ESP32:7.DAC - 技术栈

硬件：ESP32-Devkit-V4 MODEL:ESP32-32U

库：ESP-IDF v5.4.1

系统：windows中的虚拟机 ubuntu 22.04

1.注意事项

分辨率限制：8 位（256 级），输出电压范围 0-3.3V，每步约 12.9 mV。
输出阻抗：DAC 输出阻抗较高，驱动能力弱，建议连接运放缓冲。
噪声性能：ESP32 DAC 噪声相对较高，不适用于高精度应用。
电源影响：输出电压精度受 VDD3P3_RTC 电源质量影响。
并发限制：
使用 dac_output_voltage()时，余弦波生成器自动禁用。
启用余弦波生成器时，dac_output_voltage()无效。
引脚复用：
GPIO 25 和 26 在启用 DAC 时不能用于其他功能（如 ADC）。
这两个引脚没有内部上拉/下拉电阻。

2. 校准建议

为提高精度，可考虑：

测量实际输出电压，建立查找表。
外部添加 RC 滤波器减少高频噪声。
使用外部运放提高驱动能力。

DAC API 相对简单，适合音频提示、简单波形生成、电压基准等应用场景

头文件

c 复制代码

#ifndef BSP_DAC_H_
#define BSP_DAC_H_

void dac_adc_monitor_init_task(void);

#endif

源文件

c 复制代码

#include "bsp_dac.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/dac_cosine.h"
#include "esp_adc/adc_oneshot.h"
#include "esp_check.h"

#if CONFIG_IDF_TARGET_ESP32
#define EXAMPLE_DAC_CHAN0_ADC_CHAN          ADC_CHANNEL_8   // GPIO25, same as DAC channel 0
#define EXAMPLE_DAC_CHAN1_ADC_CHAN          ADC_CHANNEL_9   // GPIO26, same as DAC channel 1
#define EXAMPLE_ADC_WIDTH                   ADC_WIDTH_BIT_12
#elif CONFIG_IDF_TARGET_ESP32S2
#define EXAMPLE_DAC_CHAN0_ADC_CHAN          ADC_CHANNEL_6   // GPIO17, same as DAC channel 0
#define EXAMPLE_DAC_CHAN1_ADC_CHAN          ADC_CHANNEL_7   // GPIO18, same as DAC channel 1
#define EXAMPLE_ADC_WIDTH                   ADC_WIDTH_BIT_13
#endif
#define EXAMPLE_ADC_ATTEN                   ADC_ATTEN_DB_12

static void adc_monitor_task(void *args)
{
    /* Set the ADC2 channels, these channels are connected to the DAC channels internally */
    adc_oneshot_unit_handle_t adc2_handle = (adc_oneshot_unit_handle_t)args;
    int chan0_val = 0;
    int chan1_val = 0;
    while (1) {
        /* Read the DAC output voltage */
        ESP_ERROR_CHECK(adc_oneshot_read(adc2_handle, EXAMPLE_DAC_CHAN0_ADC_CHAN, &chan0_val));
        ESP_ERROR_CHECK(adc_oneshot_read(adc2_handle, EXAMPLE_DAC_CHAN1_ADC_CHAN, &chan1_val));
        printf("DAC channel 0 value: %4d\tDAC channel 1 value: %4d\n", chan0_val, chan1_val);
        vTaskDelay(pdMS_TO_TICKS(100));
    }
}

void dac_adc_monitor_init_task(void)
{
    dac_cosine_handle_t chan0_handle;
    dac_cosine_handle_t chan1_handle;
    /* Normally two channels can only be configured to one frequency
     * But we can set force_set_freq bit to force update the frequency
     * The example here will produce cosine wave at 8 KHz on both channels */
    dac_cosine_config_t cos0_cfg = {
        .chan_id = DAC_CHAN_0,
        .freq_hz = 1000, // It will be covered by 8000 in the latter configuration
        .clk_src = DAC_COSINE_CLK_SRC_DEFAULT,
        .offset = 0,
        .phase = DAC_COSINE_PHASE_0,
        .atten = DAC_COSINE_ATTEN_DEFAULT,
        .flags.force_set_freq = false,
    };
    dac_cosine_config_t cos1_cfg = {
        .chan_id = DAC_CHAN_1,
        .freq_hz = 8000,
        .clk_src = DAC_COSINE_CLK_SRC_DEFAULT,
        .offset = 0,
        .phase = DAC_COSINE_PHASE_180,
        .atten = DAC_COSINE_ATTEN_DB_6,
        .flags.force_set_freq = true, // set true will allow to overwrite the frequency that set before
    };
    ESP_ERROR_CHECK(dac_cosine_new_channel(&cos0_cfg, &chan0_handle));
    ESP_ERROR_CHECK(dac_cosine_new_channel(&cos1_cfg, &chan1_handle));
    ESP_ERROR_CHECK(dac_cosine_start(chan0_handle));
    ESP_ERROR_CHECK(dac_cosine_start(chan1_handle));

    /* Set the ADC2 channels, these channels are connected to the DAC channels internally */
    adc_oneshot_unit_handle_t adc2_handle;
    adc_oneshot_unit_init_cfg_t adc_cfg = {
        .unit_id = ADC_UNIT_2,
        .ulp_mode = false,
    };
    ESP_ERROR_CHECK(adc_oneshot_new_unit(&adc_cfg, &adc2_handle));
    adc_oneshot_chan_cfg_t chan_cfg = {
        .atten = EXAMPLE_ADC_ATTEN,
        .bitwidth = ADC_BITWIDTH_DEFAULT,
    };
    ESP_ERROR_CHECK(adc_oneshot_config_channel(adc2_handle, EXAMPLE_DAC_CHAN0_ADC_CHAN, &chan_cfg));
    ESP_ERROR_CHECK(adc_oneshot_config_channel(adc2_handle, EXAMPLE_DAC_CHAN1_ADC_CHAN, &chan_cfg));
    xTaskCreate(adc_monitor_task, "adc_monitor_task", 4096, adc2_handle, 5, NULL);
}