flashx20 - Floppy and screen for the Epson HX-20

[allison]

On 12/16/2018 11:39 PM, Will Cooke via cctalk wrote:
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> On December 16, 2018 at 11:14 PM allison via cctalk <cctalk at classiccmp.org> wrote:
>>> On Sun, 16 Dec 2018, Norbert Kehrer via cctalk wrote:
>>>> I have not tested it, but I suppose, that also the PX-8 and PX-4 used
>>>> the protocol,
>>>> because the protocol specification defines the following device numbers:
>>>> - HX-20: 0x20 (probably also used for the HC-20)
>>>> - PX-8:  0x22
>>>> - PX-4:  0x23
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>> PX-8!
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> A subject dear to me.  I still have the px-8 I bought new (borrowed the money from my sister) as a young man in 1984.  Alas, I could never afford the PF-10 disk drive.
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>>> However, the PX-8 3.5" had 40 cylinders, with 67.5 tpi, instead of the
>>> common 80 cylinder 135 tpi of other 3.5" disks.
>>> Those 40 cylinder 3.5" drives are quite rare.
> Somewhere in my searches I recall reading that the 3 1/2" drives used the same format as the 5 1/4" ones.  Maybe 40 tracks of 16 256 byte sectors.  Oddly, I believe that 2 tracks are "reserved for CP/M" even though it is in ROM and not stored on disk. 
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>> ceramic magnet lost its stuff over time.  When I have time the next
>> project will be a Atmega2650 running
>> a CF to via serial interface.  The drive table can be patched for a
>> larger (up to 8mb) drive.
> I've been planning something very similar for a while, but using an Arduino (ATMega 328) or bare AVR chip and probably a smaller/simpler flash chip.  I din't know about the drive table.  That's interesting.  Would a new ROM have to be burned with the new table?  Do you have an links to the info?

The system in the base PX-8 has a system area for user patches. the
drive table is part of the BIOS and
there are provisions for intercepting the calls to there and patching in
changes or extensions.  Its
detailed in the manuals.


>>> With appropriate format handling software on the PC, it should be
>>> possible for a PC connected using your system to work with actual
>>> Epson diskettes, and emulate the Epson external drives.
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>> There are several software packages on the net to do the fake of the
>> disk via serial and manuals of the system to
>> explain the format.  Likely that software could do the earlier HX20 (and
>> friends) with minor tweaks.
> Here is one I am familiar with that runs on Linux.  Only does drives, AFAIK, no display.
> https://fjkraan.home.xs4all.nl/comp/px4/vfloppy/
Thats true, but the IO on the PX-8 allows for redirection to the serial
port for console and even keyboard.
I've many times used it with my VT320 to save my poor eyes.

> And if anyone is interested here are some more links:
> http://oldcomputer.info/8bit/hx20/index.htm#links
> Navigating through some of those links takes you to the protocol:
> https://fjkraan.home.xs4all.nl/comp/hx20/epsp.html
> Note at the bottom of the page it says the PX-8 and CP/M only use four of the functions.
> This link has lots of HX-20 info.  
> http://electrickery.xs4all.nl/comp/hx20/doc/index.html
> The tms files near the bottom (ch 10-11?) describe the protocol and how it functions in detail.
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> Will
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 Indeed.  its all there.