Camera module as back case (was Re: Slashdotted)

Rask Ingemann Lambertsen rask at
Sat Apr 11 23:42:48 CEST 2009

On Mon, Apr 06, 2009 at 11:41:57AM +0200, Lothar Behrens wrote:
> About the camera issue:
> I have read something about a small computer base case that has a jack  
> or bus system ontop of it's
> case. That way it is extendable with cameras or what ever. I don't  
> know where it was but it was cool.
> Why not think about a back case that includes a cam and using contacts  
> in the inner housing to connect
> the cam to, say an I2C bus or even an USB hub (USB2)?

   But how will you get the image pixels across to the Neo? There has been
some discussion about this on the hardware list, starting with the message
"Weird hardware mod ???" back in January. To sum it up:

1) USB. There are many USB webcams available, but the difficulty is finding
one that works well on a USB 1.1 bus, because USB 2.0 is fast enough that
the cameras can simply dump the image across the cable with little or no
buffering in the camera. So most cameras won't have enough buffer space to
hold a good still image, and for the same reason also don't have the
buffer space needed for any of the good video compression codecs.

2) A generic image sensor interface with I2C for control and 8-bit parallel
port for data transfer. Example camera chip:

The options:

  2a) The Glamo has an unused camera interface, even with all the important
  pins connected to a resistor network, but the documentation is under NDA.

  2b) Roll your own somehow. The SC32442B has lots of unused GPIO - e.g.
  most of the LCD interface - but the ones that appear to be connected to
  somewhere accessible are scattered all over the place in register space.

<rant index=1>
It would have been a lot easier if the SC32442B camera interface pins hadn't
been frittered away for GPIO assignments that could just as well have been
served by the pins of the unused LCD interface instead. Even if you don't
want to use them for a camera, the 13 of them are nicely lumped together in
GPIO port J. They would have been fine for many projects.

<rant index=2>
Of the only two external DMA request pins, one is a dead end and the
other one is connected to the GPS as a simple output. Again lots of other
less valuable GPIO pins are available for such purposes.

Rask Ingemann Lambertsen
Danish law requires addresses in e-mail to be logged and stored for a year

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