Friday, March 18, 2011

Christmas in March!

It's always a good week when you get packages from both Mouser and SparkFun in the space of two days.  My Hirose connectors and ribbon cables arrived, along with a breakout board from SparkFun.

Remember the goal of this project, to create a custom keyboard for use with a standard Kindle.  The Kindle is a fantastic design, but only if you have small fingers or superior motor control.  For people with certain physical disabilities, this device is completely unusable.

Today we'll begin creating the physical adapter board that will allow us to solder buttons and such together to create a custom keyboard.  We'll worry about the actual layout and physical appearance later.  First we have to prove that this is even possible.  The first task is to gain access to each of the tiny conductors in the Flexible Flat Cable (FFC) on the Kindle motherboard.

The Hirose connector used on the Kindle is a 20-pin type, with 0.5mm pin spacing.  The only breakout I could find readily available is an 80-pin TQFP type, for use with certain microcontrollers.  It's a great design, with duplicate pads on both sides.  There are four possible mounting locations for a connector of this type on each side of the board, which means I can screw up the soldering 7 times and still not be out of luck.

I really only need one connector.  I bought six.  Turns out three was the magic number (surface mount soldering is tricky!).

Thanks to the surprisingly handy magnifying ring lamp my Dad got me back in college, I was finally able to secure the connector to the breakout without shorting any of the leads.  A quick continuity test with my multimeter showed that each pin was securely fastened to the board.

A couple scorch marks never hurt anyone...

Flat Flexible Cable (FFC) test fit

Now that we've got the connector attached to a suitable (albeit oddly shaped) breakout board, let's do one final sanity check.  We need to make sure the other end of the cable actually fits into the Kindle's socket.  This is the acid test, and will prove whether or not we actually bought the right connector.

It fits!

Whew!  That's a relief.  The cable fits securely into both the Kindle connector and my hacked-together breakout board.

That's enough for today.  Now that we have access to the keyboard, we can begin testing to figure out exactly how the buttons work.

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