Earlier Atari Hardware Projects
in 1986 I constructed a SIO printer interface based around the National
Semiconductor (who I worked for at the time) INS8048. This is a simple,
old 8 bit microcontroller. The code was held in a 2kbyte EPROM. The device
connected to the centronics parallel interface of a dot-matrix printer.
I still have a printout of the 8048 assembler code. The code to interface
to the SIO bus is remarkably simple. A DIP switch selects whether the Atari
carriage return character is translated to the normal ASCII codes or not.
made this project on the same piece of circuit board as the printer interface.
I had mounted a second SIO connected with the original intention of allowing
the printer interface to be part of a chain, but I never got around to
wiring it up. So in the remaining free circuit board space I used a MAX232
chip to make the SIO to 1050 interface. The intention was to allow me to
read my diskettes and store their images on the PC (and possibly use them
with the Atari emulator). I had a play with the software and I was able
to read Atari diskettes, however a problem was that I didn't know which
density the disks were formatted in.
have used the PIC16C84 in a number of projects. It occurred to me that
it should be possible to interface a PIC to the SIO bus. I interfaced a
16 character LCD display to the PIC. This allowed the commands on the SIO
bus to be displayed. I was interested to see just what special commands
were been sent to my Happy 1050 drive. It wasn't too practical since there
was too much data to display on such a small screen. With the addition
of only an extra TTL chip I am sure that a modern printer interface could
be constructed. If there is enough interest I will post schematics (not
yet drawn) and source code on these web pages.
SIO-2-PIC schematic in PDF format (V1.0)
PIC assembly source code V1.02
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