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Design of LCD System Based on Graphics Library Transplantation Technology

Keywords: LCD, STM32, emWin graphic library, transplantation technology

Abstract. In order to satisfy the personalized design of modern electronic products for LCD system,the transplantation technology is applied in this paper, which is based on STM32 MCU and the application of emWin graphics library. According to the function of the superiority of STM32 MCU and emWin graphics library, the hardware is designed, and the transplantation of emWin graphic library is finished on STM32 platform for the LCD display system. The LCD display system that has good practical effect is verified through practical experiment, of which results show that the LCD display system is steady, reliable, and friendly to the users.

Introduction

At present, with the constant improvement of manufacturing technology and the decrease of production cost, the liquid crystal device becomes one of the most widely using electronic products for display function due to the superiority, such as small volume, low power consumption, long service life and less produce electromagnetic radiation pollution[1]. LCD can display complex signal and images which other same cost products can not. With the advantages, it would have wide development prospects in the field of display terminal in the future.

Fig.1 Hardware composition and connection

STM32 microcontroller is one kind of ARM processor of 32-bit that produced by STMicroelectronics (ST) company [2]. The processor has rich internal resources, strong extended ability, low power consumption, and great cost performance. As a result, it has gradually become the ideal to 32-bit microcontroller device. EmWin graphics library is one kind of general graphics software used for embedded development that can support any CPU and almost all of the display, of which modules are designed by using C language source code [3]. At the same time, because the emWin graphics library source code is open, it becomes easily for the designer to operate. Therefore, combine the advantages of STM32 microcontroller and EmWin graphics library has a positive practical application value.

Hardware design scheme

Hardware composition. During the design scheme of liquid crystal display system, STM32F103 series microcontroller is selected as the main control chip. According to the actual demand, the basic function consists of data receiving, conversion, alarm and display. System hardware composition and connection is shown in Fig.1, the system hardware is mainly composed of STM32F103 microcontroller, CAN bus interface, LCD interface, alarm output interface. At the same time, the hardware system also includes power supply, extension, Flash, buttons and alarm, and other peripherals.

Fig.2 Hardware composition

STM32F103 MCU. STM32F103 series microcontroller is a new generation of embedded ARM processor based on ARMv7-M system structure. Its internal is adopted standard 32-bit RISC (reduced instruction set), which provides high code efficiency [4].The controller specific models of liquid crystal display system that used is STM32F103VCT6, with the highest working frequency of 72 MHZ and Working voltage of 2.0-3.6 V. The modes contain dormancy, stop, and standby power consumption. Multiple communication interface, timer, interrupt source and peripherals have provided wide method to achieve superior function. In addition, the microcontroller has integrated the FSMC internal SRAM controller (flexible), which can directly support 8080 bus interface of the LCD controller [5].

According to ILI9320 LCD control principle of the controller, the internal RAM can be viewed as static random access memory without the address bus. The STM32 microcontroller is working through the corresponding GPIO port under the FSMC bus way, in accordance with the requirements for 16 bit 8080 parallel, of which interface access LCD controller, realize to control the LCD controller driver. The working process is shown in Fig.3.

Fig.3 Working process Fig.4 Schematic diagram of emWin layer structure

Software design scheme

EmWin layer structure. As a kind of complex efficient graphical user interface, emWin can be transplanted to many display controller and operating system with modular characteristics and hierarchical structure. As shown in Fig.4, emWin mainly includes application layer, the graphics library layer and drive layer. In the process of emWin layer structure, the function of the application layer is called from the graphics library layer function, and then the functions through the drive layer is from the bottom for the realization of the hardware circuit drive and display interface.

LCD file configuration. LCD file is mainly worked for the configuration of the LCD controller. According to the parameters of the LCD screen, the corresponding macro definition is modified by LCD file, which can complete the setting of display size, direction, LCD color mode and the display driver configuration. On the other hand, according to the LCD interface circuit connection situation, LCD controller command and data configuration register address is finished. The configuration is as follows:

#define XSIZE_PHYS 240

#define YSIZE_PHYS 320

#define COLOR_CONVERSION GUICC_565

#define LCD_CONTROLLER 9320

#define DISPLAY_DRIVER GUIDRV_ FLEXCOLOR

#define LCD_REGnot;_ADDRESS (

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