The Lynx FDC Project and issues

[oracle_jedi]

Último mensaje de la página anterior:

Also, the Lynx will NOT write anything to the HFE disk unless I force pin 34 low (short it). The HxC device works fine with the Amiga, ST and an old XT, so I think the HxC is fine. The Lynx FDC just seems supper fussy on the RDY line.

Having pulled all the ICs off the Lynx FDC to verify Frank's design, I realized I missed soldering pin IC13:11.

That was the RDY problem. Now it writes fine without shorting pin 34 of SKT2/3.

The HxC format problem is most likely due to the Lynx trying to format track 41. A real 200K drive will fail and the Lynx will determine it is a 200K drive. I think the HxC accept the track 41 format but since it is a 200K disk image it doesn't actually work. I might need an HxC firmware update to make this work, but it is not really a problem since I can make new blank virtual disks by simply copying the blank Lynx HFE disk back to the SD card.

[Womble]

Yep, my thoughts agree oracle on the HxC.

Its great that Frank's recreate works with the mods.

[jltursan]

I've finished the testing using a MB8877 instead the FD1793 and as expected, works fine. I've read files saved with the 1793 without errors, it's totally compatible.
This way you can power the controller using only a single source of +5V

[Womble]

Great googling the 8877 I came up with this:

https://francoisbasquin.blogspot.com/20 ... -disk.html

I was thinking at one point of porting the emulation of the 1793 I do in Pale onto the Propeller chip to interface with SD cards directly
without needing the HxC.

The prop has really fine control over the GPIO handling.

[jltursan]

Very interesting project; but seems there's no .ino available?. Although the MB8877 is still being sold and can be purchased more or less easily it's always a good alternative to have it emulated.

[Womble]

jltursan: I dont know whether it got off the ground but the information is in a nice format compared to hunting through the datasheet (assuming its correct info of course ) I can remember going round the houses in the 1793 data sheet creating the state machine for Pale.

I wonder whether the extra grounds on the 14338 chip are to avoid any current fluctuations that would occur if they left the grounds to one pin. Perhaps it was just to simplify board layouts with one ground per monostab.

[frankras]

Hi All

Just saw this discussion about the FDC.

I'm sorry for the errors in the schematic that I have made - it was made by measuring hole to hole on a new unpopulated board before I got the real schematic from John.

I will compare my DIPTRACE with the original and correct it.

Btw. You are always welcome to send me an email with questions or comments (frank@elborg.dk)


Best regards
Frank

[jltursan]

Welcome to the forum Frank!

The reverse engineering of this PCB is an unbelievable and hard work and you've done great!. There're only some errors that fortunately have been found and corrected, mine is working now with some patches over the first prototype PCB and seems to behave fine.

I need to double-check my cable pinout as it doesn't works stable enough with modern floppy drives, too many random errors while reading or formatting. Using older drives or a Gotek works great; so I think the PCB in itself is good.

Here's the fixed schematic:

original disk drive controller Camputers LTD 820008 FIXED.zip

(35.69 KiB) Descargado 7 veces

Btw, why not write a little (or not so little, you've a lot of history behind) presentation here for the people who don't knows you?

[Kyp]

Here's the fixed schematic:

¿Puedes convertirlo a PDF? No se con que se abre este archivo... Gracias.

[jltursan]

Es un esquemático de DipTrace y no permite exportar a archivos gráficos o documentos; pero mira a ver si vale esto:

https://www.altium.com/viewer?token=XkvNhxBi4kqctBId6zQfXhUl

Creo que permite descargarlo en formato Altium; pero es posible que también se pueda capturar como imagen. Si no te vale, sigo mirando a ver que puedo hacer, a las malas, puedo mirar de instalarme un driver de impresora PDF e imprimir el esquemático.

[Mike]

I have made a jpg file, if this is any help to anyone.

original_disk_drive_controlle_ Camputers_LTD_820008_FIXED.jpg

(908.97 KiB) No descargado aún

Its at 200 dpi resolution (big).

[Kyp]

El de Altium sale demasiado pequeño aunque maximize la ventana
Pero el de Mike se ve perfectamente

Gracias a los dos

[oracle_jedi]

I got the test boards back from OshPark on Friday, and today I bunked off work to test them.

They work!

Attached is a Gerber for the Lynx Floppy Disk Controller

Lynx Disk Controller 9A gerber.zip

(58.46 KiB) Descargado 3 veces

This design includes all the fixes jltursan, Pete and I were working through on this thread. You should be able to send this in to your favourite PCB fab shop and get back a PCB ready for you to add the components.

This design uses a single floppy disk connector, and is designed for use with an HxC or Gotek. There's no reason it cannot drive a really floppy disk, but given that it is a different shape to the real Lynx FDC, it cannot be used to replace a failed FDC in a real Lynx floppy disk drive. Also note this design uses a "standard" 3.5 PC floppy disk power connector which is keyed, so you won't make the same mistake I made with my real FDC, and send +12V down the wrong line.

The bypass caps are all 22nF/0.022uF. I think all other components are listed on the Silk Screen.

You still need a LynxDOS interface to use this. I think jltursan has a working Gerber for that.

Here's the blank board:

20201215_150342a.jpg (167.31 KiB) Visto 159 veces

Here's a populated board:

20201215_144123a.jpg (168.51 KiB) Visto 159 veces

Connected to the HxC and the Lynx

20201215_150550a.jpg (108.36 KiB) Visto 159 veces

I tested loading, saving and deleting files. So far no issues. I am assuming format still doesn't work on an HxC.

20201215_150435a.jpg (135.9 KiB) Visto 159 veces

And of course - Jet Set Willy on a real Lynx 96!

20201215_150540a.jpg (145.84 KiB) Visto 159 veces

Thanks to Frank Rasmussen, Pete Todd, jltursan and to Dropcheck on the AtariAge forum who helped me through the process.

Frank and Pete have made available many great LDF images for use with the Lynx.

And thank you to Mike for sharing so many great games.