Commodore Free 5/Commodore_Free_Issue_05_2007_Commodore_Computer_Club.d64/t.dtv hack

Text File | 2023-02-26 | 7KB | 218 lines

uDTV Hacking

Here are a few pics of my own DTV
Hummer project. I had an old PSOne LCD
screen lying around and I thought I'd
make a C64 laptop. Actually, it's more
like a C64 PDA! It measures 6.5 x 6 x
1.5 inches (15.5 x 16.5 x 4 cm) when
closed. It can run from an AC wall
adapter or 6 NiMH AA batteries. The
keyboard is hacked from a portable
folding keyboard for a Jornada PDA
which outputs RS-232. I'm using a PIC
16F88 to decode the signals and
reencode them to PS/2 (that was an
ordeal to figure out).

The PIC checks to see if an external
PS/2 keyboard is connected on power
up. If one is hooked up, it will route
data from that instead. There is an
internal ampilfied speaker as well as
connections for audio and video output
on the back.

There's a serial connection for a disk
drive and an SD card slot in the side
for a 1541-III but I haven't been able
to get that to work yet. I also have a
connection for a userport/joystick.
The joystick in the picture is a
hacked Atari keychain joystick. The
mini joystick wasn't in the original
plan but after I accidentally
discovered it on ebay, it seemed
perfect. Here's a how-to post
regarding the RS232 to PS/2 keyboard
hack:

http://jledger.proboards19.com/index.c
gi?board=dtvh
acking&action=display&thread=116778302
4

The Micro Folding Keyboard (Model#:
TKB420HP) made by Micro Innovations is
a small portable keyboard for
attaching to a Jornada PDA. It
basically has all keys needed for
adapting to a DTV but unfortunately
outputs RS-232 instead of PS/2. The
following information describes how to
interface this keyboard to DTV Hummer
and possible the rest of the DTV
versions. Out of the box:
Disassembling the keyboard, you'll see
5 labeled connections: VCC, RTS, RXD,
DCD, and GND. VCC is +5V for this
unit. RXD is the line on which data is
actually sent, although the keyboard
won't send anything until RTS is
pulled high. I do this right on the
board by soldering a 1k resistor
between the RTS pad and the onboard
microcontroller's Vcc pad (see
picture). By doing this, you only need
to run three wires from the keyboard
(VCC, RXD and Ground).

As far as what mechanical
modificationsE I chose to cut away a
lot of extra plastic from the two
folding halves and superglue the sides
together. This effectively created one
solid piece. I also glued the
flexi-ribbon flat against itself to
take up less space.

Since this keyboard outputs RS-232
(9600 baud, 8 data bits, 1 stop bit
and no-parity), a PIC 16F88
microcontroller is used to convert the
data to PS/2 for the DTV. PS/2
keyboards use "make" and "break" codes

One or more "make" codes is sent when
a key is pressed and several "break"
codes and are sent on key release. The
Jornada keyboard kind of works the
same way in that it uses make and
break codes, unfortunately the codes
are not a one for one match and must
be re-mapped by the PIC.

On power up, the PIC will check to see
if a regular external PS/2 is
attached. If so, it will just go into
"repeater" mode and pass along any
signals from the PS/2 keyboard to the
DTV. The PIC adds a one second delay
to get rid of the pesky "V". Here's
the circuit:

The diode and resistor on pin 4 are
for in-circuit serial programming
(ICSP) and can be left out as well as
any other connections labeled ICSP.
The 100k resistor on pin 11 is needed
even if you decide not to mess with
the external PS/2 connector, so don't
leave it out. The rest is fairly
straight forward. The 100uF cap may
need to be larger depending on your
setup. 100uF worked initially for me
until I added an LCD screen to my
design. The power surge on start up
was too much and the keyboard would
not initialize properly until I
increased it to 470uF. For timing, the
internal 8 MHz oscillator is used. It
seems to work just fine.

Here's the HEX file:
www.picobay.com/picodore64/JornadaKBD1
6F88.he x

And the source code:
www.picobay.com/picodore64/JornadaKBD1
6F88.txt

Again, this is for a 16F88 and any $15
JDM PIC programmer will work just
fine. The source code is written in
PicBasic Pro. The code could probably
be reduced to half the size by
constructing the send codes on the fly
instead of hard coding them. The
start, stop parity bit could be added
automatically and each make/break code
would only take up a byte instead of a
word. But the 16F88 has 4K of space
and I wasn't tight on space. Maybe as
I add more features, I'll recode that
section. And while I'm at it, I'll
switch to using interrupts to get the
data from the Jornada keyboard instead
of just waiting for data. Obviously
this is an adapted keyboard and I had
to switch some of the key assignments:
Today = ESC (RUNSTOP) Space = INSERT
Windows key = Commodore Key FN + Right
Arrow = HOME FN + CRTL + Right Arrow =
CLR SCN The 4 keys in the top left are
the F1 thru F4 keys, F5 thru F8 with
the FN pressed. I didn't bother to
implement the Numlock keypad, there
didn't seem to be much point to doing
so. Just for the heck of it I'm
posting the PS/2 waveform of a make
code for the "A" key. Channel 1 is the
clock and Channel 2 is data. This is
from a real PS/2 keyboard.

Here are the specs: Mainboard: Hummer
DTV Construction: Hobby plywood
covered in faux stainless steel
contact paper Size: 6.5" x 6" x 1.5"
(closed) Power: 7.5v wall adapter or 6
rechargable AA NiMH batteries

Screen: 5" LCD Keyboard: 69-key QWERTY
Sound: Ampilfied 1.5" 0.4W internal
speaker Connections: power,
userport/joystick, serial disk drive,
audio/video output, headphone jack,
external PS/2 keyboard, SD card slot.
Addition peripherals: 1.75" x 1.5"
mini Atari joystick.

Features: on screen display for volume
and brightness control, auto sensing
of external keyboard connection,
programmable funtion keys, video
selector switch. Although I plan on
posting a more length write-up, for
now, I'll give you just the important
details: The LCD screen is from a
PSOne. I'm also using on LCD's board
audio amp to drive the speaker. The
LCD is what ultimately drove my power
requirements. Almost the entire
circuit for the LCD uses 5v except for
one IC which needs between 7v and 8v
to generate H-Sync.

The keyboard was a bitch to figure out
and will be the subject of a post of
it's own. It's from a Jornada foldaway
keyboard made by Micro Innovations. In
terms of construction, I had cut away
a lot of extra plastic and superglue
the two halves together making a
single solid keyboard.

The keyboard normally interfaces with
a HP Jornada via a RS-232 link and
special driver. I was able to capture
all the output codes and program a
16F88 PIC microcontroller to re-map
and output with the appropriate PS/2
protocol. On power up, the PIC checks
if there is an extrenal keyboard
attached. If so, it ignores data from
the onboard keyboard.


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