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

superjer2000

Well-known member
That's very strange - no response from the !CS line at all, not even to try to initialize the SD card? My first thought is to try swapping the PICs from one to the other - if the failure follows the board, maybe there's an issue with power; if the failure follows the PIC, then... maybe ESD? It'd be very strange if that were the case, but it's not impossible.
And it works!

I was beginning to second guess my soldering, but finding an issue would be too much of an ego blow to a dedicated vintage hobbyist!

The issue was I hadn't jumpered J3 on the Demik TashTwenty. Jumpering J3 allowed both my Transcend microSD card and the regular size Transcend SD card to boot my Demik TT.

So to summarize, both my TT2.0 and DTT work great with the Transcend cards I bought on Amazon. I was unsuccessful getting my Sandisk or other brands to work (error code 0x05) but given that changing card brands worked, I'll stick with the current PIC firmware.

Thanks again and hopefully my experience helps others.
 

tashtari

Well-known member
I did do some quick testing on a SE/30 I'm restoring with a ROM-inator ROMSIMM. Works great!
Excellent. =D
Speaking of uSD cards... I bought some brand new (but chinese-obscure branded - Lerdisk) uSDs off Amazon - in 512Mb and 2Gb capacity. NONE of them work. They format, I can copy files onto them, but they just don't work. FWIW, none of them work on my BlueSCSI either. 😑 After hitting problems, I checked out the AMZ feedback. Mostly positive, but quite a few complaints about problems on rPis... 🤔 So, I don't think this is a TT-specific phenomenon.
Hmm. I wonder if their firmware doesn't support SPI mode or something like that? I'm not sure if RPis use SPI mode, but that could account for them not working on your TashTwenty or BlueSCSI.
EDIT: Doesn't seem like RPis access the card using SPI mode, maybe they don't support SPI and have some other firmware-related incompatibility as well. In any case, buying SD cards online is a fiddly business...
The issue was I hadn't jumpered J3 on the Demik TashTwenty.
Aha, that'll do it. J3 connects !ENBL on the connector with !ENBL on the PIC, so without it, TashTwenty will never know it's being talked to. Glad you figured it out!
 
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jajan547

Well-known member
Just built mine and it works great on my Macintosh Plus!
 

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tashtari

Well-known member
I'm looking to get rid of some of my inventory now that the project is relatively mature...

I have a TashTwenty Rev 2 board with SD level shifter, latest firmware, assembled and tested, $17.

I also have a TashTwenty Rev 1 board, fit using wire jumpers to a slightly cheaper level shifting SD board from AllElectronics; it might not be pretty, but it's assembled and tested, $13.

Still no full kits, but I've got plenty of PCBs for TashTwenty Rev 3 and TashTwenty Tiny for anyone wanting to do their own builds, as well as programmed PICs. I also still have some of the blue Hammond cases for anyone who's already built a TashTwenty Tiny.

Let me know if anything on offer interests you!
 

warmech

Well-known member
Oh dang! This reminds me, I need to draw up an HD20 replacement PCB! Almost done with the Lisa 2 CPU card; I'll start this back up once that's done.
 

tashtari

Well-known member
Okay, both are sold, thanks everyone who expressed interest! I still have plenty of PCBs and PICs for anyone wanting to do builds of their own, and one remaining Hammond case for anyone who's built a TashTwenty Tiny but hasn't housed it yet.

This reminds me, I need to draw up an HD20 replacement PCB!
Looking forward to that!
 

Zhinü

Well-known member
When do you guys think the GUI to mess with the drives will be made? I do want to alter up my drive setup (and change cards possibly) but don’t want to fuss with Linux just to change it up.
 

tashtari

Well-known member
When do you guys think the GUI to mess with the drives will be made?
I'm not working on a GUI, myself... GUI programming has never been my strong suit. If you're okay using a command line utility, though, you can check out the Python script I wrote for generating images here, it works fine on Windows, you just need to install Python.
 

warmech

Well-known member
Looking forward to that!
As promised:

tashtwenty_mega_top.png
tashtwenty_mega_bottom.png

Hope you don't mind, I took some creative license with the name.

Instead of two LEDs indicating power and activity, this version XORs /ENABLE and +5V to one green LED to simulate the effect of the power LED on the HD20 blinking when activity is going on. This also eliminates 75% of the LS08 workload, lol. If anything stands out as egregiously wrong, let me know and I'll make any corrections as you see fit. One thing I did have a question about, though: originally you had said that these could theoretically be daisy chained if /ENABLE were tied to pin 13 on the PIC - is that still the case? If so, I can mod that in really easily. I went ahead and passed all the pins through from the cable to the connector, so it should work with that one change I'm guessing? Also, if it's tied to pin 13, does it need to be unrouted from any of its other connections (pin 2 on both the PIC and LS86)?

Edit: I'm also considering integrating part of the HDD Clicker for aesthetic effect; if we're simulating the activity light, might as well slap in some simulated seek action noise as well, lol.
 
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tashtari

Well-known member
As promised:
Cool! I'm excited about having a new TashTwenty design out there, and I love the name.

To answer your question, pin 2 on the PIC is !ENBL2 in and pin 13 is !ENBL2 out. Daisy chaining DCDs is accomplished by the Mac pulsing PH3 - !ENBL2 out starts high, and the currently selected device disables itself when it sees the pulse on PH3 and asserts !ENBL2 low for the next device. This way, the Mac can select the first device by asserting !ENBL2 low, the second by asserting !ENBL2 low and pulsing PH3 once, the third by asserting !ENBL2 low and pulsing PH3 twice, &c.

Thusly, to make the daisy chain port work, you need to pass through all the lines from the main connector, except !ENBL2 (pin 17 on the 19-pin D-subminiature), which should be connected to pin 13 on the PIC.

Speaking of the daisy chain port, since PC-mount 19-pin female D-subs are nearly unobtainium, what about making it an option to stuff a full-size SD card slot that's accessible through the back window of the HD20 where the port is? Can the footprints fit over one another on the same board, or would it be necessary to make two separate board designs? Maybe a little riser board would make it work?
 

tashtari

Well-known member
It looks like you carried over the J3 jumper from demik's board - that shouldn't be necessary in this board if the objective is to be a drop-in replacement for the HD20's board. The purpose of J3 was for situations like the IIvi/IIvx/LCII, where !ENBL2 as a signal wasn't broken out to any connector and had to be accessed by clipping or green-wiring onto a leg of the SWIM chip.
 

micheledipaola

Well-known member
So here's the noob asking (probably) dumb questions: to restore my hd20 do I need either a tash20 and this tash20 mega card?
 

warmech

Well-known member
So here's the noob asking (probably) dumb questions: to restore my hd20 do I need either a tash20 and this tash20 mega card?
Not dumb at all! The Mega is a re-implementation of tashtari's original design, so you would only have to have it and a small bill of materials (that are largely the same as the original) in order to make it work. The PCB is powered by the floppy port itself, so you wouldn't even need an additional power cable to drive it.
 

Corgi

Well-known member
When do you guys think the GUI to mess with the drives will be made? I do want to alter up my drive setup (and change cards possibly) but don’t want to fuss with Linux just to change it up.
This has inspired me. I've been trying to find a tiny project to re-hone my C# skills. Used to be a professional C# dev but haven't touched it in over 10 years. No promises this will ever be done, but I've drafted a UI in Visual Studio; what do you think?
 

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tashtari

Well-known member
I've drafted a UI in Visual Studio; what do you think?
Looks great! I'd love to see this come to fruition, I know my Python script isn't quite what you'd call convenient, plus it'd be great to have an integrated function to convert conventional graphical formats to 32x32 ICON resources.
 

micheledipaola

Well-known member
Not dumb at all! The Mega is a re-implementation of tashtari's original design, so you would only have to have it and a small bill of materials (that are largely the same as the original) in order to make it work. The PCB is powered by the floppy port itself, so you wouldn't even need an additional power cable to drive it.
This sounds great, really looking forward to kmowing how to get a Mega and all the rest 😎
 

micheledipaola

Well-known member
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