ST AN2786 APPLICATION NOTE

AN2786

Application note

STEVAL-IHI001V1 demonstration board: washing machine user interface based on the ST7LITE49M and STLED316S

Introduction

The STEVAL-IHI001V1 is a demonstration board designed to simulate the user interface of a modern washing machine.

The board is based on the low-cost 8-bit ST7LITE49M microcontroller equipped with an I²C bus interface, and the STLED316S serial interfaced 6-digit LED controller with key-scan.

The demonstration board is designed to work as a stand-alone application, or as a motherboard for the STEVAL-IHI002V1 daughter board, which features the STMPE1208S capacitive sensing device and can be plugged into the STEVAL-IHI001V1 to operate as a capacitive single touch keyboard.

June 2008

Rev 1

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Contents	AN2786

Contents

1	STLED316S: serial interfaced LED controller with key-scan . . . . . . . .	3
2	Demonstration board application schematic . . . . . . . . . . . . . . . . . . . . .	4
3	Bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
4	STEVAL-IHI001V1 demonstration board photos . . . . . . . . . . . . . . . . . .	7
5	References and related materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	8
6	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	9

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AN2786	STLED316S: serial interfaced LED controller with key-scan

1STLED316S: serial interfaced LED controller with key-scan

The device used for the washing machine user interface is a compact LED controller and driver. It interfaces with the MCU through a simple 3-wire serial interface.

The STLED316S drives up to 56 LEDs connected in a common anode configuration. Individual digits may be addressed and updated directly, without re-writing the entire display panel.

The maximum segment current is set through a single external resistor (RSET).

Additionally, the STLED316S includes key scanning for an 8x2 key matrix, which automatically scans a matrix of up to 16 keys.

Figure 1. Product application diagram example

The STLED316S is equipped with an internal display RAM memory to store the data transmitted from the MCU through the serial interface.

The device is programmed through a variety of read/write commands that permit the user to set the display panel and manage the keyboard.

To avoid scanning the keyboard repeatedly searching for a pressed key, an additional IRQ signal can be connected to the MCU. An interrupt is generated whenever a key is pressed.

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