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Thanks. =D I think @demik deserves most of the credit for this one, though. The firmware was an interesting challenge in some ways, but his work on the analog side of this project was considerably more complicated...

Forgot to update this thread, in case anyone was watching and missed it - @demik and I have released TashRecorder!

Oh, right, the code... https://github.com/lampmerchant/ps2-to-plus-keyboard

I'm sure someone's done this before, but I enjoyed the challenge (I used all but 61 words of program memory and all but 4 bytes of SRAM!)... I made some firmware for the PIC12F1501 that lets a PS/2 keyboard be used with a Mac Plus or the other Macs that used the phone-cord keyboard. It makes...

Elevate your game! Introducing... TashPad! Elevator Pitch It's a converter that makes a Super Nintendo/Super Famicom controller appear to an ADB Macintosh as a Gravis Mac GamePad. Used with the GamePad's control panel, it can be used to play all your favorite Mac games. I made the...

Got my answers from @Scott Squires - thanks!

Ah, I see. It's possible... it's even possible that it would change depending on the OS, I suppose I'm just hoping it doesn't.

Not that I'm aware of. I'd be happy with the results from whichever one you have to hand.

I find myself in need of someone to perform a couple of small experiments for me... Experiment 1: Open Key Caps or something else with a text box that supports arrow keys Hold down the shift key Hold down the keypad +/left-arrow key until it starts repeatedly inserting + signs While still...

Do we know that the official LocalTalk transformer has a higher DC resistance? (I don't know how to test this, and I don't have a LT dongle anyway.) Because the official schematic definitely has TxD± being fed directly into the transformer without a series cap...

This could be a cool project if anyone wants to take it up. My only Mac with a comms slot has it occupied by an ethernet card, though... I'd like to better understand this as well. I think the transformers provide true isolation between the bus and the devices connected to it while the...

I wrote some firmware this morning for the 1704, it uses a fixed-length loop that gets the clock in the ballpark (359.2 kHz, says the scope) if not as accurate as the 1501 with its NCO. Like the 1501 firmware, it also does 2x oversampling and has a LUT in case some manner of compensation is...

Status update. So, a few iterations later, I have some firmware for the PIC12F1501 that's about as densely packed as I can get it. Besides generating the clock and both RxD+ and RxD- (so no RS422 IC is required), it does 2x oversampling and has a 512-position lookup table that can be selected...

Just a tiny bit more... the spec sheet for the PIC12F1501 says typical supply current is 1.09 mA, max is 1.7 mA.

Put up some two-packs of these for sale for $7, BYO pigtail:

A little more story... I went hunting for trouble and asked in ##electronics on Libera about how I could improve the shape of the waveform being output by the 2N3906, and we determined that the 2N3906 I was using either was defective, counterfeit, or not a 2N3906. Weird. At @demik 's...

Aha! Switched out the 3.3 KΩ resistor with a 470 Ω resistor and the waveform actually dips below zero for a reasonable time now. The waveform is still kind of pointy at the bottom, but it works well enough to send a test sine wave to SoundEdit. Thanks @ymk ! I'd be happy to hear any...

Tried building and running this circuit with a test PIC (not the 12F1501 yet) and it doesn't seem to be having quite the desired effect: The scope is reading the value of HSKi from the collector leg of the transistor, the logic analyzer's HSKi line is reading the value of RA2. The fast rise...

Hmm... so would this work? Here, RA2 on the PIC is generating the clock signal, and RA5/RA4 are outputting opposite signals (so a true negative voltage isn't necessary there). I feel like some protection circuitry is necessary in case TxD+ goes negative... a diode of some kind between TxD+...

The important bit of the patent appears to be: The transformer I'm using has a max interwinding capacitance of 20 pF, and a max DC resistance of 0.8 ohms, no word on the voltage isolation or the number of turns or the wire gauge. As @cheesestraws pointed out before, though, the fact that...