New Twist on Mobile Pi Access

I just ordered a XMBC MediaPi package from Amazon (MediaPi on Amazon).  I was intrigued by the fact that it is a self contained box with power supply and USB hub powered from a single power supply input - all you do is add the RPi.  This will save loads of time developing my own package to take into work with me.  All of the important ports are available on the outside of the MediaPi package (located at the back).  The input for the SD card has been moved to the front.  This should allow me to work on RPi projects by bringing it into work, having a wi-fi usb adapter to interface to my DIR505L which then can interface via wi-fi to my iPad/bluetooth keyboard combo.  Best of both worlds.  More when it comes in.

Update (from my review):  ... I
originally got this case for the purpose of having a portable Raspberry
Pi (with usb hub). What attracted me to it was the integrated 4 port
hub, mounting for the RPi B, and having all the connections to the back
(SD card to the front). My case was made in India and came in a
Recycled Corrugated box. Designers are in Great Briton. The case fits
handily in a satchel that I carry to work and alleviates me from having
to carry more than one power supply with associated cables and all that
entails. It is obvious that the case was made for the RPi B as a media
case running XBMC/OpenElec, there are no openings for GPIO or camera
cables that you would use if you were in a hobby mode (meaning you would
have to cut your own). Putting the Pi into the case and connecting the
cables took all of 3 minutes. Getting the lid on is a little more of a
challenge but doable. The Pi clips into a slot made for it inside the
case with two tabs and indentations around the edges. There are two
plastic mounds that are threaded for the mounting points on the RPi B
and two screws are included for this purpose. When you get the lid on,
there are two additional screws included for the back to make sure the
lid doesn't come off. Additional niceties include an LED for the front
that indicates when power is applied, an on-off switch on the back so
you are not compelled to unplug the power supply each and every time.
The instructions are adequate to get you going but do not go into any
great detail about orientation of some of the components (like the SD
slot on the front). I noticed this morning that there is a row of red
LEDs that can be seen through the louver on the back, when I shutdown
the RPi these red LEDs went out and seemed to indicate that it was okay
to turn off power (have to verify that one). The only complaint I would
have is that the SD slot on the front seems to be under a lot of
pressure and pushes the case up so that is does not fully join between
bottom and top on the right side front. That is a minor nit. The case
itself is not flimsy, but I wouldn't try storing the largest book you
own on it or throwing it around a lot. It doesn't look half bad sitting
on a table, i.e. I wouldn't feel embarrassed having it in my living
room. I'm kind of cheap so the $60 price tag did throw me off
initially, but the components seem of decent quality. The fact that you
get a "true" current feed coming out of the 4 port usb hub is nice (3
amp power supply, allowing for 0.5 amp for each usb port, plus 0.7 amp
for the RPi, and 0.3 amp remaining for the rest). That is something
that you normally don't get from most over the counter usb hubs (most 7
port usb hubs have a 1-1.5 amp power supply and the usb spec says each
port needs to provide 0.5 amp apiece - you do the math!).

Portable Pi Project - Part #3

Well, I attempted to put the cables together to make the portable RPi.  However, there were several issues that I had to deal with:

(1) when I applied power, it became obvious that there was not enough current going through the wires.  I did check out all of the lines and the voltage was correct.

(2) I found one of the sides of my DPDT switch was momentary.  I needed a switch that was ON-OFF-ON but I picked up one that was ON-OFF-(ON), the (ON) indicating that it was momentary - well, live and learn.

(3) I had the Adafruit 1601 2.8" touch screen on the RPi which added a 100ma load to the power supply, further dragging down the power

(4) the ethernet connection would not light off because of the low power.

So now I am back to trying out the application of power with regular power supplies to make sure that there is not something wrong with the particular RPi that I was using.

After using another, albeit more powerful power supply, I was able to get the RPi to come up and stay up, including the AdaFruit touch screen display. It would appear that I may have misjudged the amount of power needed with the switched setup that I was using earlier.

Portable Pi Project - Part #2

Well work activities, dealing with CEH training and the cert test in two weeks, and other things has prevented me from really stepping up to the plate on the RPi Portable idea.  But to get back to the overall plan on this, I have looked at the power through the system.  The portable looks like the following (not updated from last time):

I have looked at the power lead outs and it looks like a DPDT toggle switch and one 14 position terminal block (I have a 12 position which will have to do) will be able to suit my needs to power everything from either the wall wart or via the battery which is encased with the RPi Portable.  The DPDT will be able to choose the 1.0 amp or 2.1 amp lines from either the wall wart or the battery, and if it has a center off, will be able to act as an on-off switch as well.  What I will need to do is cut up some perfectly good USB cables to make this work.  The cables will end up having a USB plug on one end, and pigtail leads at the other.  I just have to make sure that the data leads are not used in the setup.  So the power circuit should look like the following diagram:

Notice that I have pulled the power out to the board sides for the wall wart. I have also included a power out to the side for charging the battery.  In addition, I have added a board (breadboard) connection so that I can do experiments with this setup as well.  All of the internal connections, except for the DPDT switch can be done with cut USB cables.  It also only requires a 12 position terminal strip.  The high side (2.1 amp connection) goes to the hub and breadboard.  The low side (1.0 amp connection) goes to the RPi and LCD screen.  All grounds are tied together.  Black lines are ground and red lines are 5 volt power lines.

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.