Epson PX-8 Disk Drive emulator

[bdk6]

First post. Maybe it will be useful :D

I've had an Epson PX-8 since it first came out. I never was able to get a PF-10 disk drive for it. I finally, after almost 35 years, built a substitute. It uses an SD card for storage. The writeup, schematic, and arduino code to build it is at http://wrcooke.net/projects/pfbdk/pfbdk.html
I plan to do more with it when my interest rolls back around to it. Any feedback would be appreciated.

 

[alank2]

Looks good; very nice!

I especially like the comment "I want this to be a quick and easy project so that it actually gets done" - that is one issue I have, starting a project and not finishing it!

 

[bdk6]

Thanks!
If you look around on my site you will see a lot of half-finished (or less) projects. There are a LOT more in the shop that aren't written about. I actually managed to "finish" that one.

Will

 

[GeoffB17]

Yes, interesting.

Might be useful for my HX-20. I've got the TF-20 drive, which I believe still functions (as per the clicks it makes when I start it up) but it seems NOT to communicate with the HX. I assume I'd still need to sort this out (maybe some dodgy connections at the HX end of the link) as I understand your unit uses the same Serial Link.

Another change would be the fact that the HX setup has the 4 disk drives as A, B, C and D. Also, the HX loads the disk software from the A: drive disk onto the HX (extensions for disk BASIC).

Evern so, if it would work, it would be a help. The TF unit is great if it works, but it's pretty heavy, and certainly NOT portable!!

Geoff

 

[bdk6]

Hi Geoff,
This device won't really work with the HX-20 as-is. Although the HX uses the same serial protocol, it uses a lot of commands that are much more complex. The PX-8 essentially just reads and writes raw sectors, since that is all CP/M wants. But the HX expects the drive unit to handle the filesystem itself. The filesystem is very similar to a CP/M filesystem, but the commands are all handled on the drive unit. For instance, the HX will send an "open file" command, with a file name, and the drive will return some status information and open / create the file. On the PX, CP/M handles all that and just tells the drive which sector to read and write. It is certainly possible to add all that, but I had no need (nor any way to test it) so I didn't try. If you want to have a go at adding it I can provide either links to the documents you'll need or the docs themselves.
I can't remember off the top of my head, but I'm pretty sure the computer itself decides the drive letter. The first drive unit can have 1 or 2 drives (not on the PF-10, it can only have one drive per unit) and the second unit can have 1 or 2. The computer addresses the first drive on the first unit as 0,0 and decides what drive it will be (A, B, C, D, etc) So that shouldn't require any change.

Will

 

[GeoffB17]

Pity, getting too complicated.

I'd forgotten that the PX is essentially a CP/M machine anyway, which makes quite a difference as you point out.

Yes, the HX knows nothing about any of that. The TF unit (with 2 floppy drives always) loads CP/M from the disk and becomes a pretty normal CP/M computer. Very limited BIOS, almost normal BDOS, I don't remember about the CCP, and then loads the link prog into the TPA and runs that. This last prog takes care of processing all the commands from the HX, and sends the data back.

Even the FORTH system I wrote to access the disk sector-by-sector needs the link prog running to the TF, the ROM code in the HX does VERY little without the system in the TF.

So prob all not possible.

Geoff

 

[Martin Hepperle]

Yes, interesting.

Might be useful for my HX-20. I've got the TF-20 drive, which I believe still functions (as per the clicks it makes when I start it up) but it seems NOT to communicate with the HX. I assume I'd still need to sort this out (maybe some dodgy connections at the HX end of the link) as I understand your unit uses the same Serial Link.

Another change would be the fact that the HX setup has the 4 disk drives as A, B, C and D. Also, the HX loads the disk software from the A: drive disk onto the HX (extensions for disk BASIC).

Evern so, if it would work, it would be a help. The TF unit is great if it works, but it's pretty heavy, and certainly NOT portable!!

Geoff

Geoff,
for the HX-20 you might be interested in trying my display and disk emulator software running on a Windows or Linux computer.
See https://www.mh-aerotools.de/hp/hx-20/index.htm
The software is written in Java, so you need a JRE (Java Runtime Environment) for your computer.

Martin