Floppy emulator

[tnt23]

Umm, I really have no idea now.

[tnt23]

Still no news here Another project still keeps me busy.

Good thing is, that project is based on a similar chip, and this makes me believe it won't be too hard to switch back to my floppy emulator.

[tnt23]

Ooh! Do tell! What is it?!  :-)

 - Ali

It's a piece of hardware dealing with another industry standard pieces of hardware :-) Nothing fascinating, just that sort of job you make your living with.

[tnt23]

Wow, have just closed browser window with lengthy reply by accident

In short, I haven't put the project aside, although I wasn't able to update it for a while.

Here's a nice new LCD I'm considering to include in future design: it is a cheap COG 133x65 LCD with I2C interface.

Merry upcoming Christmas (and a Happy New Year :-))

[tnt23]

InTheSand wrote:

Looks good, and a reasonable resolution/size on that... How cheap is "cheap", and going off-topic a bit, how easy is it to interface one of those to an old 8-bit Z80 or 6502-based system?

Well, I got it for $6, plus bought two LED backlight modules to try, green one (shown) and white, $4 each. Not very expensive I think.

Driving i2c is not difficult, you'll only need 2 wires - clock line and data line. Everything should be done in software, and you must not exceed 400kHz barrier when talking to the indicator. You may wish to check this link for schematics and i2c software drivers for Z80.

[tnt23]

Fester wrote:

Would this project work in a 2000? I assume it would. Yes, keep it alive. I'm very interested in it.

Fester

I guess it should as soon as 2000's drives are ordinary DD ones.

[tnt23]

Not only Dennis' Minimig is an outstanding project, it also gives the rest of us good kick of inspiration and creativity

So I've finally managed to route the new board, with most, if not all, possible enhancements and future expansion possibilities (i.e. buzzer and fifth button  :lol: ). The picture can be seen here. (It doesn't show silk unfortunately, which has some nice artwork :-))

The boards are expected to arrive by the end of the week, and then the code will have to be rewritten for the new design. The MCU is faster now (16MHz instead of 8Mhz) There also is a possibility of adding Write support as all the necessary signals from the floppy bus have now been routed, too.

[tnt23]

IDE socket is there to help interfacing to CompactFlash in the future

[tnt23]

gizmomelb wrote:

Is it possible to interface IDE to the floppy port, or does it connect elsewhere on the motherboard as well?

It doesn't - it can only be used by emulator's MCU for CompactFlash access.

[tnt23]

@gizmomelb

You've made a good point BTW. Since the IDE interface in the emulator is just a bunch of I/O pins and is (or rather will be) done in software, part of it can be reprogrammed if it is not used.

For example, its high 8 data lines used for 16-bit IDE access can control a real floppy for example. Like dumping ADF to a real floppy, how does that sound?

I just got my boards from the factory, here's what they look like. Let the tinkering begin! :hammer:

[tnt23]

Just bought an IDE/CF converter board. Plugged it in, wrote some quick and dirty IDE code, fixed a couple of issues. Surprisingly, it works.

http://www.amiga.org/gallery/index.php?n=1921=5

[tnt23]

AJCopland wrote:
Wow that's a nice job you've done there. Is everything fully functional how you wanted it to be now?

Andy

LCD works, as well as the very basic SIMM support. I haven't ported SD/MMC part, and haven't even tried floppy bus interface yet. Still plenty of work to do.

[tnt23]

@adolescent

Yes, it is quite possible. Altough my adapter works with standard 'missing' pin 20, it can take +5v from it (settable by adapter's jumper). A jumper or optional zero ohm SMD resistor can be added in new revision of emulator's board.

My IDE socket is of plain 40-pin IDC type.

[tnt23]

Folks,

I would like to apologize for not posting any updates on the project. In fact, there simply haven't been any for quite a while.

Now for the good news. User interface is somewhat usable now. It still takes 16 seconds for ADF to load; if I find a way to cut it down further I will. A bunch of PC formats has been added, among them 720K and TR-DOS.

And what I am really excited about is this: write mode! The emulated floppy can not only be read, but formatted and written, too. The top level code for dumping the changes back to the flash is still to be worked out, but the low level write support seems to be working properly. (At least Linux' fdformat command takes it for real.)

A slightly redone board has been ordered, with some fixes (and possibly few bugs), able to accomodate LCD's backlight module. I am hoping to populate it in a week and tell you how it goes.

[tnt23]

@rkauer, thanks
I was thinking about adding boot loader to the emulator, so that its firmware could be updated via the same SD card. Otherwise it would require a JTAG capable programmer and software to reprogram the MCU.

[tnt23]

@FrenchShark

- No, I let output signals float. There is a 3-state buffer between my MCU and the bus, and when the emulator is not accessed, it switches its outputs to Z. I simply didn't care much as it worked for Amiga and PC. I guess both have own pull-ups to accomodate any floppy (with or without line termination).
On the Atari ST, however, the emulator failed as there seemed to be no internal pull-ups. I have added a few in a new revision of PCB because of that ST case.

- My ATmega256 runs at 16MHz. For DD MFM flow, every bit takes 2us, or 32 one-clock 62.5ns instructions. Here is how the output looked in early designs: http://milliways.chance.ru/~tnt23/amiga/mfm.jpg
Now it is much the same, only the "1" are wider.

- I don't do write precomp, mainly for the fact I am not aware of it Can you tell a few words on it?
There is an IDE/Compact flash port in the emulator, which is completely software driven. If I ever manage to use it to attach an external FDD for 'ADF Bakery', I will probably have to deal with write precompensation.

- As far as I understand, HD Amiga floppies deliver the same bitrate of 500 kbytes/sec, only INDEX pulse comes every 0.4 seconds instead of 0.2. If so, chances are good for that specific HD implementation to do on my current hardware.
PC HD can hardly be done on it with 1000 kbit/second flow.

BTW, Amiga Floppy Project (http://www.techtravels.org/amiga/amigablog/) also is based on Parallax chip.