Design of DVD processor ES60X8 in car audio system
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Abstract : This paper briefly introduces the ES60X8 series DVD processor, and gives the structure of the car DVD audio system based on ES60X8, the interface design between each module; the electronic seismic design and PCB anti-interference design of the external SDRAM are introduced.
Keywords :DVD; car audio; electronic anti-seismic; PCB anti-interference design
Introduction In recent years, with the rise of China's automobile industry, the related automotive multimedia technology has also flourished. The current automotive multimedia is mainly focused on audiovisual technology. The maturity of DVD technology has brought people the audio-visual effects of higher definition, more perfect hearing experience and longer playing time, which represents the development direction of the current car audio industry.
Car audio design has higher requirements than home audio design: due to the small space of car audio and high ambient temperature, it is necessary to consider more anti-high temperature anti-jamming design; at the same time, there is often uneven road surface and a bumpy operating environment. This is to consider the anti-jamming design of car audio.
The car DVD sound system introduced in this paper has the characteristics of modular design, integration, generalization, superior sound image performance and good shock resistance.
Figure 1 system structure diagram
There are two basic implementation methods for the system structure audio system's encoding/decoding system: one is to use a high-speed general-purpose microprocessor such as a DSP chip, and the DSP chip has both the encoding/decoding function and the system control function, which has better flexibility and Adaptability. However, high DSP performance, development requirements and cost requirements are not conducive to mass production by manufacturers. The other is to build a dedicated dedicated video chip with a low-performance master CPU. Compared with the full self-developed design using DSP, the second scheme will greatly reduce the hardware scale, shorten the development cycle, enhance system reliability, and reduce production costs.
This system adopts DVD processor ES60X8 and main control CPU TMP87CH47U as the main components, which can realize audio playback in CD, VCD, MP3, DVD and other formats. The ES60X8 family of DVD processors is a product of ESS that includes two parallel processing units, a RISC processor, a vector engine, and additional hardware resources to perform specific encoding/decoding tasks. These resources are connected to two separate data buses. The ES60X8 has a built-in video DAC, video encoding, and direct output of analog video signals, effectively simplifying peripheral circuits. The data read by the servo circuit directly outputs the analog video signal and the digital audio signal via the ES60X8; the ES60X8 uses the EPROM as the program/data external memory and the SDRAM as the display memory. Since the ES60X8 performs all processing on audio/video signals, the master CPU does not require an address/data bus, so the master CPU only needs to control the ES60X8 and handle the LCD display panel and remote control operations. The system structure diagram is shown in Figure 1.
The main components used in the system are:
* ESS's 208-pin QFP packaged DVD processor ES60X8 performs MPEG1, MPEG2 audio/video data stream processing. The ES60X8 supports DVD-Video, DVD-Audio, Video CD 1.1, 2.0, 3.0, Super Video CD (SVCD), CD-DA, MP3, Kodak Picture-CD. At the same time, four 10-bit video DACs are built in to provide analog video signal output, eliminating the need to add video DACs to peripheral circuits.
* The system main CPU uses Toshiba's 44-pin QFP package TMP87CH47U. It is an 8-bit high performance microcontroller with a frequency of 8MHz. Complete configuration including CPU core, ROM, RAM, I/O port, etc. It also has a Watch Dog timer, five power-saving modes, and provides a large current output capability that can directly drive the LED.
* The audio D/A component uses a 24-bit WM8706 with a maximum sampling frequency of 192KHz and a stereo DAC with volume control.
Figure 2 DMA mode connection diagram
Peripheral interface design of ES60X8
The peripheral interface design of the ES60X8 in the car audio mainly includes: interface with the main control CPU, interface with the audio DAC (WM8706), interface with the program/data memory EPROM, and interface with the servo circuit.
ES60X8 and main control CPU interface ES60X8 provides VFD (Vacuum Fluorescent Display) interface.
Since the car DVD system generally requires the system main control CPU to operate at low power even when the disc is not in use, the current time display on the display panel is provided, and the main control CPU outputs a standby control signal to the ES60X8.
The main control CPU provides the VFD clock signal and VFD control signal to the ES60X8; the ES60X8 provides the serial VFD data signal to the main control CPU through the VFD interface.
Interface between ES60X8 and Audio DAC (WM8706) The audio interface of the ES60X8 is a bidirectional serial port that can be connected to an external ADC/DAC to provide PCM audio data in I2S format. The ES60X8 offers two audio interface modes:
* Stereo, using the TSD0 pin to transmit serial audio data.
*AC-3 and DTS5.1 sound effects, using TSD0~TSD2 to transmit audio data.
This system uses stereo sound. The ES60X8 provides audio DAC clock, audio data output (pin TSD0) and audio transmission frame synchronization signal (pin TWS) to the audio DAC (WM8706).
ES60X8 and EPROM interface ES60X8 external EPROM as boot screen data and partial display program memory.
ES60X8 and servo circuit interface The system uses the Sanyo DVD movement, which uses a dual-head design to read DVD, VCD, CD, MP3. The movement is equipped with a random servo circuit, which simplifies the system design and saves development costs.
The interface between the ES60X8 and the servo circuit mainly includes control signals and 16-bit data signals.
Electronic seismic design: 16MB SDRAM
A typical home DVD player does not have a violently shaken external playback condition when playing a disc, so that there is no need to consider the earthquake resistance of the player; however, the operating environment of the car DVD player is greatly different. Due to the small unevenness of the general road surface, it will have a certain impact on the playback of the disc, such as a slight stagnation of the playback; in the case of a large amplitude of vibration (this is an inevitable situation of the vehicle system), there is no earthquake resistance. The player of the ability will have a long pause, and it may take 4-8 seconds to resume normal reading.
Our car DVD system is mechanically designed with TPE silicone oil damper damping. At the same time, a 16MB SDRAM is added to the circuit design as an electronic anti-seismic device, which keeps it smooth even under large and long-term vibration conditions. Playback effect.
The ES60X8 provides a 16-bit interface that interfaces with SDRAM/EDO as a video memory for DVDs. The ES60X8 external memory interface can address up to 128 MB, so the external SDRAM/EDO has a maximum storage capacity of 16 MB.
The SDRAM with a capacity of 16MB and an access time of 9ns is enough to complete the access to the memory in two clock cycles, and the bus access can be completed with zero wait. The system is designed to pre-read the DVD data into the SDRAM and then decode the data in the SDRAM. Since the standard single-sided single-layer DVD has a capacity of 4.7 GB and a playback time of 135 minutes, ideally, 16 (MB) * 135 (minutes) * 60 (seconds / minute) / (4.7 * 1024 (MB)) = 27 The seismic effect of seconds. In fact, due to low software efficiency and other reasons can not reach 27 seconds, the measured results can be shocked for about 6 seconds. In order to achieve longer earthquake resistance, software access efficiency should be improved in software.
The PCB layout of the SDRAM should be noted that the signal lines should be placed on the component layer, and the shortest possible wiring should be used, and the vias should be as small as possible to reduce the reflection caused by the discontinuity of the signal path. When the clock signal line of the SDRAM is arranged, since the clock frequency is the same as the operating frequency of the decoder, care should be taken to rationally route to reduce mutual interference.
At the same time, in order to speed up the transmission of large amounts of data, the DMA is used between the ES60X8 and the SDRAM for data transmission without taking up resources of the ES60X8 to ensure its decoding speed. The ES60X8 has a built-in DMA bus controller that provides 32-bit data exchange for the following channels: video data bus and memory; video decoder and memory; ESS RISC and memory; ESS RISC and video data bus. Figure 2 is a DMA connection diagram of the ES60X8 and 16MB SDRAM.
The DSCK of the ES60X8 provides the clock signal of the SDRAM; and, the output control signal to the SDRAM. DB00~DB15 are data lines, and MA00~MA11 are address lines.
Anti-jamming design
Crosstalk problem When I was debugging, I encountered the problem of not being able to properly rotate the disc. Finally, I found that the connection between the two grounds of the board was too slender, causing problems caused by the resistance of several tens of milliohms.
Since the digital signal and the analog signal are present in the DVD player, as in the present system, the analog signal is generated through the video/audio D/A, and the audio analog signal needs to be amplified by the amplifier. Therefore, when designing the PCB, the analog ground and the digital ground should be separately routed, and finally connected to the power ground at one point to prevent signal crosstalk. The power and ground wires should be as thick and wide as possible. In addition to reducing the voltage drop, it is more important to reduce the coupling noise.
High temperature problem Because the car audio system requires small size (length and width are 182mm*53mm*160mm), the narrow space is not conducive to air convection, plus it is usually installed in the front of the car, close to the engine, poor ventilation, external temperature acceleration Machine heating process. Moreover, the built-in power amplifier generates a large amount of heat. Generally, after running for a few minutes, the temperature of the power amplifier IC can reach 100 °C. If the temperature of the crystal element that generates the clock signal is too high, the drift of the operating point will occur. Therefore, compared with the general home DVD player, the car DVD system design must additionally consider the reasonable layout of components and adopt appropriate cooling measures.
The key components of the car DVD system that are sensitive to temperature are all special components for car audio that require high temperature resistance. For example, the MPEG2 decoding IC ES60X8 has an operating temperature of 0°C to 70°C, and the high-efficiency power amplifier IC (TDA7454) has an operating temperature of -55°C to 150°C.
At the same time, the rear panel of the player has an area to increase the heat dissipation of the aluminum alloy, and the high efficiency amplifier
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