C674x DSP的库函数调用.doc-资料库

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C674x DSPLIB From Texas Instruments Embedded Processors Wiki Contents [hide]  1 Introduction o o o o o o 1.1 Installation 1.2 Usage 1.3 Performance 1.4 Interruptibility 1.5 File Structure 1.6 Known Issues  2 Single-Precision Kernels o o o o o o o o o o o o o o o o o o o o o o 2.1 DSPF_sp_autocor (Autocorrelation) 2.2 DSPF_sp_biquad (Biquad Filter) 2.3 DSPF_sp_blk_move (Block Copy) 2.4 DSPF_sp_convol (Convolution) 2.5 DSPF_sp_dotp_cplx (Complex Dot Product) 2.6 DSPF_sp_dotprod (Dot Product) 2.7 DSPF_sp_fftSPxSP (Mixed Radix Forward FFT with Bit Reversal) 2.8 DSPF_sp_fir_cplx (Complex FIR Filter) 2.9 DSPF_sp_fir_gen (FIR Filter) 2.10 DSPF_sp_fir_r2 (FIR Filter Alternate Implementation) 2.11 DSPF_sp_fircirc (FIR Filter with Circular Input) 2.12 DSPF_sp_ifftSPxSP (Mixed Radix Inverse FFT with Bit Reversal) 2.13 DSPF_sp_iir (IIR Filter) 2.14 DSPF_sp_iirlat (Lattice IIR Filter) 2.15 DSPF_sp_lms (LMS Adaptive Filter) 2.16 DSPF_sp_mat_mul (Matrix Multiply) 2.17 DSPF_sp_mat_mul_cplx (Complex Matrix Multiply) 2.18 DSPF_sp_mat_trans (Matrix Transpose) 2.19 DSPF_sp_maxidx (Maximum Index) 2.20 DSPF_sp_maxval (Maximum Value) 2.21 DSPF_sp_minerr (VSELP Vocoder Codebook Search) 2.22 DSPF_sp_minval (Minimum Value)

o o o o 2.23 DSPF_sp_vecmul (Vector Multiplication) 2.24 DSPF_sp_vecrecip (Vector Reciprocal) 2.25 DSPF_sp_vecsum_sq (Vector Sum of Squares) 2.26 DSPF_sp_w_vec (Vector Weighted Sum)  3 Miscellaneous Kernels o o o o o 3.1 DSPF_blk_eswap16 (16-bit Endianness Swap) 3.2 DSPF_blk_eswap32 (32-bit Endianness Swap) 3.3 DSPF_blk_eswap64 (64-bit Endianness Swap) 3.4 DSPF_fltoq15 (Float to Q.15 Conversion) 3.5 DSPF_q15tofl (Q.15 to Float Conversion) Introduction The C674x DSPLIB is a partial C port of the C67x DSPLIB. The pre-existing library was written in assembly and suffered from bugs and undocumented code requirements. The new release is intended to correct these problems and provide a more coherent and maintainable code base. Each kernel includes source for a "natural" C and optimized C kernel, as well as a sample project demonstrating its use. Please note that the C674x DSPLIB is a floating point library. For fixed point computation, the C674x core is fully compatible with the C64x+ DSPLIB. Installation Visit the C674x DSPLIB web page on ti.com: Download the Windows Installer sprc900.zip Download the Linux Installer sprc906.gz (tar -xzf sprc906.gz to uncompress) Usage The DSPLIB contains a pre-compiled library file and C header. To use the DSPLIB, simply include the library file, dsplib674x.lib, in your project and include the header file in your C source: #include "dsplib674x.h"

Note that the compiler must know to look for header files in your DSPLIB installation folder. This is easily achieved with a compiler directive similar to -i"C:\CCStudio_v3.3\c674x\dsplib_v12". The DSPLIB can be re-built using the dsplib674x.pjt CCS project file. This will pull in any modifications that you have made to the individual kernel source files. Performance The performance of the optimized C kernels should be better than or comparable to the performance of their ASM counterparts. Certain kernels may retain their older assembly implementation if the C version can't match its efficiency. Also, some FFT kernels have received new and improved assembly implementations due to their performance-critical nature. Detailed comparisons of the kernels' C674x and C67x implementations are listed in a development notes spreadsheet. This file is included in the docs folder of the C674x DSPLIB installation. To benchmark the DSPLIB kernels, TI recommends the use of the C674x Cycle Accurate Simulator, which is included in Code Composer Studio 3.3 with Service Release 12 or later. After loading CCS, select Profile->Clock->Enable. This will allow the kernel demonstration apps to accurately display cycle counts. Otherwise, the cycle counts will likely be incorrectly reported as zero. Interruptibility All code in the C674x DSPLIB is interrupt tolerant. Many of the C language kernels are fully interruptible. To check whether a kernel is interruptible, follow this procedure: 1. Open and build the kernel's demonstration project in the src/DSPF_ folder in CCS. 2. If the project does not include the source file DSPF_.c, it is an ASM language kernel and is not interruptible. 3. If the project does include the source file DSPF_.c, building the project created a file named DSPF_.asm. Open this file. 4. If the file DSPF_.asm contains a SPLOOP instruction, the kernel is interruptible. Otherwise, the kernel is not interruptible.

If a C language kernel is not interruptible, it may be possible to sacrifice some performance to gain interruptibility. One method is to use the -ms0 (or --opt_for_space) compiler directive. This will encourage the compiler to use the SPLOOP opcode. In the top-level DSPLIB project, you can apply this directive to a single source file (and not the entire library) by right clicking the file in the project browser and selecting "File Specific Options..." from the drop-down menu. File Structure In addition to the top-level library and project files, The DSPLIB installation provides several source files for each kernel. Each file is located in the src/DSPF_ folder within the DSPLIB installation. Certain files may only be present for C or ASM language kernels. DSPF_.c DSPF_.asm DSPF_.h DSPF__cn.c DSPF__cn.h DSPF__opt.c DSPF__d.c C kernels only! Optimized C source for the kernel. This code is used to build the library. ASM kernels only! Optimized ASM source for the kernel. This code is used to build the library. Note: building the demo app for a C kernel may create a file with this name. C header for kernel. Included in the library's top-level header file. Natural C source for the kernel. This code is functionally equivalent to the optimized C source, but it is written to maximize clarity rather than performance. It is not included in the library itself. C header for natural C implementation of kernel. ASM kernels only! Optimized C source for the kernel. This code is provided as an alternative implementation and is not included in the library file. Demonstration C source for the kernel. The demonstration app shows a typical use case for the kernel. It calls the optimized C and natural C implementations to compare results and efficiency. Note: the cycle

DSPF__legacy.asm DSPF_.pjt link.cmd counts will only return non-zero values when this code is run in Code Composer Studio with the profiler enabled. Assembly source for the same kernel from the older C67x DSPLIB. This code is provided purely for comparison purposes within the demonstration app and is not included in the library file. Some C67x assembly kernels have bugs that cause them to return incorrect results. In rare cases, they may even crash the DSP. In this case, the legacy kernel will not be called in the demonstration app. If this file is not present for a particular kernel, the legacy ASM code is used in the library and can be found in DSPF_.asm. Code Composer Studio (CCS) project file for the demonstration app. This file is used to build the demonstration application in CCS. Linker command file for demonstration app project. Used to build demonstration app. Each demonstration app also makes use of a common source file that is used to compare output data from the various implementations of the DSPLIB kernel. This file, DSPF_util.c, is located in the src/DSPF_util folder in the DSPLIB installation. This file is not used by the actual library file itself. Known Issues Please refer to this topic. Single-Precision Kernels DSPF_sp_autocor (Autocorrelation) The DSPF_sp_autocor kernel performs autocorrelation on input array x. The result is stored in output array r.

Function Parameters void DSPF_sp_autocor(float *restrict r, float *restrict x, const int nx, const int nr) r x nx nr Pointer to output array. Must have nr elements. Pointer to input array. Must have nx + nr elements with nr 0-value elements at the beginning. Must be double word aligned. Length of input array. Must be an even number. Must be greater than or equal to nr. Length of autocorrelation sequence to calculate. Must be divisible by 4 and greater than 0. DSPF_sp_biquad (Biquad Filter) The DSPF_sp_biquad kernel performs biquad filtering on input array x using coefficient arrays a and b. The result is stored in output array y. A biquad filter is defined as an IIR filter with three (3) forward coefficients and two (2) feedback coefficients. The basic biquad transfer function can be expressed as:

H(z)=\frac{b_0 z + b_1 z^{-1} + b_2 z^{-2}}{1 - a_1 z^{-1} - a_2
z^{-2}}

(TODO: biquad diagram?) This kernel uses "delay" coefficients to simplify calculations. The delay coefficients are defined as follows:

delay[0] = b_1 x[n-1] + b_2 x[i-2] - a_1 y[i-1] - a_2 y[i-2]

delay[1] = b_2 x[i-1] - a_2 y[i-1]

The delay coefficients must be pre-calculated before calling the DSPF_sp_biquad kernel. Function Parameters void DSPF_sp_biquad(float *restrict x, float *b, float *a, float *delay, float *restrict y, const int n) x b a Pointer to input array. Must be length n. Pointer to forward coefficient array. Elements are (in order) b0, b1, and b2 in the biquad equation. Must be length 3. Pointer to feedback coefficient array. Elements

are (in order) a0, a1, and a2 in the biquad equation; a0 is not used. Must be an length 3. Pointer to delay coefficient array. The delay coefficients must be pre-calculated for the first output sample according to the above equations. The delay coefficients are overwritten by the kernel when it returns. The array must be length 2. Pointer to output array. Must be length n. Length of input and output arrays. Must be an even number. delay y n DSPF_sp_blk_move (Block Copy) The DSPF_sp_blk_move kernel copies a specified number of data words from input array x to output array y. Function Parameters void DSPF_sp_blk_move(const float * x, float *restrict y, const int n) x y n Pointer to input array. Must have n elements. Must be double word aligned. Pointer to output array. Must have n elements. Must be double word aligned. Length of input and output arrays. Must be an even number and greater than 0. DSPF_sp_convol (Convolution) The DSPF_sp_convol kernel convolves input array x with coefficient array h. The result is stored in output array y. Function Parameters void DSPF_sp_convol(const float *x, const float *h, float *restrict y, const short nh, const short ny) Pointer to input array. Must have ny + nh - 1 elements. Typically contains nh - 1 zero values at the beginning and end of the array. Must be double word aligned. Pointer to coefficient array. Must have nh elements. x h

y nh ny Pointer to output array. Must have ny elements. Must be double word aligned. Length of coefficient array. Must be an even number and greater than 0. Length of input and output arrays. Must be an even number and greater than 0. DSPF_sp_dotp_cplx (Complex Dot Product) The DSPF_sp_dotp_cplx kernel performs a dot product on two complex input arrays. The real and imaginary portions of the result are stored to separate output words. Function Parameters void DSPF_sp_dotp_cplx(const float * x, const float * y, int n, float * restrict re, float * restrict im) Pointer to first complex input array. Real and imaginary elements are respectively stored at even and odd index locations. Must have n * 2 elements. Must be double word aligned. Pointer to second complex input array. Real and imaginary elements are respectively stored at even and odd index locations. Must have n * 2 elements. Must be double word aligned. Number of complex values in input arrays. The length of each array is actually 2 * n. Must be an even number and greater than 0. Pointer real output word. Typically the address of a float variable. Pointer imaginary output word. Typically the address of a float variable. x y n re im DSPF_sp_dotprod (Dot Product) The DSPF_sp_dotprod kernel performs a dot product on two input arrays and returns the result. Function float DSPF_sp_dotprod(const float * x, const float * y, const int n)

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