Keypad

How to connect a keypad to your Armadeus board

Introduction

Your Armadeus board allows you to connect a (matrix or not) keypad as input device. Keypads are a collection of switches assembled together to emulate a kind of keyboard to ease user interaction with your system.

Solutions

There are several solutions to connect a keypad to your Armadeus board:

Keypad directly connected to i.MXL/27

One GPIO for one key

This type of keypad generally called "common ground keypad" is the easiest one to build: connect your switch to an i.MX GPIO (with a pullup) on one side and to the ground on the other side . If you need more than 6 keys, this construction is however "GPIO consuming" and you would better use matrix keypads.
Under Test...

Matrix keypads on i.MX27

The i.MX27 has an internal controller that can drive 8x8 keypads (= 64 keys with 16 dedicated pins): Keypad usage on i.MX27. Please consult the i.MX27 Reference Manual (Chapter 25) for more informations.

Matrix keypads on i.MXL

Driver for i.MX GPIO controlled keypads

By default your board supports a direct connection with a 4x4 matrix keypad using the CSI lines: CSI_MCLK, CSI_D0...CSI_D6. The driver uses the i.MXL GPIO's internal pull-up, therefore your board does not need any additional external resistor. Connect the 4 (rows) lines of the keypad to CSI_MCLK, CSI_D0, CSI_D1, CSI_D2 (resp. PORT_A pin 3, 4, 5, 6) Connect the 4 (columns) lines of the keypad to CSI_D3, CSI_D4, CSI_D5 CSI_D6 (resp. PORT_A pin 7, 8, 9, 10) {add a big picture of the keypad link with APF_DEV_LIGHT} {add a big picture of the keypad link with APF_DEV_FULL}

3x4 matrix keypad connected to i.MX GPIOs

FPGA solution

Development are also ongoing to connect matrix keypads using the FPGA...

Test

Quick try

• If you have a graphical LCD connected to your board (= virtual terminal), then you should see what you type (if your keypad keys are mapped to alphanumeric keyboard keys).
• If you don't have any virtual terminal, but only the serial console (event0 may be event1 if you already have a running touchscreen):

 # cat /dev/input/event0

Then you should see weirds characters when pressing keyboard keys:

 �,~~_�,}�}�3T,QToT6,TT�,�;��, � �

• if the test wiped out your console, you can get it back with:

# reset

• if you want to see hexadecimal values of what your are receiving:

# cat /dev/input/event0 | hexdump
0000000 0283 0000 5a09 000e 0004 0004 0051 0007
0000010 0283 0000 5a30 000e 0001 006c 0001 0000
0000020 0283 0000 5a40 000e 0000 0000 .... ....

• If corresponding device node in /dev/input/ is not existing, then:

 # cat /sys/class/input/input0/event0/dev
 13:64
 # mkdir -p /dev/input
 # mknod /dev/input/event0 c 13 64

Deeper one

• use target/demos/keypad_test/ test tool

Links

• external links (for exemple: locomo driver model)