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esp32开发与应用（边采样边播放音频）

news 2026/7/25 1:58:23

前面说到了音频的播放，一般采用i2s的格式，也就是bclk、lrclk、sda。今天来学一下麦克风。如果是播放音乐，没有麦克风也是可以的。但很多时候，我们还是有麦克风采样、录制的需求。所以这个时候，就要学一下麦克风采样。

1、麦克风接口

一般mic有两种接口，一种是pdm接口，也就是只有clk和data。还有一种就是i2s接口，这种就和之前的音乐播放一样的接口，即3个pin，lrclk、bclk和sda。

2、管脚分配

如果是mic，一般走4和5；如果是i2s，一般走26、25、22。

3、电压分配

3.3v即可。

4、芯片选型

这次采用的麦克风mic采样芯片，和前面一篇文章其实是一块板子，使用的芯片是lm2718。

5、示例代码

考虑到之前学习过音频播放，这里采用的方式是一边采样、一边播放的方式。这样既可以巩固原来的知识点，又可以学习到新的mic采样知识。整个就是一个扩音器的效果。

#include <stdint.h> #include <stdlib.h> #include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "esp_log.h" #include "driver/i2s_std.h" #include "driver/i2s_pdm.h" static const char *TAG = "MIC_LOOPBACK"; #define SAMPLE_RATE 16000 // ---- Mic (PDM RX) pins ---- #define PDM_CLK_GPIO GPIO_NUM_4 #define PDM_DATA_GPIO GPIO_NUM_5 // ---- Speaker (I2S STD TX, NS4168) pins ---- #define I2S_BCLK GPIO_NUM_26 #define I2S_WS GPIO_NUM_25 #define I2S_DOUT GPIO_NUM_22 #define READ_CHUNK_SAMPLES 512 // ~32ms per chunk @16kHz, controls latency static i2s_chan_handle_t rx_chan = NULL; // mic static i2s_chan_handle_t tx_chan = NULL; // speaker // ---------- Mic: PDM RX on I2S_NUM_0 ---------- static void mic_init(void) { i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_0, I2S_ROLE_MASTER); ESP_ERROR_CHECK(i2s_new_channel(&chan_cfg, NULL, &rx_chan)); i2s_pdm_rx_config_t pdm_rx_cfg = { .clk_cfg = I2S_PDM_RX_CLK_DEFAULT_CONFIG(SAMPLE_RATE), .slot_cfg = I2S_PDM_RX_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO), .gpio_cfg = { .clk = PDM_CLK_GPIO, .din = PDM_DATA_GPIO, .invert_flags = { .clk_inv = false }, }, }; pdm_rx_cfg.slot_cfg.slot_mask = I2S_PDM_SLOT_LEFT; // try _RIGHT if silent/noisy ESP_ERROR_CHECK(i2s_channel_init_pdm_rx_mode(rx_chan, &pdm_rx_cfg)); ESP_ERROR_CHECK(i2s_channel_enable(rx_chan)); ESP_LOGI(TAG, "Mic (PDM RX) ready on I2S_NUM_0, CLK=%d DATA=%d", PDM_CLK_GPIO, PDM_DATA_GPIO); } // ---------- Speaker: standard I2S TX on I2S_NUM_1 (same as your NS4168 code) ---------- static void speaker_init(void) { i2s_chan_config_t chan_cfg = I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_1, I2S_ROLE_MASTER); ESP_ERROR_CHECK(i2s_new_channel(&chan_cfg, &tx_chan, NULL)); i2s_std_config_t std_cfg = { .clk_cfg = I2S_STD_CLK_DEFAULT_CONFIG(SAMPLE_RATE), .slot_cfg = I2S_STD_PHILIPS_SLOT_DEFAULT_CONFIG(I2S_DATA_BIT_WIDTH_16BIT, I2S_SLOT_MODE_MONO), .gpio_cfg = { .mclk = I2S_GPIO_UNUSED, .bclk = I2S_BCLK, .ws = I2S_WS, .dout = I2S_DOUT, .din = I2S_GPIO_UNUSED, }, }; ESP_ERROR_CHECK(i2s_channel_init_std_mode(tx_chan, &std_cfg)); ESP_ERROR_CHECK(i2s_channel_enable(tx_chan)); ESP_LOGI(TAG, "Speaker (I2S STD TX) ready on I2S_NUM_1, BCLK=%d WS=%d DOUT=%d", I2S_BCLK, I2S_WS, I2S_DOUT); } // ---------- Loop: read from mic, write straight to speaker ---------- static void loopback_task(void *arg) { int16_t *buf = malloc(READ_CHUNK_SAMPLES * sizeof(int16_t)); if (!buf) { ESP_LOGE(TAG, "malloc failed"); vTaskDelete(NULL); return; } // Optional software gain: raw PDM mic level is often quiet. // Adjust or set to 1.0f if it clips/distorts. const float GAIN = 4.0f; while (1) { size_t bytes_read = 0; esp_err_t ret = i2s_channel_read(rx_chan, buf, READ_CHUNK_SAMPLES * sizeof(int16_t), &bytes_read, portMAX_DELAY); if (ret != ESP_OK || bytes_read == 0) { continue; } int samples = bytes_read / sizeof(int16_t); for (int i = 0; i < samples; i++) { int32_t v = (int32_t)(buf[i] * GAIN); if (v > INT16_MAX) v = INT16_MAX; if (v < INT16_MIN) v = INT16_MIN; buf[i] = (int16_t)v; } size_t bytes_written = 0; ESP_ERROR_CHECK( i2s_channel_write(tx_chan, buf, bytes_read, &bytes_written, portMAX_DELAY) ); } free(buf); vTaskDelete(NULL); } void app_main(void) { ESP_LOGI(TAG, "Mic -> Speaker realtime loopback starting"); mic_init(); speaker_init(); xTaskCreate(loopback_task, "loopback_task", 4096, NULL, 5, NULL); }