" label - they are close to unusable in the situations where you'd be most inclined to reach for them.
I've had them oscillate, though I don't remember the exact conditions, but they'd switch directions at very high speed, causing noise, causing them to oscillate.
Bunch of pulldown restrictions too, though if you pulled both ends the same way when not driven, that usually worked ok
- U6 and U8 need nearby decoupling. LVC logic has horrid power consumption during transitions, so best to feed it well if you expect any kind of transition rate out of these gates. It doesn't have to be explicitly dedicated to these parts but it needs to be physically close.
- That goes extra for the big fat WideBus 16-wide level translators. They have multiple power pins for a reason. They are vicious little devices. Decouple every last power input pin with its own individual capacitor.
- U6 outputs appear to have wrong bus directions? Probably not important (also maybe not a problem at all, I usually do Altium not KiCad)
- VBUS is not logic level, so you shouldn't use it as a logic signal if you want reliability (it will work... mostly... but also be weird sometimes), but you absolutely cannot drive multiple things with it and expect them to work (their input thresholds will be slightly different and you will be sad when they switch at slightly different times because it's moving slowly). Clean it up with a Schmitt trigger (1G17 etc).
- No ESD protection on the USB port. Do you want it to live? Try something like ECMF02-4CMX8, nice and simple to implement (mildly annoying to solder though).
- Whatever is going on with Q1 is poorly enough drawn that I can't understand it at a glance. Best to just draw these parts as two ordinary MOSFETS with A and B suffixes, then the circuits can be legible.
- On IC2 (why not U2?) lines 4, 5, 6, 7 are being cross-driven. Do not ground both sides, you will be sad. Ground the input sides and let the outputs be unconnected, because they're strongly driven by the chip. Or use resistors to pull things places if you must satisfy someone somewhere who loves that kind of stuff (medical! medical? medical.).
- U7 SENSE pin draws not-much current (~25nA) so no reason to burn power in that resistor divider
- Consider stuffing a big fat electrolytic or two down somewhere and making your PDN nicely damped.
Cool, I wish this article was available when I made my custom cartridge design :)
For my game Cubeat[0], I put an OPL3-L chip on the cartridge connected to the GB's otherwise unused audio-in pin, which allows for FM music in the game. For the MBC logic I just used a bunch of 7400 discrete logic chips. I'm hoping to finish this thing and get it published at some point since I think it's going to be a really cool little parlor trick for the GB.
I assume they mean you don't need to modify the device's hardware or hack any software – you just need to include a blob in your ROM's header (which RGBFIX will automatically insert for you, if you're using the RGBDS toolchain).
Plus, Sega v. Accolade killed that practice. I don't think anyone has tried to enforce it since.
Pretty cool idea to ship ram and disk space with the application. It makes a lot of sense when you think about it. Imagine if phones worked like that and you could buy a new cartridge every couple years when chip technology improves or if you want to run some hard-core application. Or if you want to attach a new type antenna. My mind is wandering now.
Modular phones have been proposed for ages now but seem not viable or useful. Having everything on sockets increases latency between chips and decreases reliability. Especially something that's getting banged around in your pocket all day.
And there isn't really just one thing that gets outdated on phones. You usually want a better screen, better camera, better CPU, more ram, new battery. And at that point why swap each one individually vs just buying a new phone. I guess you save on the metal case?
> And there isn't really just one thing that gets outdated on phones. You usually want a better screen, better camera, better CPU, more ram, new battery.
I can't help but notice that you don't mention the part that makes it a phone (e.g. the 2G/5G/Wifi modem chip). Maybe one should actually sell those as cartridges... Nevermind, that would be a PC-Card.
It's more like a separation between backend and fronend. All the hidden tech goes in the cartridge and your screen and touch inputs are your frontend. Most people like their UIs to stay consistent even when new stronger, faster technology comes around so idk man.
I think its a good idea too, however does there come a point there you're also limited by the hardware it is plugging into? You might be able to include faster RAM in the cartridge, but will it work as intended with the original board its being plugged into.
Could you attach faster storage if the underlying hardware its plugged into isn't changing. I guess you could but I don't have a lot of experience in that area.
You can do pretty much anything if the cartridge is advanced enough. At that point you just output a framebuffer from the cartridge the screen should show with no computation happening on the actual gameboy CPU.
People built cartridges which stream game footage from a PC to the gameboy and relay the inputs back to the PC to "play" GTA 5 on an original gameboy.
https://www.youtube.com/watch?v=pX1opw_gsBs
Sitting here at work negotiating on an increasingly complicated hotpatching system for microcontroller ROMs, I can totally see why it fell out of favor. It is a great help to have the whole application on chip ready to go, but people keep wanting to change things.
My Pokemon blue version went through the washer and dryer probably 20 years ago and it still works to this day. Talk about some hardware. I wonder if an SD card would take that sort of abuse.
Readit News
Yeah, don't use these guys. They have a tendency to swap translation direction in the presence of electrical noise, which means your input is now an output, cross-driving something. Sometimes everything survives just fine and switches back on the next edge. Sometimes the magic smoke comes out. And sometimes, if the stars align just wrong, you get an industrial accident.
This is one of those classes of parts that has hidden dangers and really should not be as prominently advertised as it is. They look simple, but they're for experts only. Don't use them unless you really know their failure modes and don't have another reasonable option.
Bunch of pulldown restrictions too, though if you pulled both ends the same way when not driven, that usually worked ok
- U6 and U8 need nearby decoupling. LVC logic has horrid power consumption during transitions, so best to feed it well if you expect any kind of transition rate out of these gates. It doesn't have to be explicitly dedicated to these parts but it needs to be physically close.
- That goes extra for the big fat WideBus 16-wide level translators. They have multiple power pins for a reason. They are vicious little devices. Decouple every last power input pin with its own individual capacitor.
- U6 outputs appear to have wrong bus directions? Probably not important (also maybe not a problem at all, I usually do Altium not KiCad)
- VBUS is not logic level, so you shouldn't use it as a logic signal if you want reliability (it will work... mostly... but also be weird sometimes), but you absolutely cannot drive multiple things with it and expect them to work (their input thresholds will be slightly different and you will be sad when they switch at slightly different times because it's moving slowly). Clean it up with a Schmitt trigger (1G17 etc).
- No ESD protection on the USB port. Do you want it to live? Try something like ECMF02-4CMX8, nice and simple to implement (mildly annoying to solder though).
- Whatever is going on with Q1 is poorly enough drawn that I can't understand it at a glance. Best to just draw these parts as two ordinary MOSFETS with A and B suffixes, then the circuits can be legible.
- On IC2 (why not U2?) lines 4, 5, 6, 7 are being cross-driven. Do not ground both sides, you will be sad. Ground the input sides and let the outputs be unconnected, because they're strongly driven by the chip. Or use resistors to pull things places if you must satisfy someone somewhere who loves that kind of stuff (medical! medical? medical.).
- U7 SENSE pin draws not-much current (~25nA) so no reason to burn power in that resistor divider
- Consider stuffing a big fat electrolytic or two down somewhere and making your PDN nicely damped.
Most of the links were already long-long-dead, but there were some cool inspirational projects on there.
For my game Cubeat[0], I put an OPL3-L chip on the cartridge connected to the GB's otherwise unused audio-in pin, which allows for FM music in the game. For the MBC logic I just used a bunch of 7400 discrete logic chips. I'm hoping to finish this thing and get it published at some point since I think it's going to be a really cool little parlor trick for the GB.
[0] https://nickfa.ro/wiki/Cubeat
While there's no region lockout, don't you need to pass the logo check?
Plus, Sega v. Accolade killed that practice. I don't think anyone has tried to enforce it since.
And there isn't really just one thing that gets outdated on phones. You usually want a better screen, better camera, better CPU, more ram, new battery. And at that point why swap each one individually vs just buying a new phone. I guess you save on the metal case?
I can't help but notice that you don't mention the part that makes it a phone (e.g. the 2G/5G/Wifi modem chip). Maybe one should actually sell those as cartridges... Nevermind, that would be a PC-Card.
Could you attach faster storage if the underlying hardware its plugged into isn't changing. I guess you could but I don't have a lot of experience in that area.
People built cartridges which stream game footage from a PC to the gameboy and relay the inputs back to the PC to "play" GTA 5 on an original gameboy. https://www.youtube.com/watch?v=pX1opw_gsBs
Keyboards can also survive dishwashing with gentle soap. So can motherboards