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Old 07 November 2006, 15:20   #24
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Join Date: Sep 2005
Location: melbourne
Age: 49
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Originally Posted by alexh
Having to have a Windows based PC within USB cable length of the Amiga/ST is a big drawback IMHO.

If it had a compact flash interface as well, for stand alone use, it would be great. But it would also be 10x more complicated and more expensive.

The FPGA has to be a lot bigger as it has to do the MFM conversion and the Compact flash file access. There are some home project prototypes in development that do this.

no need for complicated or expensive - I've suggested on the Torlus forums that the floppy image could be stored on the flash card as an already decoded image (RAW data or MFM data - whichever is more appropriate) - so instead of using the computer to decode and stream the data down the USB, the computer software is used to decode the ADF/DMS/IPF(Amiga)/.ST/.MSA(Atari ST) to a file then that MFM decoded file is auto-renamed to fit a 'slot' of up to 16 spaces (ie: is named 0disk, 1disk, etc. to edisk, fdisk (how many games etc. are more than 16 disks?) and those files can then be copied on to the removable memory card connected to the PC (or MAC).

A PIC could be used to select and load the disk image to the memory connected to the FPGA, then the current project's FPGA does the floppy emulation (no extra programming needed) and transparently loads the data to the Amiga or ST.

All that might need to be developed is the programming for the PIC and interfacing the PIC to a flash memory reader - which from the brief look I've had using google wouldn't appear to be too complicated, the modified 1541 virtual floppy schematic here has exactly what I'm talking about -

The only possible extras I can think of would be two push buttons (one for 'next' disk image and one for 'previous' disk image) and maybe a LED segment display to display which disk image is currently selected (0-f).

After the decoded disk image(s) is(are) copied to the memory card, the card is removed and inserted into the virtual floppy disk emulator and the Amiga/Atari ST powered on.

The floppy disk emulator by default looks for 0disk and loads it (if found), if 0disk isn't found, then it looks for 1disk, 2disk etc. until a disk image is found - if it cannot find a disk image then it returns the 'no disk inserted' signal to the floppy controller (and if you have a hard drive, then the computer boots from that as normal).

When a disk image has been loaded and the user presses the 'next' or 'previous' buttons - then the 'disk eject' signal is sent to the floppy controller, a small timed loop waits for however long the Amiga/Atari ST needs to register a disk has been ejected, the next or previous disk image on the storage card is selected/loaded into SRAM and the LED segment display is changed so the number/id of the selected disk is displayed; then the 'disk change/disk inserted' signal is sent to the floppy controller and the computer thinks that the disk has been changed and then tries to load it etc.

Originally Posted by alexh
You would not be able to support IPF images using a flash card, as SPS are keeping the IPF details a closed source project.
Well there's the stopper for having IPF access on the device, unless they decide to open the source or release an IPF decoding plugin for the MFM decode software (much like WinUAE and IPF possibly?).

Ultimately it'd be great to have write support in the floppy disk emulator as well - which might be quite easy if the FPGA supports writing to the SRAM - the PIC could then be used to take a 'snapshot' of the SRAM and copy it back to the flash card.

It's all just hypothetical at the moment, gotta wait until the final schematic, FPGA code and PC decoder software are released before I can start tinkering.

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