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Saturday, September 21, 2013

Portable Pi Project - Part #1

Well I now have some challenges ahead of me. I have decided that I need to make a portable RPi layout for testing. The idea is to bring it in to work to have around during lunchtime, when I get a chance to eat a bowl of soup. I figure if I put an RPi, hub, battery, various USB devices, external wifi adapters, the RPi camera, etc. on a sheet of Lexan I can make good use of it. This will allow me to code and test out some projects while being able to put the RPi into my bag in the morning.
I think that putting the equipment between two sheets of Lexan, with enough standoffs, I should be far enough along. The real problem is the orientation of the peripheral ports. I need to get to the USB, Ethernet, HDMI, SD card slot and maybe the GPIO from the side of the setup. The SD card slot is needed to change out different experiment setups. The others are self explanatory.
If I get it tied down enough with a sufficiently narrow width, it should work.
Update:  I purchased two 8x10 sheets of Lexan from my local Home Depot, along with 6 - 1" plastic standoffs, 4 rubber feet, and mounting hardware.  I wasn't able to find M3 screws or nuts but I did have some that I purchased at a different time.  It turns out that 6-32 will not fit into the mounting holes of the RPi, but M3 will.  I was able to take 1/2" standoffs and cut them in half with a PVC pipe cutter (does a really good job BTW). I mounted the RPi in one corner with the power and SD card slot about 1/4" from the edge; this has the SD card sticking out when it is mounted, but makes it easy to change out.  I wanted to be able to get to the SD card slot for changing the peripheral.  Now my issue is mounting of the other elements.  I figure that I should take apart the USB hub and that should make it easier to mount in the shell.  The current state of the configuration is shown in the following picture.






I am planning on mounting the USB Hub in the center of the left side in the photo (the case for the USB Hub has been removed). The battery will be mounted on the bottom.  I will also mount a USB-WiFi adapter with antenna at the top.  In addition, I will probably mount either an Arduino and/or a USB-Audio adapter on the left.  That should cover me for most applications.  I would assume that I would attach the Logitech keyboard USB dongle on the right side of the USB Hub.

Mounting for the battery and other components has been somewhat of an issue. I would like to be able to remove the battery at times since I also use it with a robot and it also acts as an emergency iPhone battery recharger. I would like to get a clamp type mechanism but I am not sure where I would find such an animal or what it even looks like. Looks like a trip to Home Depot / Loews is in order here.

Monday, September 9, 2013

Finally got around to installing the RPi Camera

This weekend was pretty much a blur. I did manage to plug in one of the two cameras that I had bought for the RPi back a couple of months. I just followed the instructions that came with the cameras (remove tape from header next to the Ethernet port, pull up on both sides of the locking mechanism gently, insert the camera flexible cable so that the shiny part of the cable faces away from the Ethernet port, after ensuring the cable is all the way in, push down on the header lock). I then tried out the instructions found at http://www.raspberrypi.org/camera to test. Picture of the camera is below:





Friday, September 6, 2013

Reworking Some Ideas on the RGB LED Cube

I have not been working on the LED Cube for a while.  Now that I am back to thinking about it, I want to redefine the interfaces from the Raspberry Pi.  I was thinking that a good way of doing this would be to interface to the LED Cube through an Arduino.  I could re-purpose an Arduino to be an I2C device coming in with additional I2C busses going out.  The repetitive nature of flashing the LEDs is ideal for the Arduino.  I could have the RPi formulate the 3D nature of the data points at each phase and have the Arduino take care of displaying the 3D points in the LED Cube.  So the RPi would calculate what should be displayed, relay that to the Arduino, tell the Arduino to start displaying the new 3D point set, and while the Arduino switches to the new data set, the RPi would be busy calculating a different 3D point set.  The nature of our eyesight is that we need to have things change at roughly 1/24 of a second (frame rate) to visualize motion.  That should be easily attainable with the Arduino.  The RPi is better suited to gather other pieces of information.