Design of Portable BD Player System

At present, it has become a trend that DVD players are gradually replaced by BD players. This trend will also extend to the field of portable optical disc players. At the 2011 CES in the United States, Sony, Philips, Sumsung, etc. followed Panasonic in launching their own portable BD players, which shows that this trend has already formed. Starting from the perspective of system solutions, this article elaborates on the design and development of portable BD players in detail, aiming to provide a solution and some ideas for domestic peers in the future when designing products, so as to avoid similar issues, improve development efficiency, and improve product quality and competitiveness.

System Hardware Composition

The entire system hardware composition is shown in Figure 1, including OPU, decoder, MCU, power battery management, key and remote control reception, LCD driver, HDMI output, USB, network interface, and switch detection. The functions of each component are described in detail below.

 

Figure 1 System hardware composition

OPU: Because the BD player needs to be compatible with DVD and CD, this module needs to be equipped with a laser head that can read data from three types of optical discs: CD/DVD/BD. Currently, products from Sanyo, Sony, etc. on the market can meet this requirement.

Decoder: The decoder of the BD player is required to be able to decode 1920×1080P full HD video signals, including H.264/VC-1/MPEG, etc. MTK and Broadcom chips can meet the requirements. The decoding chips listed in this article have built-in Ethernet, HDMI, ADAC and other chips, and have a high degree of integration. The actual selection should be based on the needs of product development.

MCU: MCU plays an important role. Because portable players have many functions, there is no single decoder chip on the market that can complete all portable functions. Therefore, a separate MCU is needed to assist the decoder to form the entire system and realize all the functions of the system. MCU is responsible for processing buttons and remote controls, controlling LCD driver chips, power management, battery charging and discharging processing, audio amplifiers, etc. At the same time, it interacts with the decoder through communication between the two parties to exchange commands and transmit information.

Battery power management: responsible for the power management of the entire system, including power on and off, switching between adapter and battery, battery charge and discharge, etc.
Buttons and remote control: handles input from the main body buttons and remote control buttons.

Switch: responsible for external switch and headphone insertion detection.

RTC: Real-time clock module, can be used as actual timing.

FAN: Fan, used to dissipate heat for the system; when the BD player is working, the chip operates at a high frequency and consumes a lot of power, so an external device is needed to dissipate heat for the main chip.

Over Current Protection: This chip is used to detect and protect the USB interface from overcurrent.

USB: used to connect external USB devices, expand the functions of the CD player, and play high-definition materials downloaded from the Internet.

Network interface: It has three functions: (1) BD live playback that meets BDA requirements; (2) corresponding software network upgrades. The software of BD players is complex, and BD specifications are constantly updated. Configuring this function can respond to market issues through the automatic upgrade function of the network after the product is launched, meet the ever-changing needs of the market, reduce consumer investment, and improve product competitiveness; (3) corresponding to various network application functions. [page]

The system software design

system is mainly composed of a decoder and an MCU. The decoder and the MCU coordinate through communication to complete the functions of the entire system. Therefore, the system software design includes three parts: the software design of the decoder part, the software design of the MCU part, and the communication design.

1. Software Design of Decoder

The decoder software is built on the Linux operating system, including device drivers, middleware and application layers. The modular design concept is adopted, and the system is divided into different levels and modules according to the system functions for implementation. The operation of different tasks is controlled by starting different processes.

The biggest difference between portable Blu-ray players and similar products in the past is that they can play Blu-ray discs and have rich network functions. The system structure of the decoder software is shown in Figure 2.

 

Figure 2 Decoder software system composition

2 MCU software design

The MCU software design uses a small operating system to manage two tasks. SubTask is used to communicate with the decoder, and MainTask is responsible for all processing other than communication. The entire system is divided into a driver layer, an intermediate layer, and an application layer. The driver layer includes hardware devices and OS, including terminal configuration, key input, switch detection, AMP, FAN, RTC, etc. The intermediate layer includes the various module interfaces that need to be provided to the application layer to implement specific functions and actions; the application layer is divided into UI, OSD and other modules according to the functions of the system to complete the various functions that the system needs to implement. The system structure of the MCU software is shown in Figure 3.

 

Figure 3 MCU software system composition

3 Communication Design

The communication between MCU and decoder can adopt a variety of interface forms at the physical layer, and UART is selected here. The design of the protocol layer needs to focus on two aspects. One is whether all the functions required by the system can be realized, and no mistakes will be made due to the incompleteness of the protocol design that affects the realization of system functions; the other is whether the abnormal handling mechanism of communication is well considered, which affects the reliability of the system, including the setting of the number of repeated transmissions when an error occurs, the setting of the waiting delay time when the communication is busy, etc.

Power

consumption design is very important for portable products. It not only takes into account the power consumed during normal operation, but also the power consumption during standby. Power consumption design involves many aspects of the system, including chip selection, circuit design, etc. Specifically for this system, it is necessary to discuss and verify the power consumption of the OPU part, the backlight of the LCD, the working power of the decoder, the peripheral circuit, and the power management during standby.