Keypad Interface
================

+--------+--------------+---------------------------------------------+------------------+----------------+
| Pin    | Signal       | Description                                 | type             | I/O            |
+========+==============+=============================================+==================+================+
| 72     | KP_COL[0]    | Keypad Column selection signals.            | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 73     | KP_COL[1]    |                                             | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 74     | KP_COL[2]    |                                             | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 75     | KP_COL[3]    |                                             | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 76     | KP_COL[4]    |                                             | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 77     | KP_ROW[0]    | Keypad Row selection signals.               | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 78     | KP_ROW[1]    |                                             | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 79     | KP_ROW[2]    |                                             | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 80     | KP_ROW[3]    |                                             | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| 81     | KP_ROW[4]    |                                             | VDDIO            |                |
+--------+--------------+---------------------------------------------+------------------+----------------+
| **Module**            | **Remark**                                                                      |
+-----------------------+---------------------------------------------------------------------------------+
| TX28                  | A PCA9554 8-bit I2C-bus I/O port is used for KP_COL[0-3] and KP_ROW[0-3].       |
|                       | KP_COL[4], KP_ROW[4] is not part of the keypad interface, used for CAN instead. |
+-----------------------+---------------------------------------------------------------------------------+
| TX25, TX48, TX53, TX6 | KP_COL[4], KP_ROW[4] can also be used for the 1st CAN interface.                |
+-----------------------+---------------------------------------------------------------------------------+

The Keypad Port (KPP) is designed to interface with the keypad matrix with 2-point contact or 3-point contact keys. The KPP is designed to simplify the software task of scanning a keypad matrix. With appropriate software support, the KPP is capable of detecting, debouncing, and decoding one or multiple keys pressed simultaneously on the keypad.

.. figure:: ../images/keypad_interface.png
   :align: center