Abstract: This article introduced one kind based on the TMS320VC5416 multi-channel acceleration gathering and processing system’s design method. This system uses AD73360 to take front end the data acquisition, through DSP McBSP and the AD73360 cascade, may realize multi-channel simulation acceleration signal real-time gathering and processing.< ?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />
Key word: TMS320VC5416; AD73360; Acceleration; Data processing
Introduction
The multi-channel acceleration gathering system is playing the very important role in the platform inertial guidance system. In the early product, the control and the processing core use Feng ·nuo the clothes graceful bus structure the microprocessor, because its instruction execute speed is slow, designs a high performance real-time gathering and the processing system appears quite difficult. This article introduced one kind uses TMS320V C5416(DSP) to take the processor, gathers the system design method with 16 high accuracy AD73360 as the ADC multi-channel accelerations.
System hardware design
The system by a/D switching circuit, DSP and the peripheral circuit and the communication interface circuit is composed, as shown in Figure 1.
A/D switching circuit design
AD73360 synopsis
The AD73360 working pattern controls is convenient, when after the component adds the electricity, DSP or writes I/O through XF the way to select patches or strips of land as worth saving for seed AD73360 the SE pin to set for the high level, this time AD73360 is on answers by telegram the bit status, output synchronization frame signal SDOFS, when uses Figure 3 connection, may read in the control word through the DSP McBSP serial port to AD73360. AD73360 controls by 8 registers, the control word word length is 16.
When uses AD73360 carries on the circuit design, may directly with the unipolarity input mode, may also adopt the differential motion input mode to meet monolithic AD73360 three channel switches. However when uses the AD73360 component materials for internal reference voltage carries on the direct-current bias to the analog input front end, should better use the high input impedance the operational amplifier to carry on the isolation.
Acceleration signal pretreatment circuit design
The acceleration signal pretreatment electric circuit mainly carries on the sample, the direct-current bias and anti-aliasing filter processing to the input multi-channel acceleration signal, concrete electric circuit as shown in Figure 2.
Before directing current the bias, first uses precision resistor network R1 and R2 carries on the sample to the acceleration signal. To increase a/D conversion accuracy as far as possible, reduces the circuit wafer the volume, the system uses AD73360 internal reference voltage REFOUT to make the direct-current bias. Before delivering operational amplifier OP2 carries on the direct-current bias, uses operational amplifier OP1 to carry on the isolation, guarantees ADC the REFOUT post input, the output current, thus guarantees the ADC internal precise potential source voltage constant and the high A/D conversion accuracy. Finally, composes the RC network after R5 and C1, after anti-mixes the repeat filter, delivers AD73360 to carry on a/D transformation.
AD73360 and TMS320VC5416 connection design
The AD73360 internal integration has synchronized serial port SPI, through then may compose a multichannel synchro data gathering system with the DSP McBSP simple connection. AD73360 reset signal /RESET, selects patches or strips of land as worth saving for seed signal SE separately provides by DSP component’s /RESET and the XF pin through a rise along the double D trigger, like this may guarantee that AD73360 the reset signal, selects patches or strips of land as worth saving for seed the signal and DMCLK maintains a synchronization, in order to avoid has the read-write to be wrong. The McBSP input/outputs the clock to provide by AD73360, namely DSP synchronized cushion serial port work in external clock pattern. Through many piece of AD73360 cascades, most may realize 48 group synchronized gathering system (to see Figure 3). The system after receiving the master control monolithic integrated circuit’s start command, sets at XF for the high level, AD73360 is on answers by telegram the bit status, DSP writes the control word according to the order in all AD73360, finally starts A/D to transform, the system starts to the acceleration signal to carry on gathering.
DSP peripheral circuit and communication interface circuit design
DSP peripheral circuit including outside clock, power source, replacement as well as piece program memory electric circuit. The system uses the external clock pattern, the power source and the reset circuit uses TI Corporation special-purpose chip TPS767D301 and TPS3707-33. Because TMS320VC5416 not internal Flash, therefore the system uses AM29LV200B to take the program memory, this chip is 16 Flash memories. On after system electricity, the DSP internal vectoring procedure loads the AM29LV200B in working routine to internal SRAM, raises the program execution efficiency.
System communication electric circuit including parallel correspondence and serial communication two parts, because the master control monolithic integrated circuit uses the 5V logic, therefore the parallel correspondence’s handshake signal and the data line must use SN74LV245B to carry on the level isolation, simultaneously the data bus needs SN74LV373 to carry on the lock to save. If the parallel correspondence’s handshake signal uses the I/O read-write the way to realize, the data transmission efficiency will reduce many, therefore the system will define McBSP2 as the general I/O mouth, will come and the master control monolithic integrated circuit handshake with McBSP2, thus the reduced hardware expenses, will simultaneously raise the data transmission speed.
TMS320VC5416 internal non-UART port, must realize with the master control monolithic integrated circuit’s serial data correspondence, this system uses ST16C650< ?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />
In order to compile the modularity strongly, to carry out the efficiency high DSP procedure, this system selects the method which in the performance history the assembly language and the C language unify to carry on the software development. With the C language write program main body, carries on the hardware interface programming with the assembly language.
System software implementation as shown in Figure 4, left figure primarily procedure flow, figure to the right for interrupt routine flow. After the system adds the electricity, first to McBSP, AD73360, DMA and the string/and corresponds the connection and so on to carry on the initialization, then the waiting master control monolithic integrated circuit’s start command, after receiving the start command, starts to carry on the multi-channel acceleration signals gathering and processing, and after linear revision and filter’s acceleration information real-time transmission for master control monolithic integrated circuit.
Interrupt response procedure including timer interrupt routine, DMA interrupt routine and data transmission request interrupt routine. After the system opens the interrupt, once receives the start command, then starts AD73360, simultaneously the timer starts to time; After AD73360 will transform the separate acceleration information delivers DMA directly after McBSP0, and classifies installs to each RAM sector, when DMA assigns after the block data buffer fills, DSP responds the DMA interrupt, carries on the linear revision and the digital filtering to the acceleration information; If master control computer data request interrupt production, DSP through and mouth, serial port to master control computer transmission acceleration information and space position information; If the timer has the interrupt, DSP sets at switch variable T is 1. After interrupt returns, continues to carry on acceleration information processing, and judges switch variable T the condition, decided whether to give the control signal.
Because is more difficult in the ground simulation three dimensional acceleration input, in the data acquisition experiment, selects three group 100Hz sinusoidal signal to take the analog input, carries on the sampling with the 1kHz sampling rate. The gathering system scope and the phase uniformity are good, needs to further examine its gathering precision in the practical application.
Carry on the acceleration gathering system design using AD73360 and TMS320V C5416 to pay attention to the following several questions: Because the DSP system has the low power loss, the double power source and the high velocity performance, when design must consider the chip pin the external connection way and the craft characteristic; The AD73360 simulation power source and the digital power source must isolate; Between DSP and AD73360 connection when wiring must pay attention to the antijamming, when the necessity may serially connect 10 about in the serial data line the resistances; When uses AD73360 to provide the reference voltage which makes the direct-current bias, should better first use the operational amplifier isolation.
