External programmable I2C QWERTY keypad matrix controller chip for $1

[philpirj]

http://www.analog.com/en/products/inter ... t-overview

Main application as I see it is to offload matrix scanning from the main controller chip, thus reducing its firmware complexity, performance requirements and the number of pins to a bare minimum (to, say a ATmega8U2).

Key features:
- Keypad decoding for matrix up to 11 x 8
- Key press/release interrupts
- Key pad lock/unlock
- GPIO functions
- I2C interface with Fast-mode plus (Fm+) support up to 1 Mbps

It has some younger brothers with less GPIO:
http://www.analog.com/en/products/inter ... t-overview
http://www.analog.com/en/products/inter ... t-overview
http://www.analog.com/en/products/inter ... t-overview

It's not clear however if it's capable of NKRO, and if there us a cheap breakout board for it.

[Engicoder]

These types of chips have been around for decades, the problem is that they are generally hard to find in stock in small quantities and/or they come in packages that are not friendly to hobbyists. When you do find them they cost as much as an equivalent micro that can do the same job as well as interface with the computer. Using one of these would also require a basic micro to interface with the computer, so you have to buy and solder two chips instead of one.