Commodore PET Projects
When I was trying to find a modern day replacement for my
original PET 8250 disk system, I found that the options were
pretty limited and discovered that, at the time, there seemed to
be two options available :
PETDisk was the first
floppy drive emulator that I found for the PET and
it looked very interesting, I tried to e-mail the
seller a couple of times without success, you may
have more luck, but I then came across petSD.
original petSD -
Designed by Nils Eilers (Obsolete)
In a very similar vein as
is a modern mass storage solution for Commodore PETs
with [an] IEEE-488-bus. It can be used instead of and
alongside vintage floppy disk drives. The petSD
makes file sharing between the PET, the PC and the
The original perSD design is
now obsolete and no longer available, it has been
superseded by petSD+ (see below)
|petSD offered additional
capabilities beyond just floppy disk emulation, the
board could be
fitted with a Real Time Clock, that was fully
supported by the software. Additional components to
provide a USB connection to a PC and a 10MB Ethernet
interface could also be installed, although software
supported for these features was limited.
|Nils did not build petSDs for sale,
until relatively recently, it was available in
ready-built or d-i-y kit form from
German language only website.
to heath issues, Donald, the owner of the site, is
no longer able to produce petSD and it appeared that
I would not be able to find one, other than if one
came up for sale on ebay or the like.
circuit diagram for petSD, along with the parts list
and firmware were available from
Nils' website, so I
wanted to investigate whether I could make my own.
I made contact with Nils, initially with a view to
just making the original petSD available again, but
instead, an updated version has now been developed - see below.
petSD Revisited -
During initial discussions with Nils, he suggested some
changes that could be made to the design which would enhance petSD functionality, but would not have the same cost impact as
petSD-duo design (a
version of petSD).
plan was just to try and build a copy of the original petSD, but,
going further than just suggesting some changes to the original
design, Nils has now taken those changes and produced an
updated version of petSD, that we're calling petSD+.
|Update : 15 April 2015
had completed the design for
and had ordered a prototype PCB for final testing
(All photos courtesy of Nils)
|Schematic of the completed petSD+
|The KiCad 3D model of the board
|Update : 27 April 2015
showing the component and solder sides of the
prototype petSD+ PCB, back from manufacture.
When test fitting the components, Nils identified
a couple of minor issues as described on the
errata link of his updated
The issues are trivial and things were looking
good so far.
|Update : 1 May 2015
first prototype PCB, with the majority of components
|Update : 3 May 2015
Completed prototype - all components are now
mounted, ready for the LCD display.
display mounted on the prototype PCB
|Rear of the display board, wired for
connection to the petSD+ main board.
|Update : 5 May 2015
fitting an almost bare prototype PCB in the case
|Top half of the case mated with the
bottom and a bezel fitted to give a nice tidy
"Photo shopped" mock-up of how petSD+ might look with
the LCD display fitted.
|And the buttons too . . . . . .
Unfortunately though, although the proposed case for
petSD+ was workable, Nils found that the
installation was very tricky and time consuming, so
was not really practical.
Update : 30 May 2015
By now, Nils had created the new firmware for petSD+
and been able to test the basic disk read/write
functions, although the logic for the LCD display
had not been included yet. A future firmware update
would enable the LCD functionality and the boot
loader will be able to reflash the MCU from a binary
file copied to the SD card.
(New releases of firmware are
compatible with all versions of petSD/perSD+.)
Based on his construction and testing experiences
to date, Nils had made a few "tweaks" to the petSD+
design, mainly to correct the minor issues shown in
on his webpage. Once these modifications had been finalised, a new batch of
prototypes was ordered (Board Revision 1.1)
|A photo of my (courtesy of Nils)
It wasn't easy to get a good photo of the
device which also showed the display clearly. In
this photo, a separate photo of the display has been
superimposed for clarity.
The display message means that the firmware
currently does not use the LCD display :-)
Update : 11 June 2015
had finished documenting the
steps required to
assemble one of the petSD+ prototype boards.
Nils provided photos and commentary that he
compiled when assembling the first prototype. The
page is available in both
Update : 1 August 2015
Nils had added the
first LCD functions to the NODISKEMU firmware - a petSD+ hardware diagnostic screen.
See here for the
petSD Availability - 2015 (as
petSD was designed to be constructible by the
average electronics hobbyist, and one of the design
goals was to be able to use through-hole-technology
(THT) components, rather than surface mount chips.
The one exception was the FT232RL USB-serial-adapter
for which a THT equivalent was not available. The
USB - serial adapter has been dropped from the petSD+
design, the only surface mount component remaining
is the SD card reader.
Although my initial interest was driven by my desire to get a petSD for myself, with Nils' permission,
I decided to take on production of a few kits of parts and
manufacturing a few devices to make petSD+ available to anyone else
who might be interested.
Assembly of the petSD+ kit is described on the
I have limited skills with a soldering iron, the surface
mount card readers are rather awkward to work with, so I would
prefer people to buy a kit of parts and assemble petSD+
themselves. However, for anyone not confident in their ability
to build their own, I am prepared to build them for you.
When I asked for input on the prospective supply options, I
had the following responses
Manufacturing & supplying a bare board
Manufacturing & supplying a bare board and the
necessary parts to assemble it
Manufacturing, supplying & assembling a completed
and tested board
Last Update : May 8th 2015
Based on the limited number of responses, supplying a kit of
parts seemed to be the most popular option. I decided that I
make kits available, as well as pre-assembled units for folks who
need one. In practice though, once the kits and pre-assembled
units be case available, the majority of people wanted a
A modified version 2 PCB is currently being designed by Nils,
but this may take a little while to make it into production. In
the meantime, a slightly modified
version "1a" board was produced that corrected the MISO connection issue
described in Nils'
on his web page. (This issue is only relevant to petSD+ boards
that have the ISP port connector fitted which will not be needed
by most users anyway).
Kits of parts and fully assembled petSD+ devices based on the
Version 1.1 PCB are now available for purchase :
Please see the Ordering page for details
Eilers petSD home page
Donald's internet shop
The Vintage Computer Forums