Speech recognition technology is to make the computer "understand" the human language, and then according to its meaning to the implementation of the corresponding order, in order to achieve human services. With the in-depth study of speech recognition, its technology has two main applications: one direction is a large vocabulary continuous speech recognition system, mainly used in computer dictation machines, and telephone networks or the Internet combined voice information query service systems, these systems are implemented on the computer platform; Another important development direction is the miniaturization, the application of portable voice products, most of these applications using a dedicated hardware system. With the advent of post-PC era, the latter development will become a very popular topic of speech recognition technology and embedded system cross-research, which will further promote the development of speech recognition technology to the intelligent direction.
Audio Interface Schematic
The system uses audio codec is UDAl341t33I. UDAl341 is a monolithic analog and digital-to-analog converter with signal processing capability. It is fully integrated analog front-end, including programmable amplifiers and automatic gain control circuit. With digital signal processing, it is ideally suited for use with digital audio equipment. UDAl341 support IIS bus data format, and $ 3C2440 connection is very simple, and has a DSP-specific playback mode, so it is very suitable for embedded voice recognition system development. Solution $ 3C2440 and digital audio codec UDAl341 data exchange between the use of the IIS bus. IIS (Inter-IC Sound Bus) is Philips bus digital audio equipment for the transmission of data between the development of a bus standard. In the Philips IIS standard, both the hardware interface specification, also provides digital audio data format. The IIS bus handles only sound data.
Other signals, such as control signals, must be transmitted separately. In order to make the chip pin out as little as possible, IIS only uses three serial buses. The three lines are: to provide multiplexing function of the data lines, field selection lines (channel selection), the clock signal line. At present, most of the audio codec chip and microprocessors support the IIS bus standard. Samsung 3C2440 microprocessor used in the system built-in IIS interface with the market a lot of voice processing chip is connected with good compatibility, while S3C2440 also provides a DMA data transfer mode, so you can not go through the CPU Direct data transmission, at the same time to achieve data transmission and reception, which in the embedded system resources are very limited conditions are very useful.