

The Laser Doodler - daeken
http://ch00ftech.com/2012/07/26/the-laser-doodler/

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frankus
I once had a co-worker whose side project was a little wireless weather
station transmitter (back in the late 90s). He was getting reports of the
batteries draining in a matter o days, when in testing (and in theory) they
should last months.

After a lot of head scratching he discovered that the bit-change operation on
the I/O port of the chip he was using was doing a read-modify-write routine.
One of the pins on the I/O port (intended to be "write-only") was attached to
a status LED.

In bright sunlight, the status LED was generating enough power to read high on
the I/O port, so any unrelated bit flips on the port could cause the LED to
turn and remain on in bright sunlight.

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tlrobinson
Jeff Han demonstrated this concept a few years ago, but without the laser:
<http://cs.nyu.edu/~jhan/ledtouch/index.html>

I tried to wire one up myself but couldn't get it to work. I think certain LED
matrixes don't work as well (maybe translucent vs transparent LEDs)

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stcredzero
I wonder if one could combine a webcam and a projector for a "doodling"
application? The rectangle of the bright white screen could be used for
calibration. The software would look for a particular shade of red or green
within that rectangle, and re-project at that spot.

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ChuckMcM
Heh, I've got exactly this app sort of half working on my Pandaboard. I've
been fighting the gstreamer API a bit in a non-X11 config.

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samstave
Do you have more info? I have some architects (the physical building type) I
am working with whom are very interested in such applications.

Can you show me what it is you have/are doing?

~~~
ChuckMcM
It's my intention to post it to Github, I've been going back and forth with
the Texas Instruments folks on the Pandaboard group to figure out the best way
to do graphics without X (and DirectFB wasn't working out for me, Wayland
would rock but its not there yet). Assuming my experiments with that are
successful I'll get the drawing side of things up sooner, then work the camera
side.

Note that the only reason its taking me this long is because I'm trying to be
cheap cheap cheap. You can do this with a laptop running OCV connected to a
projector pretty easily. (although the first time you try this like I did, the
feedback is really really trippy :-)

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blhack
This is really cool, and ch00f does quite a few cool projects that pop up on
reddit all the time.

~~~
daeken
Yeah, that's how I found his work. Saw a post of his on /r/cableporn last
night and ended up going through a bunch of his blog.

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jeffbarr
Very clever!

