Touchscreen controller early prototype

["Martyn Wendon" <martynwendon@xxxxxxxxxxx>]

Just because I'm feeling proud that I managed to make something
electronic
that actually works, I thought I'd post to the list about a touchscreen
controller that I'm working on!

I really liked the concept of the Marmitek X10 RF touchscreen controller
mentioned on the list a while ago, but at nearly £200 it was a bit
expensive
and at 10" in size it was a bit big for what I wanted.  Something
around 7"
* 4" would be more appropriate - I was thinking of something that
could be
mounted next to a light switch and not look too monstrous.

So in the spirit of UKHA I set about a homebrew solution.

I already make extensive use of HomeEasy RF equipment with the excellent
RFXCom units and XPLRFX and have a glut of the HE300 remote control units
going to waste, so a quick bit of butchering later and some rudimentary
testing with a multimeter and I saw that it would be fairly easy to
manipulate the inputs of one of these to give up to 34 usable XPL messages
(the HE300 has 16 "switch" on/off commands and a
"group" on/off).

I recently modified an Asus EEE PC with a cheap 7" touchscreen overlay
from
Hong Kong (about £20) and had a spare overlay in the parts bin too and
mimicking the idea of the Marmitek, I wanted to be able to print out a
sheet
of buttons, controls, etc and have the touchscreen on top.

Having a small amount of experience in microcontrollers like arduinos and
PICs I knew that it would be pretty easy to control the HE300 side of
things
with some digital outputs via opto-isolators and suspected that an
appropriate microcontroller should also be able to interface directly to
the
4-wire resistive touchscreen as well (bypassing the USB controller that
came
with it).

After some considerable googling, some rubbish soldering and using far too
many jump-wires, I have a prototype up and running!  At the moment the code
on the arduino simply listens for a "touch" in one half of the
screen to
send an "on" command for one of the HomeEasy switch addresses and
a touch in
the other half of the screen to send an "off" command for the
same address.
Eventually I'll divide the touch area up into zones for each of the 34
possible combinations.

The next prototype will hopefully be mounted in something photo frame
styled
and will move to breadboard & soldered components to reduce the size of
the
electronics.

I've uploaded a rather poor mobile phone video at
http://www.aceshigh.net/touchcontroller.mp4
for anybody that wants to take a
look!


Martyn



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