Apple Disc II emulation possible?

[Dietrich-L]

Maybe it‘s a crazy idea, but might it be possible to adapt flashfloppy to be able to read/write Apple II disks? I know of course, that these systems used GCR. But they used mechanical identical drives and i understand that greaseweasle can read apple disks.

What do you think?

Dietrich

[rittwage]

This exists on the HxC firmware for the Gotek.

[keirf]

The main thing is to know the assignment of Apple pins to Gotek pins, and handle the phase inputs for the stepper motor. With assistance from an interested user with electronics knowledge and a cheap scope or logic analyser this would not be too hard.

[keirf]

Sounds good to me. It will take time, since I have no direct access to an Apple II. But your help is invaluable, and we will get there!

[philpem]

I've been watching the updates on this - I have an Apple II Europlus with Disk II controller and can set it up with a Gotek for testing if it would help.

[junkjunker]

I've been watching the updates on this - I have an Apple II Europlus with Disk II controller and can set it up with a Gotek for testing if it would help.

Sounds like you two are geographically closer than I am too. Testing could happen in more real time than from so many time zones away.

[keirf]

You don't escape that easily @junkjunker 😉

Phil, best help would be to convert a few PO or DO files to HFE using Greaseweazle command line above. And then try to boot those in latest Apple2 firmware above, and try some writes too. That would get us a second view point.

If you need further instructions just let me know!

[keirf]

Just to keep this going, I did finally download and take a look at @junkjunker's ProDOS images. It's weird that Greaseweazle tools will decode the whole disk fine, but HxC apparently doesn't like the overwritten sectors -- it colours all of them red. I wonder what it doesn't like about them, and whether it's relevant to the Apple2's slow writing/rewriting.

EDIT: Scrub that. With the latest version of HxC all sectors are green.

[chrispoacher]

Hopefully if this works it will allow Roland D20 to work also as it has a similar protocol as Apple although wired bescokely.  :)Chris PoacherSent from my iPhoneOn 13 Oct 2023, at 18:32, Dietrich-L ***@***.***> wrote: I will try that in the next weeks - busy times .. —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[dl6lr]

Am 28.05.2024 um 14:54 schrieb Keir Fraser:

The problem is that WDATA is toggling on each flux reversal rather than pulsing on each flux reversal.

AFAIK Apple II used GCR encoding (not FM or MFM) and the WDATA line was somehow directly coupled to the head. So flipping the level writes a flux reversal. I assume this is different from "normal" disc interfaces, where a pulse writes a flux reversal. The read head however differentiates the flux reversals, so pulses as usual are present on the RDATA line. Message ID: ***@***.***>

[junkjunker]

I found this info which corroborates your explanation:
IWM Signal and Bus operation Description
RDDATA The serial data input. The falling transition of each pulse is synchronized by the IWM.
WRDATA The serial data output. A transition occurs on this output for each one bit.

[Dietrich-L]

I commend Keir and junkjunker for their efforts. I wish I could support you more, but alas ... too many other urgent matters.
However I found in my cache a schematic of my ehring electrinc FDC4 controller for the Apple II. This controller allows to use shugart drives and Apple drives even in mixed configuration. The interesting part might be, how they converted Apple signals into Shugart signals.

S1,2 activate the Shugart IF, S4 switches from single side to double side (double side must be supported by a patched DOS 3.3

I sincerely hope, this helps and keep my thumbs pressed for succes of this fine project.

Dietrich
ehring FDC4 schematic.pdf

[keirf]

One useful book I just found is Understanding the Apple IIe, which has a fantastic chapter on the FDC. It builds up to the logical track format. I think the only thing it's missing is how the sector checksums and data encoding exactly works. I haven't found any documentation on that for the old GCR 5-and-3 format. I doubt that's common though?