1 based on LPC2214 and uC/OS-II embedded platform
At present is popular the ARM chip essence has ARM7TDMI, ARM720T, ARM9TDMI, ARM992T, ARM940T, ARM946T, ARM966T and ARM10TDMI and so on, Philips LPC2214 is based on the ARM7TDMI-S high performance 32 RISC micro controller, it integrated the Thumb expansion set of instructions, 256KB has been possible internal Flash which programmed in the system and may 16 KB RAM which programmed in the application, the vectored interrupt controller, the external bus controller, 2 UART, I2C serial interfaces, 2 SPI serial interfaces, 2 timers (7 capture/compared channel), might provide reaches 6 PWM the output the PWM unit, 8 channel 10 ADC, real-time clock, watch-dog timerAs well as 112 general I/O pins, (PLL) may realize LPC2214 through the programmable internal phase-locked loop most to be high are the 60MHz CPU clock rates, the relatively numerous ARM serial products, Philips Corporation produces LPC2214 is a section of performance-to-price ratio high ARM7 chip.
The embedded real-time operating system is helpful in enhances the system reliability and the development efficiency, and can display 32 CPU fully the multitasking abilities, the common embedded operating system has Linux, Windows CE, VxWorks, Nucleus, uC/OS-II and so on, uC/OS-II is one may transplant, the solidifiable, to be possible to cut out takes the lead the type real-time operating system, its peripheral complete set of products is also quite perfect, like products and so on uC/FS, uC/GUI strengthened the serviceability for its application, the relative other operating system says, the uC/OS-II normal operation only needs several or several dozens KB Flash space and the SRAM space, and its needs the authorized expense relatively is also low, unionTake LPC2214 as the core hardware platform, used uC/OS-II in here to take this equipment’s embedded operating system.
Has the above analysis to be possible to know, chooses the embedded platform which LPC2214 and uC/OS-II unify is one kind more economical, but practical method.
2 audio frequency decoding chip choice
LPC2214 and uC/OS-II unify the platform has the quite formidable handling ability, but in many application situations still obviously insufficient, in this article introduced in the application, the system needs to have the audio frequency to arrange the decoding function, the audio frequency arranges the decoding way to arrange the decoding and the hardware including the software arranges the decoding, if uses the software to arrange the decoding the way, to processor processing speed request generally above 50MIPS, but the LPC2214 processing speed only has about 70MIPS, if obviously selects this method, LPC2214 handling ability will receive the very big limit, therefore, used the special audio frequency processing chip to process the voice data to this platform isThe correct choice, here selects a section of high performance the audio frequency decoding chip–VS1003.
The VS1003 audio frequency decoding chip is the VS10XX series third generation product, is monolithic MP3/WMA/MIDI decoding which and ADPCM code chip Finnish VLSI Solution Oy Corporation produces, its interior contains a high performance, the low power loss DSP processing nucleus (VSDSP), a work memory, a piece may supply the user program use 5.5KB RAM, a serial SPI bus interface, high grade sampling frequency adjustable sampling DAC as well as 16 sampling ADC, VS1003 internal structure as shown in Figure 1.
3 VS1003 controlling agreement realization
VS1003 in carries on the data and the control information exchange through a work from the pattern SPI serial main line and the main engine, the voice data (SDI) transmits through the serial data connection, the control data (SCI) transmits through the serial control interface, the control data is always 16, through reads/writes the different register to realize to VS1003 the control.
The VS1003 SPI connection has two kind of working patterns: VS1002 new pattern and VS1001 compatibility mode. Establishes SM_SDINEW is 1, causes VS1003 to be in the VS1002 new pattern. When SMSDISHARED is 0, the control signal and the data signal’s transmission uses xCS and xDCS separately takes the synchronized signal, but when SMSDISHARED is 1, uses in common xCS to take the synchronized signal, establishes SM_SDINEW is 0, causes VS1003 to be in the VS1001 compatibility mode, this pattern only by xCS function synchronized signal.
Takes from machine the working pattern, VS1003 through holding wire DREQ instructed whether to permit the main engine transmission data, when DREQ is high, VS1003 at least may accept 32KB the SDI data or the SCI control command.
In here, by the VS1002 new pattern, and the SMSDISHARED establishment is 0 introduces the VS1003 communication protocol for the example realization. Figure 2 described the SDI work succession, it take xDCS as the synchronized signal, along with the clock signal DCLK change, the data in turn sends out according to the SCL_MODE establishment from the top digit or the low position.
SCI agreement including 1 control command byte, 1 address byte and 1 16 bit data character. Each time the read-write control may operate a register. Reads the order and writes the order respectively is 0×03 and 0×02, these two kind of control command’s work succession distinction like chart 3 and shown in Figure 4.
4 circuit designs
This design must realize finally the goal is one section has the man-machine contact surface and the data storage function labor controls grasps the equipment, operates VS1003 through the man-machine conversation contact surface transmission control command, realizes records the playback function.
4.1 hardware circuit design
VS1003 all data and the control command realize through the SPI bus interface, therefore realizes with the LPC2214 connection is quite simple, including 3 SPI data lines and 4 pilot wires, as shown in Figure 5.
4.2 software designs
The VS1003 control software design, is in the system transplanted the uC/OS-II operating system as well as under successfully the ZLGFS filing system’s condition carries on, in the concrete software design, first carries on the corresponding disposition to LPC2214 and the VS1003 control interface’s several function pin, then enables SPI and establishes its working pattern, hereafter, uses the uC/OS-II multi-duties the characteristic, establishes a special duty to use in realizing system’s record playback function, after this duty foundation finished, first completed to the VS1003 initialization work, then the duty entered in the waiting loop, the waiting system issued the corresponding control command, when this duty received the recording instruction, transferWhen the corresponding recording function function start sound recording function, and will record the document which the data reads in assigns, when receives the broadcast function command, the transfer broadcast function function, the broadcast assigns audio frequency document, when receives the interrupt instruction, will withdraw records the playback function, the duty returns to circulate in the waiting, this duty realizes the function to be as follows specifically:
5 summaries
Uses VS1003 to realize based on LPC2214 and the uC/OS- II embedded platform audio frequency arranges the decoding the function, the interface circuit is simple, the control procedure easy to compile, and the final audio frequency broadcast is clear, the nature, also once met certainly the question which in the concrete design some needs to pay attention, for example must succeed to VS1003 carries on the initialization, must understand in detail VS1003 results in the disposition succession request, what must pay attention specially, completes to the different register disposition, its waiting processing period differs from, if the waiting cycle is insufficient, will cause the disposition to be unable to complete normally.
