November 2006

Rev 1

1/6

AN2421

Application note

Using the STMPE801 as a keypad controller

Introduction

STMPE801 is an 8-bit general purpose port expander device in the STMicroelectronics Port

Expander Logic family. Its eight GPIOs (General Purpose Input Output) are connected to the

host system using a standard I2C connection.

This application note explains how to control an 8*8 (64-key) matrix keypad using the 8

internal GPIOs of a base-band processor and the 8 GPIOs of the STMPE801 port expander.

The simplified schematic is shown below.

Schematic for using STMPE801 as a keypad controller

Baseband

BB_GPIO

STMPE801

801_GPIO

SDAT

SCLK

INT

RST

8*8

Keypad

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