Speak and Spell – Keyboard Matrix

Tonight i spent some time at HAC:Manchester reverse engineering the keyboard matrix on our speak and spell, in preparation for hooking it up to an MBED.  Since nobody else has released this information (as far as i can tell), here is the pinout:

pin 3 4 5 6 7 8 9 10
1 u k off a f ? p z
2 v l go b g & q `
11 w m <- c h ??? r #
12 x n d i :) s /
13 y o _ e j on t return

This means that when the ‘off’ button is pressed, for example, pin 1 and pin 5 will be connected together.

To read a matrix keyboard like this, we write some code that steps through the ‘down’ set of pins (1, 2, 11, 12, 13), holding them low one at a time, then checks each of the other pins (3-10) to see if anything is being held low. If so, we perform a lookup on the table above.

Code to follow next week!