Abstract: This article designs a single-chip MP3 player, using the open source software project EFSL, taking advantage of its small memory requirements, simple transplantation, and completely free of charge. By designing the underlying driver, the FAT file system based on the SD card is transplanted on the LPC2148. And use CrossWorks for ARM 1.6 software to configure and compile the EFSL file system. Through software debugging, the correctness of the design is verified. This design provides a new way for the function expansion of single-chip microcomputer applications.

Introduction

In recent years, with the development of digital technology, people's requirements for MP3 players have become more diversified. Manufacturers have made a lot of efforts in the selection, design, development, additional functions and applicable fields of MP3 players. Various schemes have been designed. Under the trend of faster and faster processors and larger and larger storage capacity, the storage organization and storage settings of data in products need to be efficiently and reasonably managed, which is exactly the function of the file system.

The embedded file library (Embedded FlieSystemLibrary, EFSL) of the open source software project relies on its advantages such as small memory requirements, simple migration, and completely free. As an embedded file system, it is very suitable for solving the problem of storage space management and function expansion of small single-chip microcomputers. This article designs a new type of embedded MP3 player based on EFSL file system and ARM platform, which has certain practical value. At the same time, it provides a feasible reference solution for the single-chip microcomputer to get rid of the operating system and realize the multimedia application of the single-chip microcomputer.

1 Hardware design

The block diagram of the system hardware structure is shown in Figure 1. The entire hardware system uses the LPC2148 of PHILIPS 'ARM7-TMDI core as the core processor, and controls the VS1003 decoding module, SD card interface module, USB interface module, and human-computer interaction function module, respectively.

Figure 1 Block diagram of the hardware structure of the MP3 player

Figure 1 Block diagram of the hardware structure of the MP3 player

1.1 Main control chip

LPC2148 is a 16 / 32-bit ARM7TDMI-S microcontroller that supports real-time simulation and embedded tracking. It is embedded with 512 KB high-speed FLASH memory. Because of its powerful functions, it is easy to upgrade the system in the future.

In this system, only USB, SPI, SSP interface functions and ADC functions are used temporarily. The use of other functions is subject to expansion. The decoding module VS1003 integrates the VS_DSP processor, stereo audio DAC and stereo headphone amplifier driver. Since the decoding and the control chip are separated, the sound quality is good and the control is relatively simple. LPC2148 controls VS1003 through its SPI interface.

1.2 Display module

The display module uses VGS12864E, which is a 128 & TImes; 64-line dot matrix OLED monochrome, character, and graphic display module. The module has a built-in 64 & TImes; 64 display data RAM, where each bit of data corresponds to the light and dark state of a dot on the OLED screen; its command system is compatible with the LCD display drive controller HD61202. This system uses 8-bit I / O port to connect with 8-bit data bus D0 ~ D7 of OLED module through analog time sequence, and then through the 3-bit I / O port to the LCD command control or data operation bit RS, read and write control bit R / W is connected to the enable control bit E to control the OLED module.

1.3 Storage module

The SD card is used as a storage medium, which has the advantages of large capacity, small size and vibration resistance. All songs are stored in the SD card, and the SD card works in SPI mode. Connect the SD card by setting the SSP of the LPC2148 to the SPI function. At the same time, the other two I / O ports of the chip are set to detect that the card is fully inserted into the card holder and whether the card is write-protected.

2 Software design

The player uses a four-layer structure to achieve its functions. The software hierarchy is shown in Figure 2. The main purpose of modularization is to facilitate the portability of modules.

Figure 2 Player software hierarchy

Figure 2 Player software hierarchy

DC cable connector diameter (d) is 2.1mm, diameter (D) is 5.5mm, thickness (B) is 10mm. 

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