exxos's Atari, Amiga & retro forum

terriblefire wrote: 29 Oct 2020 13:31The most significant issue is how to select a floppy disk image.... options...

1. implement some kind of display a'la gotek.
2. some kind of OSD overlay (needs a board respin).
3. dont display anything.

alexh wrote: 30 Oct 2020 07:41

terriblefire wrote: 29 Oct 2020 13:31The most significant issue is how to select a floppy disk image.... options...

1. implement some kind of display a'la gotek.
2. some kind of OSD overlay (needs a board respin).
3. dont display anything.

When Jeff of HxC was creating the first stand alone FDDE we discussed many times the aesthetics of the interface. I thought multiple buttons and a screen plus butchering your case was not the way to go when you have a keyboard, mouse and TV screen. Jeff created a default boot disk, the Amiga version was named SELECTOR.ADF, with a native host program on it which is a file selector where you could queue your disk images. The information sent to the FDDE though the floppy disk interface. The only HW needed was one button (eject) to cycle through the queued disks and a long press to go back to default boot disk. The program for Amgas is still available and being updated and even the source for the command set is available I think because support for it was added to flashfloppy. Might be the way to go?

arkadiusz.makarenko wrote: 30 Oct 2020 12:41 I have cleaned project rebuild it tidy up some code and now works ok again. Don't have clue why this happened. :(

arkadiusz.makarenko wrote: 30 Oct 2020 16:49 @terriblefire
Have you happen to seen any source on how amiga floppy interface work? I would need to understand it a little bit better.

arkadiusz.makarenko wrote: 30 Oct 2020 19:57 So by reading and setting values from register we know what data to send, and then send it using /DKRD.
How do I clock this data?

When data is MFM encoded, the encoding is performed on the basis of a data
block-size. In the sector encoding described above, there are bytes
individually encoded; three segments of 4 bytes of data each, treated as
longwords; one segment of 16 bytes treated as a block; two segments of
longwords for the header and data checksums; and the data area of 512
bytes treated as a block.

When the data is encoded, the odd bits are encoded first, then the even
bits of the block.

The procedure is: Make a block of bytes formed from all odd bits of the
block, encode as MFM. Make a block of bytes formed from all even bits of
the block, encode as MFM. Even bits are shifted left one bit position
before being encoded.

The raw MFM data that must be presented to the disk controller will be
twice as large as the unencoded data. The relationship is:

1 -> 01
0 -> 10 ;if following a 0
0 -> 00 ;if following a 1

With clever manipulation, the blitter can be used to encode and decode the
MFM.