AN3128 datasheet(14/105 Pages) STMICROELECTRONICS

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Multi-input embedded GUI library

AN3128

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Doc ID 16918 Rev 5

Multi-input embedded GUI library

3.1

Introduction

The library supports touchscreen features and includes a low level driver which handles the

analog input (for 12-bit ADC), and a function for the touchscreen calibration based on an

algorithm using 5 points.

The multi-input embedded GUI firmware library is fully developed in 'ANSI-C' following an

OOP approach. This means that the final application uses instances of page and graphic

objects according to their public methods and properties. In the end the PageObj is a

structure containing public properties (data fields) and methods (functions pointers). The

OOP encapsulation feature is assured.

The library can be included in the final application as a library file (multi-input embedded

GUI library.a) and used as a black box through its exported public API, or included in the

final application as source files (.c and .h) if the user wants to debug the library itself, and/or

change the HAL functions in order to port the library on an LCD different (in model and

resolution).

The calibration process is part of the post-processing layer. The touchscreen must be

calibrated at first power-on and/or upon user request.

Once the calibration is done, on future power-on of the board it does not have to be run

again because the calibration parameters are saved on the Flash memory.

3.2

Graphic object introduction

This solution enables designers, comfortable with the use of standard microcontrollers, to

create higher-end “look and feel” human interfaces by replacing conventional

electromechanical switches with touch sensing controls.

Designers can combine touch sensing functions using multiple configurations (touchscreen,

joystick, and keys) with traditional MCU features (communication, LED control, beeper, LCD

control, etc.).

The multi-input embedded GUI library is part of the application firmware.

Maturity, robustness, flexibility, and performance, with good time-to-market, make this

solution simple to implement to develop any kind of application.

The graphic objects are a set of controls that can be printed on the screen and associated to

an action when pressed.

The library has been developed and tested on an LCD panel of QVGA resolution (320x240)

which is the default, but the library is independent to the LCD resolution, although it has not

been tested with others.

The library has been designed to have the minimum memory footprint possible.

The reserved Flash memory footprint requirement depends on the application configuration.

It is therefore not possible to specify a precise value, but normally for a “typical” user

application, 64 Kbytes of Flash memory are needed (the images are stored in ROM).

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