ST AN2422 APPLICATION NOTE

AN2422

Application note

STMPE2401 GPIO port expander

Hardware interface guide

Introduction

STMPE2401 is the first in the ST family of I/O port expanders. The principle of a basic I/O port expander is that it provides additional I/Os that can be used by the host processor to implement additional features such as increased number of inputs/outputs, expanding the number of control signals and mixed signal lines, controlling a greater number of peripherals without resorting to an additional Complex Programmable Logic Device (CPLD) or upgrading the central processing unit (CPU).

In addition to these basic features, the STMPE2401 comes with integrated intelligence to implement advanced features such as keypad scanning, PWM control, rotator dial control, etc.

The STMPE2401 can be widely used in the fields of mobile communications, portable media players, game console, mobile phones, smart phones, consumer electronics and computer peripherals like state-of-the-art printers, advanced embedded systems, etc.

This application note deals with the setup and hardware interfacing of the device to perform various functions and the different modes for reducing power consumption.

January 2007 Rev 1 1/19

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Contents AN2422

Contents

1 Advantageous features of STMPE2401 . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 STMPE2401 Hardware description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.1 STMPE2401 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2 Power supply and ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.3 32-kHz crystal oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4 I2C Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.5 Reset pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.6 Interrupt pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.7 Initialization and configuration of Interrupt Controller . . . . . . . . . . . . . . . . 10

2.8 GPIO state description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.9 Configuring the GPIO Alternate Function register . . . . . . . . . . . . . . . . . . 11

2.10 GPIO Hotkey feature description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.10.1 GPIO Hotkey programming sequence . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.10.2 Minimum pulse width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.11 Modes of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.11.1 Operational mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.11.2 Sleep mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.11.3 Hibernate mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

2.11.4 Typical ICC values in various modes . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.12 Power-up sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.13 Tips for hardware troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4 Reference documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

5 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

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AN2422 Advantageous features of STMPE2401

1 Advantageous features of STMPE2401

1. A highly flexible interrupt system eliminates the need for polling and reduces CPU usage

2. Low power consumption

3. Wake-up from Sleep mode

4. Easy-to-use driver software

5. Flexibility in the configuration of individual GPIOs

6. Simpler connection to CPU (just two I communication

7. Combinational keys to enhance gaming experience

8. Applications: Mobile phone keypads, all-in-one printers, game consoles, embedded systems, portable media players, etc.

Figure 1. Concept of GPIO port expander

C lines + Interrupt pin) for configuration and

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STMPE2401 Hardware description AN2422

2 STMPE2401 Hardware description

The STMPE2401 is a GPIO (General Purpose Input/Output) port expander able to interface to a digital application-specific integrated circuit (ASIC) via the two-line bidirectional bus

C).

A separate GPIO Expander IC is often used in Mobile-Multimedia platforms to solve the problems of the limited GPIOs usually available on the Digital Engine.

The STMPE2401 offers great flexibility as each I/O is configurable as input, output or in specific functions, to scan a keyboard, provide PWM outputs for brightness control in backlighting or in a rotator decoder interface. This device is designed for use with a very low quiescent current, and includes a wake-up feature for each I/O to optimize the power consumption of the IC. The main features of the port expander device are:

● 24 GPIOs

● Operating voltage 1.8V

● Hardware keypad controller (8*12 Matrix maximum)

● 3 PWM (8-bit) outputs for LED brightness control and LED blinking

● Interrupt output (open drain) pin

● Configurable hotkey feature on each GPIO

● Ultra-low Standby-mode Current

● Small Package TFBGA - 36 pins, 3.6x3.6mm and 0.5mm pitch making it optimal for use

in portable applications such as mobile phones with critical space constraints.

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AN2422 STMPE2401 Hardware description

Figure 2. STMPE2401 block diagram

Keypad

Controller

GPIOs

7:0

Keypad

Inputs

Function

Select

Keypad Inputs 7:0 GPIOs 7:0

INT

SCLK

S DATA

Controller Core

+PWM +Rotator Control +GPIO Control

I²C Interface

GND

Keypad

Outputs

Function

Select

GPIO

PWM

O/P

POR

RC Oscillator

Clock

Controller

XTALIN XTALOUT

Keypad Outputs 11:0 GPIOs 14:8 and 20:16 Rotator

GPIO 15 Addr0

PWM1, 2 and 3 Addr1 GPIOs 23:21

Reset_N

CC1

CC2

CC1

CC2

Ai12531

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STMPE2401 Hardware description AN2422

2.1 STMPE2401 pin description

Ta bl e 1 describes all the pins on the STMPE2401 device.

Table 1. STMPE2401 Pin list

Pin Name Type Description

1GND -

2 KP_X0 IO GPIO

3 Reset_N I External reset input, active LOW

4 KP_X1 IO GPIO

5 KP_X2 IO GPIO

6 KP_X3 IO GPIO

7 KP_X4 IO GPIO

8 KP_X5 IO GPIO

9 KP_X6 IO GPIO

10 GND -

11 V

CC1

12 KP_X7 IO GPIO

13 KP_Y5 IO GPIO

14 KP_Y4 IO GPIO

15 KP_Y3 IO GPIO

16 KP_Y2 IO GPIO

17 KP_Y1 IO GPIO

18 KP_Y0 IO GPIO

19 GND -

20 ADDR0 IO GPIO and I

21 KP_Y9 A/IO GPIO

22 KP_Y10 A/IO GPIO

23 KP_Y11 A/IO GPIO

24 PWM3 A/IO GPIO and I

25 PWM2 A/IO GPIO

26 PWM1 A/IO GPIO

27 V

CC2

28 GND -

29 INT O Open drain interrupt output pin

30 KP_Y8 IO GPIO

31 KP_Y7 IO GPIO

32 KP_Y6 IO GPIO

33 SDATA A I

34 SCLK A I

35 XTALIN A XTAL oscillator or external 32-kHz input

36 XTALOUT A XTAL oscillator

- 1.8V Input

C DATA

C clock

C ADDR 0 (in reset)

C ADDR 1 (in reset)

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