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An Arduino-Based Parallel Port Hard Drive Troubleshooter

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AlexTheCat123:
Good news! I think I've managed to optimize things enough to keep up with the strobe, at least at the speed that the Lisa and USBWidEx pulse it. I don't know if it's fast enough for the Apple III and I don't have one to test it with, so I guess that will remain unknown. Luckily, I didn't have to resort to assembly at all; optimizing my C code was enough. I haven't had a formal education in computer science yet (I just started college a month ago), so many of the inefficiencies were probably stupid things that would have been obvious to anyone who has more experience with software development. Hopefully I'll have a prototype of the ProFile emulator going in a few days.

stepleton:
Wow, neat! So is the plan to interface with an SD card reader? All of these things are really very inexpensive!

AlexTheCat123:

--- Quote ---So is the plan to interface with an SD card reader? All of these things are really very inexpensive!
--- End quote ---
Yep! I got a little microSD breakout board off eBay for $3 and it handles all the logic level conversion for you, so I can just plug it into a header on my PCB and I'm ready to go. My goal with this project is to make it as cheap as possible and I think I'm doing pretty well with that so far!

stepleton:
Outstanding!

Now, it may be more of a programming exercise than an Arduino is ready to handle, but if you implement the protocol described at https://github.com/stepleton/cameo/blob/master/aphid/selector/PROTOCOL.md, your device will be compatible with the Cameo/Aphid selector program.

You know, you might be able to do it. I think you'd have to lean a lot on the filesystem on the SD card (assuming you choose to go with a filesystem at all): you could implement the key/value store by means of special files containing the data. But the Arduino's 2K of RAM may start to feel pretty cramped --- it looks like the libraries you'd need will consume half a kilobyte all on their own.

But that's probably getting ahead of things. A ProFile emulator made out of an Arduino is plenty awesome all on its own.

AlexTheCat123:
Once I get things up and running reliably, I'll definitely try to get the Selector protocol working! That would be a really nice addition to the emulator.

The Arduino Mega, which is what I'm using for this project, actually has 8K of RAM instead of the 2K of the other Arduino boards, so luckily RAM almost certainly won't be an issue! I originally wanted to go with an Uno or a Nano to make the device a lot smaller, but the ArduinoFile code just wouldn't fit in that limited RAM, so I had to go with the Mega instead. The emulator code should be somewhat less complicated than the ArduinoFile code since we don't have to deal with making a user interface, error-checking user input, and so on, so the emulator might actually be able to run on a 2K board instead of requiring the Mega.

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