MPR121 touch sensor IC with matrix

hello
I've got a MPR121 Capacitive Touch Sensor chip, made by Freescale.
It has 12 touch input channels and works on I2C. I haven't had problems in making it work and reading its 12 inputs.
On the Freescale website I've read that it is possible to make a 5x7 button matrix using only 1 chip, but it does not say how.
How can this be done? Would it work the same way "standard mechanical button matrixs" work?

It would be great if your share the picture so it would get easy for us to understand.

Check out this screenshot from Freescale application note AN4600, page 3.

You make a matrix of 7 tiles on one axis and 5 in the other then location is determined by which sensors are active, e.g. if 0 & 7 are active the user is pressing in the upper-left corner, if 3 & 9 are active it’s a middle press, etc.

Good luck!

ok I understand, many thanks :slight_smile:
I believe this will only work using a double side pcb or something that let you place 2 sensors one on the top of the other but insulated from each other

Dimitree:
ok I understand, many thanks :slight_smile:
I believe this will only work using a double side pcb or something that let you place 2 sensors one on the top of the other but insulated from each other

100% correct. The traces have to be physically isolated from each other or the capacitance from one will bleed into the other.