NP-41 Emulator (may be)

[Chris Chung]

(03-09-2016 03:35 PM)Harald Wrote:  Hi Chris,

thanks for the info!
I think the build will be easy with those instructions.
However, I didn't quite understand how your key scanning works

(03-09-2016 01:49 PM)Chris Chung Wrote:  ...
Instead, I scan my 10 pins like so.

pin 0 scans w/ 1 2 3 4 5 6 7 8 9
pin 1 scans w/ 2 3 4 5 6 7 8 9
pin 2 scans w/ 3 4 5 6 7 8 9
pin 3 scans w/ 4 5 6 7 8 9
....

Do you have a schematic for the keyboard? That might help me understand what you are doing.

Cheers,
Harald

I did not properly draw a schematic, I just used Fritzing to "draw" the PCB using it's manual trace routing.

Here is a simplified schematic for a 5 pin key multiplexer to illustrate the connection and scanning, it yields 4 + 3 + 2 + 1 keys.

   

In the firmware I start by placing pin 0 (say from top) as output set to high, pin 1, 2, 3, 4 as input w/ pull-down to low. And I would scan for the 4 input pins to see any of the 1st row keys has been hit.

On the next scan cycle I would place pin 1 as output to high, and scan for pin 2, 3, and 4. I won't scan pin 0 here as it was done in the last scan cycle.

Likewise on the next can cycle we can the next row w/ one fewer inputs / buttons.