TashTwenty: Single-Chip DCD (Hard Disk 20) Interface

@demik @tashtari I'm having a dog of a time finding 3.3v 250ma voltage regulators at Mouser that use the right package; would a 3.3v regulator that has a 150mA output be sufficient (example)? The draw on the PIC is only something like 80mA, but I wanted to be sure prior to ordering. The only 250mA regulators that they have stocked at the moment are DIP-style, so they're out of the picture, lol.

mdeverhart said:

@tashtari @warmech Thanks! I’m wondering if any of the PowerBook ROMs include support, which could be nifty especially for Duos since they have an external floppy port. TattleTech lists two .Sony drivers on my Duo 230, one of which has a Type of “XL Hard Disk”, and one that has a Type of “Floppy Disk/HD20”. They’re both located in ROM at the same address, for whatever that’s worth.

Anyway, I may build one of these for my SE; if I do, I may also see what it would take to build an adapter cable for the dock’s external floppy connector. Probably not a project I’ll get to anytime soon, but I’ll post an update if I do.

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Huh... that's interesting. Surely that didn't just completely fly under the radar all these years, lol... I'd be very interested to see if they are capable!

It does seem odd to have gone unnoticed. It could just be an artifact of how TattleTech is parsing the data. If/when I find out I’ll definitely post results.

mdeverhart said:

TattleTech lists two .Sony drivers on my Duo 230, one of which has a Type of “XL Hard Disk”, and one that has a Type of “Floppy Disk/HD20”.

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Bear in mind that the Duo 230 has a 68030, so assuming I'm right about the response speed, even if it has ROM support, TashTwenty won't work on it anyway.

Yep, that had occurred to me as well.

warmech said:

@demik @tashtari I'm having a dog of a time finding 3.3v 250ma voltage regulators at Mouser that use the right package; would a 3.3v regulator that has a 150mA output be sufficient (example)? The draw on the PIC is only something like 80mA, but I wanted to be sure prior to ordering. The only 250mA regulators that they have stocked at the moment are DIP-style, so they're out of the picture, lol.

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Yeah getting voltage regulator is rough at the moment. The voltage regulator is not used for the PIC but for the SD Card. A 250mA was used because old SD Card are bursting to that amount of current. Modern SD Cards don't (especially in SPI mode)

The one you linked will not work. Pinout for the MPC1700 is 1:GND, 2:Vin, 3:Vout. The AP7381 has a different pinout.

A pinout compatible one is the ALBIC S-817B33AY-B2-U. It's only 50mA but should work with modern SD cards.

On a side note, the PIC16F1825-I/P is on backorder on mouser until 2023, you may want to use the PIC16F1825-E/P instead (it's just a slightly more expensive version that can run up to +125°C)

Edit: here is a mouser basket if you want to double check. (I didn't buy this one yet)

demik said:

Yeah getting voltage regulator is rough at the moment. The voltage regulator is not used for the PIC but for the SD Card. A 250mA was used because old SD Card are bursting to that amount of current. Modern SD Cards don't (especially in SPI mode)

The one you linked will not work. Pinout for the MPC1700 is 1:GND, 2:Vin, 3:Vout. The AP7381 has a different pinout.

A pinout compatible one is the ALBIC S-817B33AY-B2-U. It's only 50mA but should work with modern SD cards.

On a side note, the PIC16F1825-I/P is on backorder on mouser until 2023, you may want to use the PIC16F1825-E/P instead (it's just a slightly more expensive version that can run up to +125°C)

Edit: here is a mouser basket if you want to double check. (I didn't buy this one yet)

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Thanks for catching that - I'd have missed that completely! I'll pickup the 50mA variant in the mean time. And yep, gonna have to go with the E/P PIC for now as well. Boy oh boy, I can't wait until semiconductor production catches up in... (checks notes) years, if ever.

warmech said:

Thanks for catching that - I'd have missed that completely! I'll pickup the 50mA variant in the mean time. And yep, gonna have to go with the E/P PIC for now as well. Boy oh boy, I can't wait until semiconductor production catches up in... (checks notes) years, if ever.

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You are welcome. Yep I can't wait either. Had to wait 2 months for PICs...

Anyway, let us know how your build goes ! We will be happy to assit you if needed. I've pushed more documentation to GitHub, and @tashtari pushed all PCB gerber files. You can find them in the release section (TTT_10.zip and DB19_IDC20.zip).

demik said:

You are welcome. Yep I can't wait either. Had to wait 2 months for PICs...

Anyway, let us know how your build goes ! We will be happy to assit you if needed. I've pushed more documentation to GitHub, and @tashtari pushed all PCB gerber files. You can find them in the release section (TTT_10.zip and DB19_IDC20.zip).

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Boards are already off to OshPark, so I'll make a will call pickup from Mouser sometime later this week at lunch and sit back until the PCBs arrive. Once I've got them, I'll update with photos of it in the HD20. I'm buying right angle 10x2 connectors to fit in the HD20 case, so it should go in just fine.

If you're feeling especially creative, you could mod the design a bit to make the daisy-chain port work. I don't know how much I've publicized this, but TashTwenty does support daisy-chaining another drive. (Another HD20 or a floppy drive.) You basically just put all the lines through from the cable except for the !ENBL line, which you connect to pin 13 on the PIC.

tashtari said:

If you're feeling especially creative, you could mod the design a bit to make the daisy-chain port work. I don't know how much I've publicized this, but TashTwenty does support daisy-chaining another drive. (Another HD20 or a floppy drive.) You basically just put all the lines through from the cable except for the !ENBL line, which you connect to pin 13 on the PIC.

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You bet I'm going to try that, lol!

warmech said:

You bet I'm going to try that, lol!

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Removing the J1 jumper will disable the !ENBL coming from the cable. Pin 2 of J1 go to the !ENABLE line of the PIC. Pin 13 is not connected on the Tiny board so you will gave to weld that directly to the PIC or something.

Genuine question: how are you wiring this inside a Rodime case ? Is there a standard floppy connector inside ?

demik said:

Removing the J1 jumper will disable the !ENBL coming from the cable. Pin 2 of J1 go to the !ENABLE line of the PIC. Pin 13 is not connected on the Tiny board so you will gave to weld that directly to the PIC or something.

Genuine question: how are you wiring this inside a Rodime case ? Is there a standard floppy connector inside ?

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Regarding the wiring: noted; I'll take a look when I get the PCBs in and make adjustments as necessary. Lol, I'll probably have questions, so I apologize in advance.

As far as wiring this up inside an HD20, here's the inside of my dead one. The floppy drive cable just... terminates straight into a 20-pin internal floppy connector; I would have assumed it used something more complicated, but apparently not. Since I don't want to mangle this control board (it works fine with my other working Rodime, so I know it's the HD itself that's bad) I'll probably pull a female DA-19 off one of my many irreparably dead IIsi boards and manually wire it up to test for now. Once - if - I get it working as a proof of concept, I may modify and expand the TashTwenty PCB to occupy a similar footprint to the business end of the control board and just have it be a drop in replacement, provided you can source a female DA-19.

HD20s are a dying breed; this would be a fantastic replacement if it was just a swap of the controller board.

warmech said:

this would be a fantastic replacement if it was just a swap of the controller board.

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That would be pretty neat. =D

Would love to be able to do with my HD20 what @warmech is doing with theirs. Mine is similarly dead; doesn't initialize, and attempts to revive with HD Diag have been unsuccessful...

tashtari said:

That would be pretty neat. =D

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Yep, need to scan eBay for HD20s now !

Update: I scored an HD20! Nonworking but in great cosmetic condition, ripe for a TashTwenty control board replacement.

More interesting update:

I decided to put the scope on the Classic II with my proven-to-work TashTwenty dongle thing. As expected, it didn't work. Unexpected, however, was the fact that it appears not to work not because the CII is failing to detect it, but because the firmware thinks the SD card has no partitions and so isn't responding. !ENBL goes low and the daisy-chain !ENBL output immediately goes low. Exact same board, exact same setup consistently works fine on my 512ke.

This is really interesting. Maybe it's something with the Classic II in general? With my particular Classic II? Something to do with power? A firmware bug triggered by some difference in behavior in the Classic II's ROM? I don't know. All I know is, I really want to get this into more people's hands, ideally people with access to a IIsi, IIci, Classic II, or one of the other setups where HD20 is supported on a machine faster than 8 MHz.

The total BOM needed to build one of my TashTwenty boards is:

• PCB
• PIC16F1825 (DIP), programmed with 20211128 firmware release
• "DB"-19 solder cup connector
• SparkFun level shifting microSD board
• 10 uF decoupling capacitor
• 10 Kohm resistor
• 7-pin 0.1" header
• 7-pin 0.1" socket
• 14-pin DIP socket

I have some parts on hand which I'm prepared to sell at cost (or at least my best guess at it), I believe I have enough to make:

• One complete kit ($20)
• Two complete kits minus the SparkFun level shifting microSD board ($14)
• Two bare-bones kits consisting of PCB and programmed PIC only ($4)

If you want to buy one, let me know. Shipping not included - I'm in the US - if you're in the EU, you're probably better off buying one of @demik 's, shipping in either direction is absurdly expensive. If you do buy one of mine, nota bene and be comfortable with the usual caveats: these are unassembled kits provided without guarantees or warranties, no returns, satisfaction not guaranteed, you should know what you're doing.

I'm waiting on boards to come back from OSHPark and will assemble one myself hopefully next week. I've got a Classic II that I can give this a go on.

Whilst digging into the Classic II issue, I noticed something interesting. The 'low' value on the MISO pin to the card (the one with the pullup resistor) was a surprisingly high 1.4-1.5 volts, and when plugged into the CII, the logic analyzer on my scope was reading it as flitting between logic low and high. Reports vary on what strength of pullup you need on the MISO pin, but I was using 10k. Swapped it out for a 100k and... now it doesn't work in the 512ke, either. D'oh.

The experiences I've had so far are making me feel like the reason it's not working in the CII is an electrical problem, not a firmware problem. Maybe I should stick to firmware and leave the electricity to others...

tashtari said:

Reports vary on what strength of pullup you need on the MISO

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Just a thought... now that you have a real HD20, perhaps connect it to the CII and put the analyser on it to see how the 'real deal' behaves?... I'm also gonna PM you re. your parts - I have various Macs I could test on (as well as a couple of HD20s, FloppyEMUs, etc...)