this is the 40h logic board. you will be mostly concerned with the two double rows of pins shown here:

everything from left to right, from the above perspective:

left header, top row: led column (Y, DIGIT) 0-7
left header, bottom row: button column (Y, SELECT) 0-7
right header, top row: led row (X, SEGMENT) 0-7
right header, bottom row: button row (X, INPUT) 0-7

the button and led systems create two discrete 8×8 grids. at each grid intersection (64 points per grid) is either an LED or a button in series with a diode.

for the LED, the anode (long lead) is towards the DIGIT side.

for the button, use a general purpose diode (1N4148 or similar), anode towards the SELECT side. see the bottom of this page for a really lo-fi wiring diagram.

if you want to know why we use the diode, see here: http://www.dribin.org/dave/keyboard/one_html/

(the short version, is that it allows complete discrete detection of each button’s state (as opposed to a computer keyboard, which can’t.)

we’ll post diagrams soon enough.

simple testing

to do a simple test, hook up some ribbon cables to the board (headers on both sides).

connect an led between two places on the top rows of the headers, long lead on the left.

open up _serial_howto.mxb from the base package.

click the box down at the bottom which is labeled /led/test (this will turn on all LEDs). toggle it, it should toggle the led.

put a wire in one point on the bottom row or either header, then touch the other part of the wire to the bottom row of the other header. you should see a little red dot on the matrix towards the bottom of the screen. it’s detecting button pressed.

now it’s time to go read more on the serial protocol.

here’s how you wire one button on the matrix. just build it out.

lots of people are considering using the sparkfun pads. they’re pretty nice, but understand that they’re really really big.

here’s a comparison image:

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simple testing