| /* ---------------------------------------------------------------------- |
| * Copyright (C) 2010-2012 ARM Limited. All rights reserved. |
| * |
| * $Date: 17. January 2013 |
| * $Revision: V1.4.0 |
| * |
| * Project: CMSIS DSP Library |
| * Title: arm_fir_example_f32.c |
| * |
| * Description: Example code demonstrating how an FIR filter can be used |
| * as a low pass filter. |
| * |
| * Target Processor: Cortex-M4/Cortex-M3 |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * - Neither the name of ARM LIMITED nor the names of its contributors |
| * may be used to endorse or promote products derived from this |
| * software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
| * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
| * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
| * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| * POSSIBILITY OF SUCH DAMAGE. |
| * -------------------------------------------------------------------- */ |
| |
| /** |
| * @ingroup groupExamples |
| */ |
| |
| /** |
| * @defgroup FIRLPF FIR Lowpass Filter Example |
| * |
| * \par Description: |
| * \par |
| * Removes high frequency signal components from the input using an FIR lowpass filter. |
| * The example demonstrates how to configure an FIR filter and then pass data through |
| * it in a block-by-block fashion. |
| * \image html FIRLPF_signalflow.gif |
| * |
| * \par Algorithm: |
| * \par |
| * The input signal is a sum of two sine waves: 1 kHz and 15 kHz. |
| * This is processed by an FIR lowpass filter with cutoff frequency 6 kHz. |
| * The lowpass filter eliminates the 15 kHz signal leaving only the 1 kHz sine wave at the output. |
| * \par |
| * The lowpass filter was designed using MATLAB with a sample rate of 48 kHz and |
| * a length of 29 points. |
| * The MATLAB code to generate the filter coefficients is shown below: |
| * <pre> |
| * h = fir1(28, 6/24); |
| * </pre> |
| * The first argument is the "order" of the filter and is always one less than the desired length. |
| * The second argument is the normalized cutoff frequency. This is in the range 0 (DC) to 1.0 (Nyquist). |
| * A 6 kHz cutoff with a Nyquist frequency of 24 kHz lies at a normalized frequency of 6/24 = 0.25. |
| * The CMSIS FIR filter function requires the coefficients to be in time reversed order. |
| * <pre> |
| * fliplr(h) |
| * </pre> |
| * The resulting filter coefficients and are shown below. |
| * Note that the filter is symmetric (a property of linear phase FIR filters) |
| * and the point of symmetry is sample 14. Thus the filter will have a delay of |
| * 14 samples for all frequencies. |
| * \par |
| * \image html FIRLPF_coeffs.gif |
| * \par |
| * The frequency response of the filter is shown next. |
| * The passband gain of the filter is 1.0 and it reaches 0.5 at the cutoff frequency 6 kHz. |
| * \par |
| * \image html FIRLPF_response.gif |
| * \par |
| * The input signal is shown below. |
| * The left hand side shows the signal in the time domain while the right hand side is a frequency domain representation. |
| * The two sine wave components can be clearly seen. |
| * \par |
| * \image html FIRLPF_input.gif |
| * \par |
| * The output of the filter is shown below. The 15 kHz component has been eliminated. |
| * \par |
| * \image html FIRLPF_output.gif |
| * |
| * \par Variables Description: |
| * \par |
| * \li \c testInput_f32_1kHz_15kHz points to the input data |
| * \li \c refOutput points to the reference output data |
| * \li \c testOutput points to the test output data |
| * \li \c firStateF32 points to state buffer |
| * \li \c firCoeffs32 points to coefficient buffer |
| * \li \c blockSize number of samples processed at a time |
| * \li \c numBlocks number of frames |
| * |
| * \par CMSIS DSP Software Library Functions Used: |
| * \par |
| * - arm_fir_init_f32() |
| * - arm_fir_f32() |
| * |
| * <b> Refer </b> |
| * \link arm_fir_example_f32.c \endlink |
| * |
| */ |
| |
| |
| /** \example arm_fir_example_f32.c |
| */ |
| |
| /* ---------------------------------------------------------------------- |
| ** Include Files |
| ** ------------------------------------------------------------------- */ |
| |
| #include "arm_math.h" |
| #include "math_helper.h" |
| |
| /* ---------------------------------------------------------------------- |
| ** Macro Defines |
| ** ------------------------------------------------------------------- */ |
| |
| #define TEST_LENGTH_SAMPLES 320 |
| #define SNR_THRESHOLD_F32 140.0f |
| #define BLOCK_SIZE 32 |
| #define NUM_TAPS 29 |
| |
| /* ------------------------------------------------------------------- |
| * The input signal and reference output (computed with MATLAB) |
| * are defined externally in arm_fir_lpf_data.c. |
| * ------------------------------------------------------------------- */ |
| |
| extern float32_t testInput_f32_1kHz_15kHz[TEST_LENGTH_SAMPLES]; |
| extern float32_t refOutput[TEST_LENGTH_SAMPLES]; |
| |
| /* ------------------------------------------------------------------- |
| * Declare Test output buffer |
| * ------------------------------------------------------------------- */ |
| |
| static float32_t testOutput[TEST_LENGTH_SAMPLES]; |
| |
| /* ------------------------------------------------------------------- |
| * Declare State buffer of size (numTaps + blockSize - 1) |
| * ------------------------------------------------------------------- */ |
| |
| static float32_t firStateF32[BLOCK_SIZE + NUM_TAPS - 1]; |
| |
| /* ---------------------------------------------------------------------- |
| ** FIR Coefficients buffer generated using fir1() MATLAB function. |
| ** fir1(28, 6/24) |
| ** ------------------------------------------------------------------- */ |
| |
| const float32_t firCoeffs32[NUM_TAPS] = { |
| -0.0018225230f, -0.0015879294f, +0.0000000000f, +0.0036977508f, +0.0080754303f, +0.0085302217f, -0.0000000000f, -0.0173976984f, |
| -0.0341458607f, -0.0333591565f, +0.0000000000f, +0.0676308395f, +0.1522061835f, +0.2229246956f, +0.2504960933f, +0.2229246956f, |
| +0.1522061835f, +0.0676308395f, +0.0000000000f, -0.0333591565f, -0.0341458607f, -0.0173976984f, -0.0000000000f, +0.0085302217f, |
| +0.0080754303f, +0.0036977508f, +0.0000000000f, -0.0015879294f, -0.0018225230f |
| }; |
| |
| /* ------------------------------------------------------------------ |
| * Global variables for FIR LPF Example |
| * ------------------------------------------------------------------- */ |
| |
| uint32_t blockSize = BLOCK_SIZE; |
| uint32_t numBlocks = TEST_LENGTH_SAMPLES/BLOCK_SIZE; |
| |
| float32_t snr; |
| |
| /* ---------------------------------------------------------------------- |
| * FIR LPF Example |
| * ------------------------------------------------------------------- */ |
| |
| int32_t main(void) |
| { |
| uint32_t i; |
| arm_fir_instance_f32 S; |
| arm_status status; |
| float32_t *inputF32, *outputF32; |
| |
| /* Initialize input and output buffer pointers */ |
| inputF32 = &testInput_f32_1kHz_15kHz[0]; |
| outputF32 = &testOutput[0]; |
| |
| /* Call FIR init function to initialize the instance structure. */ |
| arm_fir_init_f32(&S, NUM_TAPS, (float32_t *)&firCoeffs32[0], &firStateF32[0], blockSize); |
| |
| /* ---------------------------------------------------------------------- |
| ** Call the FIR process function for every blockSize samples |
| ** ------------------------------------------------------------------- */ |
| |
| for(i=0; i < numBlocks; i++) |
| { |
| arm_fir_f32(&S, inputF32 + (i * blockSize), outputF32 + (i * blockSize), blockSize); |
| } |
| |
| /* ---------------------------------------------------------------------- |
| ** Compare the generated output against the reference output computed |
| ** in MATLAB. |
| ** ------------------------------------------------------------------- */ |
| |
| snr = arm_snr_f32(&refOutput[0], &testOutput[0], TEST_LENGTH_SAMPLES); |
| |
| if (snr < SNR_THRESHOLD_F32) |
| { |
| status = ARM_MATH_TEST_FAILURE; |
| } |
| else |
| { |
| status = ARM_MATH_SUCCESS; |
| } |
| |
| /* ---------------------------------------------------------------------- |
| ** Loop here if the signal does not match the reference output. |
| ** ------------------------------------------------------------------- */ |
| |
| if ( status != ARM_MATH_SUCCESS) |
| { |
| while (1); |
| } |
| |
| while (1); /* main function does not return */ |
| } |
| |
| /** \endlink */ |