adc: no longer support adc2 oneshot mode on esp32c3

Due to HW limitation, we don't support this anymore. On c3, ADC2 under oneshot mode is not stable.

However, you can enable CONFIG_ADC_ONESHOT_FORCE_USE_ADC2_ON_C3 to force use
ADC2.

Refer to errata to know more details:
https://www.espressif.com/sites/default/files/documentation/esp32-c3_errata_en.pdf

components/driver/Kconfig

@@ -30,6 +30,17 @@ menu "Driver configurations"
                 If you stick to this, you can enable this option to force use ADC2 under above conditions.
                 For more details, you can search for errata on espressif website.
 
+        config ADC_ONESHOT_FORCE_USE_ADC2_ON_C3
+            depends on IDF_TARGET_ESP32C3
+            bool "Force use ADC2 oneshot mode on ESP32C3"
+            default n
+            help
+                On ESP32C3, ADC2 Digital Controller is not stable. Therefore,
+                ADC2 oneshot mode is not suggested on ESP32C3
+
+                If you stick to this, you can enable this option to force use ADC2 under above conditions.
+                For more details, you can search for errata on espressif website.
+
     endmenu  # ADC Configuration
 
     menu "MCPWM configuration"

components/driver/adc.c

@@ -744,6 +744,11 @@ esp_err_t adc2_config_channel_atten(adc2_channel_t channel, adc_atten_t atten)
 
 esp_err_t adc2_get_raw(adc2_channel_t channel, adc_bits_width_t width_bit, int *raw_out)
 {
+#if !CONFIG_ADC_ONESHOT_FORCE_USE_ADC2_ON_C3
+    ESP_LOGE(ADC_TAG, "ADC2 is no longer supported, please use ADC1. Search for errata on espressif website for more details. You can enable ADC_ONESHOT_FORCE_USE_ADC2_ON_C3 to force use ADC2");
+    ESP_RETURN_ON_FALSE(SOC_ADC_DIG_SUPPORTED_UNIT(ADC_UNIT_2), ESP_ERR_INVALID_ARG, ADC_TAG, "adc unit not supported");
+#endif
+
     //On ESP32C3, the data width is always 12-bits.
     if (width_bit != ADC_WIDTH_BIT_12) {
         return ESP_ERR_INVALID_ARG;

components/driver/test/test_adc.c

@@ -290,6 +290,9 @@ TEST_CASE("test_adc_single", "[adc][ignore][manual]")
 /********************************************************************************
  *      ADC Speed Related Tests
  ********************************************************************************/
+//ESP32C3 ADC2 oneshot mode is not supported anymore
+#define ADC_TEST_ONESHOT_HIGH_LOW_TEST_ADC2    ((SOC_ADC_PERIPH_NUM >= 2) && !CONFIG_IDF_TARGET_ESP32C3)
+
 #ifdef CONFIG_IDF_TARGET_ESP32
 #define CPU_FREQ_MHZ                    CONFIG_ESP32_DEFAULT_CPU_FREQ_MHZ
 #elif CONFIG_IDF_TARGET_ESP32S2
@@ -374,26 +377,34 @@ TEST_CASE("test_adc_single_cali_time", "[adc][ignore][manual]")
 {
     ESP_LOGI(TAG, "CPU FREQ is %dMHz", CPU_FREQ_MHZ);
     uint32_t adc1_time_record[4][TIMES_PER_ATTEN] = {};
-    uint32_t adc2_time_record[4][TIMES_PER_ATTEN] = {};
     int adc1_raw = 0;
-    int adc2_raw = 0;
 
     //atten0 ~ atten3
     for (int i = 0; i < 4; i++) {
         ESP_LOGI(TAG, "----------------atten%d----------------", i);
         adc_single_cali_init(ADC_UNIT_1, ADC1_CALI_TEST_CHAN0, i);
+
+        for (int j = 0; j < TIMES_PER_ATTEN; j++) {
+            adc1_raw = adc1_get_raw(ADC1_CALI_TEST_CHAN0);
+            adc1_time_record[i][j] = get_cali_time_in_ccount(adc1_raw, &adc1_chars);
+            IDF_LOG_PERFORMANCE("ADC1 Cali time", "%d us", (int)GET_US_BY_CCOUNT(adc1_time_record[i][j]));
+        }
+    }
+
+#if ADC_TEST_ONESHOT_HIGH_LOW_TEST_ADC2
+    int adc2_raw = 0;
+    uint32_t adc2_time_record[4][TIMES_PER_ATTEN] = {};
+
+    //atten0 ~ atten3
+    for (int i = 0; i < 4; i++) {
+        ESP_LOGI(TAG, "----------------atten%d----------------", i);
         adc_single_cali_init(ADC_UNIT_2, ADC2_CALI_TEST_CHAN0, i);
 
         for (int j = 0; j < TIMES_PER_ATTEN; j++) {
-
-            adc1_raw = adc1_get_raw(ADC1_CALI_TEST_CHAN0);
             TEST_ESP_OK(adc2_get_raw(ADC2_CALI_TEST_CHAN0, ADC_WIDTH_BIT_DEFAULT, &adc2_raw));
-
-            adc1_time_record[i][j] = get_cali_time_in_ccount(adc1_raw, &adc1_chars);
             adc2_time_record[i][j] = get_cali_time_in_ccount(adc2_raw, &adc2_chars);
-
-            IDF_LOG_PERFORMANCE("ADC1 Cali time", "%d us", (int)GET_US_BY_CCOUNT(adc1_time_record[i][j]));
             IDF_LOG_PERFORMANCE("ADC2 Cali time", "%d us", (int)GET_US_BY_CCOUNT(adc2_time_record[i][j]));
         }
     }
+#endif  //#if ADC_TEST_ONESHOT_HIGH_LOW_TEST_ADC2
 }

docs/en/api-reference/peripherals/adc.rst

@@ -130,6 +130,8 @@ ADC Limitations
 
     .. only:: esp32c3
 
+        - ADC2 oneshot mode is no longer supported, due to hardware limitation. The results are not stable. This issue can be found in `ESP32C3 Errata <https://www.espressif.com/sites/default/files/documentation/esp32-c3_errata_en.pdf>`. For compatibility, you can enable :ref:`CONFIG_ADC_ONESHOT_FORCE_USE_ADC2_ON_C3` to force use ADC2.
+
        - ADC2 continuous (DMA) mode is no longer supported, due to hardware limitation. The results are not stable. This issue can be found in `ESP32C3 Errata <https://www.espressif.com/sites/default/files/documentation/esp32-c3_errata_en.pdf>`. For compatibility, you can enable :ref:`CONFIG_ADC_CONTINUOUS_FORCE_USE_ADC2_ON_C3_S3` to force use ADC2.
 
     .. only:: esp32s3

examples/peripherals/adc/single_read/single_read/main/single_read.c

@@ -51,7 +51,10 @@ static int adc_raw[2][10];
 static const char *TAG = "ADC SINGLE";
 
 static esp_adc_cal_characteristics_t adc1_chars;
+#if !CONFIG_IDF_TARGET_ESP32C3
+//ESP32C3 ADC2 single mode is no longer supported
 static esp_adc_cal_characteristics_t adc2_chars;
+#endif
 
 static bool adc_calibration_init(void)
 {
@@ -66,7 +69,9 @@ static bool adc_calibration_init(void)
     } else if (ret == ESP_OK) {
         cali_enable = true;
         esp_adc_cal_characterize(ADC_UNIT_1, ADC_EXAMPLE_ATTEN, ADC_WIDTH_BIT_DEFAULT, 0, &adc1_chars);
+#if !CONFIG_IDF_TARGET_ESP32C3
         esp_adc_cal_characterize(ADC_UNIT_2, ADC_EXAMPLE_ATTEN, ADC_WIDTH_BIT_DEFAULT, 0, &adc2_chars);
+#endif
     } else {
         ESP_LOGE(TAG, "Invalid arg");
     }
@@ -76,15 +81,16 @@ static bool adc_calibration_init(void)
 
 void app_main(void)
 {
-    esp_err_t ret = ESP_OK;
     uint32_t voltage = 0;
     bool cali_enable = adc_calibration_init();
 
     //ADC1 config
     ESP_ERROR_CHECK(adc1_config_width(ADC_WIDTH_BIT_DEFAULT));
     ESP_ERROR_CHECK(adc1_config_channel_atten(ADC1_EXAMPLE_CHAN0, ADC_EXAMPLE_ATTEN));
+#if !CONFIG_IDF_TARGET_ESP32C3
     //ADC2 config
     ESP_ERROR_CHECK(adc2_config_channel_atten(ADC2_EXAMPLE_CHAN0, ADC_EXAMPLE_ATTEN));
+#endif
 
     while (1) {
         adc_raw[0][0] = adc1_get_raw(ADC1_EXAMPLE_CHAN0);
@@ -95,6 +101,8 @@ void app_main(void)
         }
         vTaskDelay(pdMS_TO_TICKS(1000));
 
+#if !CONFIG_IDF_TARGET_ESP32C3
+        esp_err_t ret = ESP_OK;
         do {
             ret = adc2_get_raw(ADC2_EXAMPLE_CHAN0, ADC_WIDTH_BIT_DEFAULT, &adc_raw[1][0]);
         } while (ret == ESP_ERR_INVALID_STATE);
@@ -106,5 +114,6 @@ void app_main(void)
             ESP_LOGI(TAG_CH[1][0], "cali data: %d mV", voltage);
         }
         vTaskDelay(pdMS_TO_TICKS(1000));
+#endif
     }
 }