New project: vDisk - sneak preview :-)

Por lintweaker

Master (159)

Imagen del lintweaker

02-11-2019, 10:34

I've finally made my own MSX cartridge! In it's first version it will function as a virtual disk drive where a Rasperry Pi Zero will serve up disk images which can be read from the MSX.

The design is based on smbaker's
Pi virtual floppy for ISA/XT

With this hardware there are lot's of possibilities for future expansion, like using it as a MSX networkcard (with a Pi Zero W),

Now all I need to do is write a MSX Disk BIOS :)
The flash on board (currently not fitted) has a DOS2 mapper and can handle 1 and 2 Mbit flash ROMs.
Using Nextor with a Nextor driver would also be a nice option.

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Por sdsnatcher73

Hero (663)

Imagen del sdsnatcher73

02-11-2019, 18:12

Cool! We cannot have enough disk replacement options, if you ask me...

Por lintweaker

Master (159)

Imagen del lintweaker

02-11-2019, 19:12

The more the better :-)
I quick read test using assembly in WBASS2, reading all 1440 sectors of a 720k disk, seems quite good.

Por Pencioner

Paladin (996)

Imagen del Pencioner

02-11-2019, 22:40

sdsnatcher73 wrote:

Cool! We cannot have enough disk replacement options, if you ask me...

Still, i'm more interested in other possible uses of it Smile Would be useful to have some Pi power to have a collaboration between it and MSX

Por ToriHino

Champion (384)

Imagen del ToriHino

02-11-2019, 22:57

Pencioner wrote:

Still, i'm more interested in other possible uses of it Smile Would be useful to have some Pi power to have a collaboration between it and MSX

Something like this ?

Por Manuel

Ascended (15832)

Imagen del Manuel

02-11-2019, 23:11

Reminds me a bit of Nowind...

Por Pencioner

Paladin (996)

Imagen del Pencioner

03-11-2019, 02:00

ToriHino wrote:
Pencioner wrote:

Still, i'm more interested in other possible uses of it Smile Would be useful to have some Pi power to have a collaboration between it and MSX

Something like this ?

Correct. I had big hopes for that one (i have the prototype from first batch). But it has been designed in a way which made programming on both sides quite uneasy, so i'm looking forward for this one

Por lintweaker

Master (159)

Imagen del lintweaker

09-11-2019, 12:01

I am still waiting for parts to arrive so I can verify that the DOS2 mapper part works.

Some more info on the design:
I am using a 2k Dual Port SRAM which can be read and written to from both MSX as the Pi side.
By writing to a mailbox address from the MSX, the Pi is triggered there is work to be done.
I've mapped the 2k SRAM in page 0 in the MSX side, this way page 1 (4000-7fffh) is completely available for BIOS code.

Por zPasi

Champion (474)

Imagen del zPasi

09-11-2019, 18:12

For just a disk drive, a little bit overkill. I bet there is enough power in the PI Zero to handle the whole thing, without the need of other chips than voltage shifting buffers.

Some years ago I made a disk drive / memory mapper thing from an STM32F4-Discovery board. It has 5 V tolerant I/O:s so there is not even voltage shifters.
Picture in Dropbox

However, your new board has potential for much more. Definitely very interesting a project!

Por lintweaker

Master (159)

Imagen del lintweaker

29-11-2019, 11:39

Made some progress. The board is now fully populated and the mapper function works (not yet in use).

The BIOS is coming along as well, I can now boot from the vDisk and execute/read files.
It is not the speediest interface, on my Turbo-R I get 55kbytes/s using 'SCAN.COM' in DOS2. Maybe it will get a bit faster with some optimisations on both the MSX as the Pi side.
The Pi has to manipulate individual pins to read and write to the memory. Not the most efficient. (future testing with a microcontroller is planned)

This weekend I'll hopefully complete the write function so it's a fully working disk interface :)