add some code

managed_components/espressif__esp-dsp/examples/iir/main/CMakeLists.txt

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+idf_component_register(SRCS "dsps_iir_main.c")

managed_components/espressif__esp-dsp/examples/iir/main/dsps_iir_main.c

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+// Copyright 2018-2019 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "esp_system.h"
+#include "driver/spi_master.h"
+#include "soc/gpio_struct.h"
+#include "driver/gpio.h"
+#include "driver/uart.h"
+#include "soc/uart_struct.h"
+#include <math.h>
+
+#include "esp_dsp.h"
+
+static const char *TAG = "main";
+
+// This example shows how to use iir filters from esp-dsp library
+
+#define N_SAMPLES 1024
+int N = N_SAMPLES;
+// Input test array
+__attribute__((aligned(16)))
+float d[N_SAMPLES];
+// output array
+__attribute__((aligned(16)))
+float y[N_SAMPLES];
+__attribute__((aligned(16)))
+float y_cf[N_SAMPLES * 2];
+
+// Function shows result of IIR filter
+void ShowIIRfilter(float freq, float qFactor)
+{
+    esp_err_t ret = ESP_OK;
+    float coeffs_lpf[5];
+    float w_lpf[5] = {0, 0};
+    // Calculate iir filter coefficients
+    ret = dsps_biquad_gen_lpf_f32(coeffs_lpf, freq, qFactor);
+    if (ret  != ESP_OK) {
+        ESP_LOGE(TAG, "Operation error = %i", ret);
+        return;
+    }
+    // Process input signal
+    unsigned int start_b = dsp_get_cpu_cycle_count();
+    ret = dsps_biquad_f32(d, y, N, coeffs_lpf, w_lpf);
+    unsigned int end_b = dsp_get_cpu_cycle_count();
+    if (ret  != ESP_OK) {
+        ESP_LOGE(TAG, "Operation error = %i", ret);
+        return;
+    }
+
+    // Show result as a plot
+    ESP_LOGI(TAG, "Impulse response of IIR filter with F=%f, qFactor=%f", freq, qFactor);
+    dsps_view(y, 128, 64, 10,  -1, 1, '-');
+
+    // Show result as frequency responce on the plot
+    for (int i = 0 ; i < N ; i++) {
+        y_cf[i * 2 + 0] = y[i];
+        y_cf[i * 2 + 1] = 0;
+    }
+
+    // We making FFT transform
+    dsps_fft2r_fc32_ansi(y_cf, N);
+    // Bit reverse
+    dsps_bit_rev_fc32_ansi(y_cf, N);
+    // Calculating power of spectrum in dB
+    for (int i = 0 ; i < N / 2 ; i++) {
+        y_cf[i] = 10 * log10f((y_cf[i * 2 + 0] * y_cf[i * 2 + 0] + y_cf[i * 2 + 1] * y_cf[i * 2 + 1]) / N);
+    }
+    // Show power spectrum in 64x10 window from -100 to 0 dB from 0..N/2 samples
+    dsps_view(y_cf, N / 2, 64, 10,  -100, 0, '-');
+    ESP_LOGI(TAG, "IIR for %i samples take %i cycles", N, end_b - start_b);
+}
+
+void app_main()
+{
+    esp_err_t ret;
+    ESP_LOGI(TAG, "Start Example.");
+    // If user don't care about buffer allocation, the defalt
+    // initialization could be used as shown here:
+    ret = dsps_fft2r_init_fc32(NULL, CONFIG_DSP_MAX_FFT_SIZE);
+    if (ret  != ESP_OK) {
+        ESP_LOGE(TAG, "Not possible to initialize FFT. Error = %i", ret);
+        return;
+    }
+
+    // Initialize input signal
+    // Generate d function as input signal
+    dsps_d_gen_f32(d, N, 0);
+
+    // Show filter with Q factor 1
+    ShowIIRfilter(0.1, 1);
+    // Show filter with Q factor 10
+    ShowIIRfilter(0.1, 10);
+
+    ESP_LOGI(TAG, "End Example.");
+}

managed_components/espressif__esp-dsp/examples/iir/main/idf_component.yml

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+dependencies:
+  espressif/esp-dsp:
+    override_path: "../../../"
+    version: "*"