Two-way digital TV Dream box Design and Implementation

With the development of network technology, particularly the development of optical network technology makes the backbone of the bandwidth of tens of Gbps. At the same time, the optical transmission network continued declines in the price of optical fiber transmission system in the cable network received a large number of applications, from traditional developed into a hybrid fiber coaxial cable coaxial cable (HFC). HFC is used in the optical transmission backbone network system and the access part of the hybrid coaxial cable network

Currently, from a functional point of view, dream box can be divided into three categories: First, digital satellite dream box (also known as satellite integrated receiver decoder); second, cable dream boxes; third, Internet dream box STB. The hardware structure of the different functions works with big difference, but the basic composition is generally a high-performance processor core, memory, communication interfaces, data decoder, video and audio image processor, television encoding and interface, peripheral interfaces. 

Figure 1 composed of a dream box diagram and the entire hardware system is divided into several sub-systems: MPEG decoding, audio, video and graphics processing, cable modems, high-performance embedded microprocessor, memory and peripheral interface circuits.

Interactive digital dream box software is a real-time operating system (RTOS) as the core. According to the system hardware architecture and design, it expands the current system functions and the common operating systems, such as Wind River System the company's VxWorks, Integrated Systems Incorporated's pSOS, Microware's DAVIDOS- 9, ST's OS20, Windows CE, and the development of Power TV for set-top boxes, etc. In addition, there is a real-time open source operating system Linux which can be configured through a set of embedded real-time operating system.

In the bottom of the operating system kernel, there is a hardware abstraction layer (HAL). HAL directly controls the access by the hardware. And through a set of macros to other machine-independent code with the provision of services, the system greatly simplifies the porting work RTOS kernel. If the hardware platform changes, besides the device drivers, you can just change the hardware abstraction layer code on it.