BSD UNIX minicomputer
Well, after a bit playing with retrobsd
project I decided to build another useless machine. It was fairly
simple - the whle device consists of three parts - main board, terminal
and keyboard.
Motherboard
I used main board I designed
last year for retrobsd project. I didn't want to spend RAM and
execution speed for keyboard and display drivers, that's why I
connected terminal and keyboard to tty0 device. What more, I have no
experience in writing UNIX drivers.
There is probably not much to be said about the mainboard - more info is at retrobsd project page.
Terminal
I took code from Matthew Sarnoff
and adapted it to my device. It is rather messy, so you better don't
look at the sources. The original bits from Matthew are the commented
ones. My code is uncommented.
I
used dsPIC33FJ128GP802 just because I had it on hand, no special
reasons for using this MCU. Many of PIC24 devices should work too with
small to no changes. I'll do it in future, as this dsPIC has higher
current than I would accept.
LCD is RX240128A,
resolution 240x128 gives 60x16 characters in 8x4 matrix. The terminal
works at 115200 baud and currently there is no backlight manipulation, though there is transistor ready to do this.
Keyboard
That
was quite easy - I wrote this simple code in PIC16 assembly (just
because I wanted to do it in assembly) in one evening. It runs on
PIC16F873A, but it should work on virtually any PIC16 in 28 pin package
with USART. Debouncing is
poor, it is subject of future improvement. There is nothing special
about it - just keys matrix and PIC, I don't even have schematics of
it. If you are capable of building this, you should be able to guess
hardware connections from source files.
Keys come from old 8-bit czecho-slovak computer from 80's era, PMD-85. I had one piece in very bad condition, so after long resuscitation it served as organ donor for repairing other PMD's.
Whole
device draws about 100-150mA, depending on tasks it executes. I'm
planning to bring consumption few times lower to allow longer play-time
on small Li-Ion cells.
Video at youtube
Link to picassa album
Package containing display sources, PCB artwork and keyboard sources
For more question, fell free to ask me via e-mail or so.
Updated 20.02.2013
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