MottZilla (Archived from PSXDEV.net) | Posted on 2022-03-06 19:45:43 UTC
You might want to design a version that does do proper voltage level translation. Often things do work without shifting between 5v and 3.3v levels but it could be causing stress on internal components and if it's in a custom IC that's going to suck if it results in premature failure.
The 3D model looks cool. I suppose a 3D printed casing would follow. Then you've got your whole home made rom cart.
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prochazkaml (Administrator) | Posted on 2022-03-06 20:39:50 UTC
Thank you for the feedback!
The premature failure worries me as well, and I am shocked that ROM carts back in the day did this.
I had a quick thought, and wouldn't a simple voltage divider get the 5 V coming out of the EEPROM down to ~3.5 V quite easily? E.g. 10k going to the output pin, 22k to GND and the middle to the PlayStation? That would yield ~3.4 V, which should work, right?
And you bet there's a case coming, but that's not high priority at the moment, as I am still trying to figure the actual circuit out. 😀
MottZilla (Archived from PSXDEV.net) | Posted on 2022-03-06 22:01:44 UTC
I'm not shocked that an unlicensed product would do such a thing. Especially the cloned versions.
The voltage divider might work but then you'd need a lot of them as you'd need one for each signal. Might make more sense to use a dedicated IC. But whatever works.
prochazkaml (Administrator) | Posted on 2022-03-07 06:04:02 UTC
Eh, fair enough. Still a crappy practice though.
I know that a level shifter IC would be ideal, but for the time being (before I get one), the resistors should work fine.
prochazkaml (Administrator) | Posted on 2022-03-10 18:25:49 UTC
Or I can just use a 3.5 V-compatible EEPROM (or rather Flash) to begin with. The SST39VFXXX series looks like a good candidate, since it's quite cheap, it appears to have less latency than the SST29 series and most importantly, it's currently in stock available to buy immediately from all major distributors (Mouser, DigiKey, Farnell – they offer really low shipping rates to the Czech Republic (around 7 €), so it has been the most convenient one for me in the past). Just look around the internet for "SST39VF" (the "VF" is quite important here, as it means that the chip is rated to run at up to 3.6 V), you can find them very easily.
The highest capacity one from the series (512 kB) goes for just 2 € including VAT. So if I get my EEPROM working, I'll definitely buy a few of these and I'll redesign the PCB to fit a PLCC socket for these chips instead, removing the need for the on-board voltage regulator.
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