FTA DVB-T set-top box solution based on CheerTek CT212T

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Main chip structure and main functions

The CT212T is a highly integrated SoC from CheerTek for FTA DVB-T STB products. The chip integrates MPEG A/V decoding, demultiplexing, TV encoder and microprocessor, etc. The FTA DVB-T set-top box designed with this chip is cost-effective. The CT212T chip architecture is shown in Figure 1.

Figure 2: Schematic diagram of the hardware structure of the FTA DVB-T set-top box using CT212T

The CT212T integrates an 8-bit Turbo 8032 core processor with a maximum operating frequency of 50MHz. The system functions that can be implemented include: code stream decoding according to ISO/IEC 13818 standard; support for digital TV and set-top box electronic program guide (EPG); support for teletext .

Machine architecture

1. Front end module

Terrestrial digital TV is currently divided into two application areas: fixed reception and vehicle reception. Front-end modules with different COFDM chips can be selected for different application areas to achieve the highest price/performance ratio. For the fixed reception we choose Zarlink's MT352, the related front-end module products can choose DVB-T tuner (Tuner) module of Samsung, LG and other companies; for the car receiving DiB3000MC or DiB3000P which choose DiBCom here, the chip introduces new channel Estimation and Doppler effect compensation algorithms, as well as better co-channel interference processing, are superior in high-speed mobile reception, and related front-end module products such as Empire's DVB-T Tuner module.

Figure 3: FTA DVB-T home set-top box decoder board physical photo

2. Memory module

The solution is designed to use one 8Mb flash, two 16Mb SDRAM, and one 2Kb EEPROM. The flash memory is used to store the set top box running program; the EEPROM is used to store the user boot state and the channel parameters; the SDRAM is used to store the audio and video decoded data, the OSD bitmap, and also store the data of the application running time.

3. Output module

The output includes audio and video output and serial output. The video output provided by the solution includes CVBS, Y/C, RGB, YcrCb and progressive YpbPr output, and the output interface can be designed as an interface such as RCA, S-video, and Scart. The audio is amplified by external PCM decoding. In addition to the stereo left and right channels, mono, the system also provides S/PDIF digital audio output.

Design

The following is a description of the specific design of the FTA DVB-T home set-top box based on CT212T. The physical picture of the decoder board is shown in Figure 3.

1. Selection of key components

For DVB-T Tuner, we tested three Tuner, Samsung TDTC9251DV1C (TUA6034T+MT352), Empire DTN-352EU (TUA6034T+MT352), and Empire DTN-366EU (TDA6651+MT352). The test data is shown in Table 1. Finally selected Empire DTN-366.

Figure 4: Structure of the FTA DVB-T home set-top box system.

The system architecture of the program is shown in Figure 4. For the European and Middle Eastern markets, the European standard Scart video output interface is required. We use 4053 to switch.

2. Software Architecture

Figure 5: CT212T FTA DVB-T set-top box software architecture

The CT212T software system architecture is shown in Figure 5. The public version of the program provided by CheerTek opens up the source code of the NIM Driver, OSD, front panel, TV encoder, etc. Users can easily modify the corresponding software modules according to the adjustment of their own hardware.

Program characteristics

Fengbao's FTA DVB-T set-top box solution is compliant with DVB-T and MPEG II standards and supports 6M, 7M, 8MHz, 7MHz & 8MHz for software setup; it also supports OSD & VBI graphics output, multi-language subtitles and EPG. The software can be upgraded through RS-232 port to support machine-to-machine upgrade; it can perform forced or automatic PAL/NTSL switching, and supports various video output such as CVBS, YC, RGB, YcrCb and progressive YpbPr. Other features include: support for parental lock function; low power standby; time correction; support for 4:3, 16:9 conversion; support for S/PDIF digital audio output; search for all frequencies of UHF and VHF.