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Commodore_Free_Issue_13_2007_Commodore_Computer_Club.d64
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t.1541 iii proj
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2023-02-26
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uProject: 1541-III
http://jderogee.tripod.com/
project1541.htm
How it all started:
I wanted some extra hardware to fit the
big 'hole' inside my SX64. That hole
was created by the previous owner who
liked some additional buttons (reset,
device selection etc.) & replaced the
complete disk storage compartment for
an ugly glued on front plate.
Also the extra hardware I would like to
build must be compatible with my other
CBM machines (C16 & VIC20) & the usage
of .D64 files seemed like an obvious
choice. Therefore an IEC based device
with standard DOS commands. So no extra
software or cartridges & D64 files can
be found all over the internet...
Strangely at that point in time this
did not exist. So I decided to build it
myself, from scratch.
Therefore I had to learn the IEC-bus
principles & low level command
structures & since these docs are rare,
I had to build my own (PC-based,
LPT-port, VisualBasic6.0) logic
analyser first.
Also how files are stored on a
MMC/SD-card, how to access these files,
how to interpret .D64 files, how to
interpret real IEC-bus commands etc...
Fortunately the FAT16 code could be
reused from another project.
Having only one or two hours each day,
it took me a year to come this far. But
I like the results & what it can do,
I'm very proud of it & this is only the
beginning.
Allmost 1.5 years after the initial
start of the project, I finally managed
to build the 1541-III inside my SX-64 &
although it looks VERY retro (with
those big switches & large red reset
button), Im pleased with the result.
Mostly because it helps me to keep a
tidy workspace & I can take it with me
whenever I want to show the project. A
happy end after all...
Project: 1541-III
This project got a lot of attention at
the Commodore show 18 FEB 2006. The
prototype is built inside an old mouse
joystick switchbox. It made me realize
that the 1541-III project is very
interesting for other C= fans as well.
Therefore the project has been
transformed into an already assembled
kit.
For those who are interested, read the
how it all started. The prototype holds
a 2 line character LCD, but during
further development of this project it
quickly became clear that a 2 line char
LCD could not hold all the relevant
info in a convenient way. Therefore the
Nokia 3310 display (PCD8544, cheap,
small, graphical, 84x48pixels)
completely replaced the character LCD
in this project. The final design
changes have resulted in a version
smaller & easier to construct.
What it does:
The 1541-III is a PIC microcontroller
controlling an FAT16 MMC/SD card with
.D64 files. It is connected to the
C= via a standard IEC bus. The circuit
as a whole behaves like a 1541 drive
(therefore the name 1541-III). The
MMC/SD card contains D64-files (or
normal .PRG files). The user can select
one .D64 file with standard
LOAD"$",DEVICE commands. Once a .D64
file is selected it can be accessed
like it was a real 5 1/4" floppy. The
nice thing of this solution is that you
can download D64-files from internet to
your MMC/SD card without the need of
extra tools or cables
Because the 1541-III doesn't need to be
inserted into the expansion port or
require additional software or kernel
it will work on every C= computer (&
even the hacked C64 DTV) that has an
IEC-bus. It has been successfully
tested on the following machines: VIC
20, C64, C16 & +4 since the C64 is the
most common 8-bit IEC machine this page
will be written out of the C64
perspective.
Because the circuit is based on a PIC
microcontroller & not a fancy FPGA or
65xx processor it will never act 100%
the same as an 1541. This is the main
reason why fastloaders will not work as
on a real 1541. Still it is an
affordable alternative for using .D64
files on a real commodore computer.
Because things can always be better...
the 1541-III is capable of upgrading
its firmware (using an PC with
HyperTerminal & RS232 port). AND...
since the firmware (programmed in C) of
the 1541-III is released as open source
software, everybody can develop new
features. Or otherwise download the
latest version of the firmware from
the website
For developers & hackers...
The main idea behind this project is
open source. Giving away the source
code development on IEC based devices
is encouraged. The hardware of the
1541-III is set up in such a way that
it can be re-used for other
applications other then the 1541-III
itself. For instance the PIC has
several unused pins that can be used as
ADC or I/O so an oscilloscope or
digital voltmeter for your C64 can be
built. Or it can be the base of an
IEC-based network drive so you can
connect your CBM computer to a network.
And instead of a disk you'd access
files on your network. But (off course)
this all would require some serious
firmware development.
A more interesting side project that
can achieve a near 100% compatibility
is using the 1541-III electronics as a
replacement of the real 1541-drive
mechanics. Mimicing the GCR datastream
& keeping the 65xx of the real 1541 the
ultimate upgrade would be within reach.
The 1541-III PCB is already prepared
for this task but requires some extra
serious firmware development (&
soldering skills for making the
required connections inside your 1541)
Current features:
Some pictures of the information that
can be shown on the 1541-IIIs LCD.
Loading flimbos quest
Required power supply:
The best option would be a datasette
connector to interface to the cassette
port, but since this connector is
difficult to obtain an alternative
would be drawing power from the
cartridge port, this way a connector
can be made from PCB material only. And
since the 1541-III is not (yet)
compatible with most cartridges (final
cart, power cart, etc.) this should not
be a problem. For those who wish to
keep the cartridge-port free they have
to sacrifice a datasette in order to
get the connector. Down below is an
overview of option to steal power from
your precious C64
Finally, for everyone who doesnt like
to draw power from their precious
computer an alternative is allways an
additional stabilized 5V DC supply