Tuesday, March 29, 2016

HotKey 2

The day after the proof of concept

I'm using my Hotkey device now since some days and it is pretty practical for the daily workflow. So I've decided to make a more clean or professional version of the HotKey device.

The surprise

I've ordered one of these external USB number pads for notebooks just to have a look inside if there would be enough space to replace the electronics and maybe reuse the keypad matrix. 

JACKPOT! After I have opened it I figured out that there is plenty of space for my upcoming PCB design and also the Keypad Matrix is not glued to the PCB its connected by a flat flex connector, so that it could be reused completely.

Some reverse engineering 

A closer look to the area above the connector of the keypad shows us that the designer of the PCB was so kind to add some labelled test points for me.

This gave me the ability to quickly figure out which button triggers which row and column.

Ordered by key:
7C1 R28C2 R29C3 R2"-"C2 R1
4C1 R35C2 R36C3 R3"+"C4 R3
1C1 R42C2 R43C3 R4
C4 R4
0C1 R500C2 R5.C4 R5

Ordered by column and row:
C1 R1NUMC2 R1-C3 R1*C4 R1/C5 R1
C1 R27C2 R28C3 R29C4 R2BCKSPCC5 R2
C1 R34C2 R35C3 R36C4 R3+C5 R3
C1 R41C2 R42C3 R43C4 R4ENTERC5 R4TAB
C1 R50C2 R500C3 R5C4 R5.C5 R5

Then it was quite easy to also figure out the pin out of the connector:


What's Next?

The next step would be to wire up the keypad matrix to the Arduino Leonardo and figure out a proper algorithm to read the key presses from the matrix.