adc: add comment for ADC sampling frequency

components/driver/esp32c3/adc.c

@@ -531,7 +531,7 @@ esp_err_t adc_digi_controller_config(const adc_digi_config_t *config)
     if (!s_adc_digi_ctx) {
         return ESP_ERR_INVALID_STATE;
     }
-    ADC_CHECK(config->sample_freq_hz <= 83333 && config->sample_freq_hz >= 610, "ADC sampling frequency out of range", ESP_ERR_INVALID_ARG);
+    ADC_CHECK(config->sample_freq_hz <= SOC_ADC_SAMPLE_FREQ_THRES_HIGH && config->sample_freq_hz >= SOC_ADC_SAMPLE_FREQ_THRES_LOW, "ADC sampling frequency out of range", ESP_ERR_INVALID_ARG);
 
     s_adc_digi_ctx->digi_controller_config.conv_limit_en = config->conv_limit_en;
     s_adc_digi_ctx->digi_controller_config.conv_limit_num = config->conv_limit_num;

components/hal/include/hal/adc_types.h

@@ -286,12 +286,11 @@ typedef struct {
                                                  If the number of measurements reaches `dma_eof_num`, then `dma_in_suc_eof` signal is generated in DMA.
                                                  Note: The converted data in the DMA in link buffer will be multiple of two bytes. */
 #elif CONFIG_IDF_TARGET_ESP32C3
-    uint32_t sample_freq_hz;  /*!< The expected ADC sampling frequency in Hz. Range: 610Hz ~ 83333Hz
-                                   Fs: sampling frequency;
-                                   Fd: digital controller frequency
-                                   interval: interval between 2 measurement trigger signal
+    uint32_t sample_freq_hz;  /*!< The expected ADC sampling frequency in Hz. Range: 611Hz ~ 83333Hz
                                    Fs = Fd / interval / 2
-                                   Range: the smallest interval should not be smaller than the ADC measurement period. The largest interval should not be larger than 4095. */
+                                   Fs: sampling frequency;
+                                   Fd: digital controller frequency, no larger than 5M for better performance
+                                   interval: interval between 2 measurement trigger signal, the smallest interval should not be smaller than the ADC measurement period, the largest interval should not be larger than 4095 */
 #endif
 } adc_digi_config_t;
 

components/soc/esp32c3/include/soc/soc_caps.h

@@ -102,21 +102,17 @@
 #define SOC_AES_SUPPORT_AES_256 (1)
 
 /*-------------------------- ADC CAPS -------------------------------*/
-#define SOC_ADC_PERIPH_NUM              (2)
-#define SOC_ADC_PATT_LEN_MAX            (16)
-#define SOC_ADC_CHANNEL_NUM(PERIPH_NUM) ((PERIPH_NUM==0)? 5 : 1)
-#define SOC_ADC_MAX_CHANNEL_NUM         (10)
-#define SOC_ADC_MAX_BITWIDTH            (12)
-#define SOC_ADC_DIGI_FILTER_NUM         (2)
-#define SOC_ADC_DIGI_MONITOR_NUM        (2)
-
-/**
- * Check if adc support digital controller (DMA) mode.
- * @value
- *      - 1 : support;
- *      - 0 : not support;
- */
-#define SOC_ADC_SUPPORT_DMA_MODE(PERIPH_NUM) 1
+#define SOC_ADC_PERIPH_NUM                      (2)
+#define SOC_ADC_PATT_LEN_MAX                    (16)
+#define SOC_ADC_CHANNEL_NUM(PERIPH_NUM)         ((PERIPH_NUM==0)? 5 : 1)
+#define SOC_ADC_MAX_CHANNEL_NUM                 (10)
+#define SOC_ADC_MAX_BITWIDTH                    (12)
+#define SOC_ADC_DIGI_FILTER_NUM                 (2)
+#define SOC_ADC_DIGI_MONITOR_NUM                (2)
+#define SOC_ADC_SUPPORT_DMA_MODE(PERIPH_NUM)    1
+//F_sample = F_digi_con / 2 / interval. F_digi_con = 5M for now. 30 <= interva <= 4095
+#define SOC_ADC_SAMPLE_FREQ_THRES_HIGH          83333
+#define SOC_ADC_SAMPLE_FREQ_THRES_LOW           611
 
 /*-------------------------- APB BACKUP DMA CAPS -------------------------------*/
 #define SOC_APB_BACKUP_DMA              (1)

examples/peripherals/adc/adc_dma/main/adc_dma_example_main.c

@@ -25,10 +25,12 @@ static void continuous_adc_init(uint16_t adc1_chan_mask, uint16_t adc2_chan_mask
     assert(ret == ESP_OK);
 
     adc_digi_pattern_table_t adc_pattern[10] = {0};
+
+    //Do not set the sampling frequency out of the range between `SOC_ADC_SAMPLE_FREQ_THRES_LOW` and `SOC_ADC_SAMPLE_FREQ_THRES_HIGH`
     adc_digi_config_t dig_cfg = {
         .conv_limit_en = 0,
         .conv_limit_num = 250,
-        .sample_freq_hz = 83333,
+        .sample_freq_hz = 620,
     };
 
     dig_cfg.adc_pattern_len = channel_num;