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• Blowing up the apple

  jimmy.c.alzen • 08/20/2014 at 10:37 • 0 comments

  Here is a higher resolution version of the apple picture from the video:

• New focus screen is ready

  jimmy.c.alzen • 08/18/2014 at 08:00 • 0 comments

  The new focus screen is hinged in the bottom and a lot more solid than my earlier attempt. 

  Also it is adjustable, something I found out is necessary. The tolerance needed to get a good focus is a lot less than 1mm.

• WiFi module

  jimmy.c.alzen • 07/20/2014 at 13:58 • 0 comments

  Success! WiFi module is working and connects to AP!

  Running all three external devices on the same SPI bus caused some trouble. After a lot of debugging I found out that the CC3000 and the ILI9340 TFT uses different SPI modes, plus the CC3000 library uses an SPI interrupt. The quick-and-dirty fix was to add this to each driver function in Adafruit_ILI9340.cpp:

  noInterrupts();

  SPI.setDataMode(SPI_MODE0);

    // function code

  SPI.setDataMode(SPI_MODE1);

  interrupts();

  The elegant fix would be to take advantage of the SAM3X's enhanced SPI capabilities to select the correct mode and speed automatically when accessing different devices on the same bus, but then I would have to rewrite all three libraries.

• Further developments

  jimmy.c.alzen • 07/08/2014 at 18:26 • 0 comments

  Two main things are in the pipeline right now: 

  1) Replace focus screen. The old one is way too flimsy. The new one will be made of glass. I have sanded a suitable glass plate, now it's just a matter of mounting it.

  2) It would be nice with a larger display. That way I can see immediately if the picture is going to be any good and save time by cancelling it if it is not. I think WiFi+Android is the way to go here. I have ordered a CC3000 breakout board. Also I get to learn writing Android apps, something I wanted to try for a long time now. Maybe I can also get rid of the awful maximum latency on sd cards by storing the pictures on the phone (and letting Android buffer the data in RAM). Most writes takes milliseconds but once in a while it takes .5 seconds. That really is not acceptable when photographing something moving.

• Apertures

  jimmy.c.alzen • 07/04/2014 at 16:09 • 0 comments

  So the camera is more or less finished. After using for a week or two I find I really miss a manual aperture stop. When using a 140mm F/3.2 from an old dia projector I can't set the shutter fast enough to avoid overexposing the images in daylight. This is because the Due can't A/D convert faster than about 300k samples/second without really complicating the code. 

  So this is what I came up with:

  Why limit yourself to round holes when you can have some fancy shapes instead? Now I just have to find a way to make it quick and easy to change aperture stops.

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