Saturday, March 12, 2011

Kindle Teardown

I went to Best Buy and played with the Kindle in preparation for this project.  The first thing I did was to turn it over and look for screws.  To my horror, there weren't any.  I left empty handed and immediately went to my old friend The Internet.   Approximately 14 seconds after I started my search, I'd discovered two excellent videos showing me exactly how to take the Kindle apart.  Well, I should clarify that...  I knew I wouldn't have a problem taking it apart, the trick would be to make sure it still worked when I put it back together again.

Two site of note here, both are recent favorites of mine.  In no particular order, here they are:

www.eevblog.comThis video was the first I found, and was an excellent tour of the Kindle's guts.  Dave demonstrates exactly how to tear the unit down, and even offers some insight into its construction.  This was an excellent find, and I plan to spend a lot of time here going forward.

My only issue with the EEVBlog video above is that he didn't take the front panel apart to look at the keyboard.  That was the whole reason for this project, so I bookmarked his site and continued my search.  This site is chock full of product reviews and teardown videos, and I quickly found the one I was looking for.  A complete teardown and reassembly video of the 3rd generation Kindle.  He didn't spend much time on the keyboard but he did completely disassemble the unit and spent some additional time on the disassembly procedure (especially as it relates to the screwless case!).  With this information I felt confident that I could completely tear down my Kindle without destroying it. It would be up to me to figure out the keyboard.

It should be noted that this site is not in any way affiliated with the above blogs.  They were an excellent resource for this project however, and I would be remiss if I didn't list them here.  Anyone trying a similar project as mine would find their information incredibly useful.

Enough talk!  Let's void a warranty.

The 3rd-Generation Kindle is a great piece of engineering.  It's much smaller than I expected it to be, and internally it's laid out in a way that allows surprisingly easy maintenance.
This Kindle is at the top of the button transplant list.

I've never used another eReader, so I don't have much to compare it to.  That said, I love it.  My sister loves to read but has trouble holding a book and turning the pages.  This will be exactly what she needs, we just need buttons she can work with!  

When I bought the Kindle the clerk at Best Buy very politely listed my options for extended service plans.  I had to stop myself from laughing out loud.  If only he knew that the first thing I'm going to do is take it home and void the warranty.  Let's get to it!

Challenge accepted.

The first thing you might notice is the fact that the back of the Kindle has no screws.  It's like a big sign saying "I dare you to crack this case open."  What do we say to a challenge like that?  "Watch me."

The case simply snaps together.  All you need to get it apart is a flat bladed screwdriver.  Insert the screwdriver into the seam that runs around the perimeter of the unit, pressing outward.  Once you're able to insert the screwdriver under the rear case, rotate it parallel to the table to pry it apart.  With a little luck this will open the case slightly, and you can move down a bit to the next spot.  Repeat the process all the way around and remove the case.

When the back case comes off, take a moment to look around.  Most notable here is the surprisingly large battery.  It is held in place by two screws, which are easily removed.

Battery screws, begging to be removed.

Once the battery is removed, it's time for the motherboard.  There are two sizes of screws used in the assembly of this device.  Those used to attach the battery are the larger of the two, and there are quite a few more on the frame, the 3G modem and the connector for external lights and such.  

Three screws hold the 3G modem (or in this case a plastic dummy) in place.

The rest of the large frame screws.

Once the silver screws are removed, it's time to get out the magnifying glass and tweezers and start in on the tiny little black screws.  There are 11 of them, and they actively try to hide from you. 

It's like playing "Where's Waldo?", but smaller and more expensive.

 With all the screws removed the motherboard is left floating, but it's not quite time to remove it yet.  There are four ribbon cables connecting all the front panel buttons to the motherboard, along with one miniature four wire cable with a JST-style connector for the speakers.  This connector is at the upper right corner of the image below, just to the right of the dummy 3G modem.  The red and black cable can be removed with a flat bladed screwdriver, or with your fingers (provided yours are smaller than mine!).  Three of the ribbon cables have "zero insertion force" (ZIF) sockets, and can be removed simply by flipping the top door of the connector and easing the cable to the side.  The last ribbon cable (bottom left) uses a different socket, and is a simple press fit.  Lift it straight up to disengage.

Four ribbon cables connect the front panel keys to the motherboard.

Once these have been successfully removed, the motherboard is floating free and can be removed.  Slide it toward the top of the Kindle slightly to free the connectors and switches at the bottom of the case, and lift the entire assembly up and away.  

Motherboard removed.  This is the back of the keypad.

When the motherboard is removed, you can infer the purpose of each ribbon cable removed in the previous step.  the two smaller cables are routed to the side buttons for turning pages.  The large ribbon cable on the lower right is routed to the main keyboard, and the final cable on the lower left handles the eInk controller for the display.

The front panel, from behind.  The display controller cable is clearly visible.

Once the keyboard is removed, the front panel is visible from the rear.  There are a few things to note here.  First, the ghost image on the eInk panel.  This type of display retains whatever was last displayed when power is removed.  Second, the keypad is a simple strip of silicone rubber, with small plungers on the rear of each key.  This type of keypad typically uses strips of conductive rubber on the back of each button to close a connection between two exposed traces on the circuit board underneath.  In this case however, the plungers are not conductive.  The assumption was that we would find pairs of exposed PCB traces to which we could solder wires and hijack each button.  Houston, we might have a problem...

The keyboard itself.

Looking at the keyboard itself, it is clear that we'll need a new approach.  There doesn't seem to be any simple way to connect wires to these buttons and have the user close the circuit by pressing something on the keypad.  

Unless...  This keyboard is connected to the motherboard via a 20-connector ribbon cable visible at the lower left of the image above.  Let's have a look at the connector to which it mates.

Flat ribbon cable connector for the keyboard.

This cable is the only connection between the main keyboard and the motherboard.  The signals from each key must be carried in this cable.  It's a 20-pin connector but I count 42 distinct keys on the front (not counting the four side-mounted buttons for turning pages.  This cable is still our best bet for intercepting the keyboard commands and injecting our own, but it's going to take some tinkering to figure out the signals.

First, let's have a look at the connector.  Flipping through the new Mouser catalog that conveniently arrived yesterday, it looks like this is an FFC (Flexible Flat Cable) connector from Hirose.  The arrow in the picture below confirms that the connector is a 20-position variety.

Closeup of the keyboard connector.

The closest match in the catalog appears to be the 798-FH28E20S05SH05.  

So, what have we learned?  The initial idea of simply soldering wires to the keyboard is out.  It's not feasible with this particular button style so we need a new approach.  We know that the keyboard signals are wired through this connector and cable back to the motherboard, but that cable is far too small and flimsy to solder to directly.  Fortunately it looks like we got lucky with Mouser and just might be able to find a suitable mating connector of our own.  

The next phase will be the creation of a suitable breakout board for that cable.  Once we're able to wire to all 20 signal lines, we can begin hacking the keyboard.  The goal remains the same: substitute our own buttons for the tiny factory keyboard.  

Time to hit to order some connectors. 

1 comment:

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