Cars require a special combination of information and entertainment systems. Today's infotainment electronics use a true multimedia approach. Automotive infotainment systems need to provide relevant information for the operation of car drivers, and such information is often critical. The driver listens to entertainment, traffic reports and information from satellite navigation systems. Passengers in the back seat want to add video entertainment content to the system.
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Design problem
In addition to the basic task of aggregating and reliably presenting information to drivers and passengers, another problem is to provide users with a reliable and practical way to control the system. In addition, the harsh environment encountered by automotive electronics must also be considered. Voice activation and control provide advanced security, but implementation in noisy environments is not an easy task. In addition, the car itself must also consider the footprint and weight of the system, and thermal management is also key.
Even considering only the audio system design can present a complex situation. The hardware needs to handle different transmission methods and component coding. CD, SD and Mini-SD cards and portable MP3 players must be able to adapt to all common formats. In addition to audio CDs, the system's CD player should be able to cover data transfer types like ISO9660 and CD-ROM.
Decoding audio files is not a trivial task. Users want the system to adapt to all common file formats of MP3, AAC, WMA and ATRAC with good sound quality. In higher-level systems, audio-based information (such as traffic reports) needs to be decoded and included in the system output.
Car audio CD players are prone to vibration, so pay attention to the large amount of memory that is required to maintain real-time audio output when the disk is out of read. Such RAM memory can add significant cost and overall footprint. Less component and high integration are beneficial to the automotive environment. The equipment used in automobiles also needs to have a low-power special mode. When the car engine is turned off, the infotainment system should be prevented from continuing to consume power from the battery.
Multimedia system chip
The emerging integration solution simplifies the designer's task of making more audio functions fill the available space. The latest integrated system-on-a-chip (SoC) solutions include Toshiba's TC94A34, TC9A70FG (Zipang-1) and TC94A73 MFC (Zipang-2) solutions. These three devices are highly integrated, giving designers the flexibility to decide whether to purchase a complete solution or rely on their own IP and design experience to implement key parts of the design. All three devices offer a full range of audio decoding capabilities. The TC94A70FG adds a CD control circuit; the TC94A73MFG is a single package system (SiP) solution that integrates FCRAM (fast cycle RAM) for ESP (Electrical Shock Protection).
The use of integrated devices greatly simplifies the implementation of vehicle multimedia systems by reducing component count and without system processor unlocking. Zipang IC's achievable features include CD-DA playback mode (with CD-text), compressed audio playback, ISO9660 disk analysis and control, audio playback and data transfer in CD-ROM mode. Digital filters, balance and dynamic range control, and sound domain control are also available without the need for additional components.
The audio decoding DSP features of the new device include support for MP3, WMA, ATRAC3, ATRAC CD and AAC audio formats. The dedicated CD features include a digital servo system processor with integrated RF amplifier and audio DAC.
All three devices offer a parallel interface and a 4-wire serial interface for direct connection to the microcontroller. Serial digital audio and analog interfaces (3 I2S inputs, one I2S output and one SPDIF connection) provide flexibility for audio input and output).
Applications
A typical CD/Audio system architecture based on the new device (Figure 1) includes the MCU, Zipang device, microcontroller/firmware, CD and SD card hardware.
In this example, the CD driver communicates with the Zipang device through the I2S interface. In the case of a fully configured IC, CD head amplification, sync amplitude difference protection and insertion, demodulation, error correction and servo system control can be handled. The PCM data read from the CD is fed into an integrated audio DAC that supports standard PCM audio timing inputs and outputs and includes built-in digital filtering.
In fact, the communication between the microcontroller and the Zipang device is slave to the main master MCU and can be selected via a parallel or serial interface. The TMP91CY22F micro, which uses Toshiba's patented voice IP, can receive incoming traffic information. Encoding this information saves memory space and decodes the message to provide the driver with the latest traffic information they want. In addition, an additional EEPROM can be added for permanent traffic information storage, which is connected to the microcontroller via SPI.
The TMP91CY22F micro itself performs the procedures required to read and manage data files from the SD card, transfer ID3 tags from music files and provide user functions (such as playlists and hybrid playback), as shown in Figure 2. The entire system architecture requires as little power as possible. When not in use, the device is in sleep mode and is "awakened" under event control when not in operation. In the case of an SD card reader, inserting a card will wake up the entire system program, which is done under micro control. The controller itself can initiate system operation via its internal timer or the host provides wake-up input to the micro and Zipang devices.
Conclusion
The architecture described in this paper demonstrates the integration of multiple content sources and multiple data formats in a vehicle environment to increase performance and drive capabilities. This trend will continue, and vehicle audio devices will require increased complexity as audio technology evolves, while components Need to include the added codec.
The device will also continue to increase integration, further reducing component count, power consumption and host overhead. As this structure is widely adopted, the demand for development systems will also increase in order to accelerate time to market.
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