The Electronics part 2
The LED display could easily have been
simulated on the top display, but I thought that
would detract from the originality of the game. I
have always been a fan of 7 segment numeric
displays so leaving it off was not an option.
While the sounds produced by the original
Tower are basically old school microcontroller
Pulse Width Modulated audio, they are quite
distinctive and add to the retro experience. In
testing I was able to reproduce the musical
scores but the other sound effects would take a
long time staring at an oscilloscope and tapping
on a keyboard trying to program what I would
see, this would also require a working tower that I
didn't have. Luckily the sound samples are
available for downloading on the internet. I would
need a sound module. I selected the SOMO-14D
sound module and converted the samples to AD4
format, added an 8ohm .25 watt speaker and was
very happy with the result.
I used the same style 3x4 matrix 12 key
membrane keypad that I used to fix the keypad in
the original tower.
I added up how many inputs and outputs I
would need and estimated that I would need
roughly 16K of flash ram for the programming. I
chose the Pic 18F452. It can run at 40mhz, has
32K of flash, more than enough I/O, and I got it for
less than $5.
The Circuit Board:
I have made quite a few circuit boards at home
but I decided this would be a great project to have
my first professional board made. The final lay out
and size of the board would of course depend on
the tower I would build. So after bread boarding
all of my test circuits, I sat down and fired up
Eagle Cad to build the schematic.