esp32/adc: Use new ADC calibration API in all cases.

Replaces the deprecated ESP32 calibration API with the "line" method
instead.

This work was funded through GitHub Sponsors.
Signed-off-by: Angus Gratton <angus@redyak.com.au>

ports/esp32/adc.c

@@ -63,22 +63,6 @@ void madcblock_bits_helper(machine_adc_block_obj_t *self, mp_int_t bits) {
     if (self->unit_id == ADC_UNIT_1) {
         adc1_config_width(self->width);
     }
-    for (adc_atten_t atten = ADC_ATTEN_DB_0; atten < ADC_ATTEN_MAX; atten++) {
-        #if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 2, 1)
-        if (self->handle[atten] != NULL) {
-            adc_cali_curve_fitting_config_t cali_config = {
-                .unit_id = self->unit_id,
-                .atten = atten,
-                .bitwidth = self->width,
-            };
-            check_esp_err(adc_cali_create_scheme_curve_fitting(&cali_config, self->handle[atten]));
-        }
-        #else
-        if (self->characteristics[atten] != NULL) {
-            esp_adc_cal_characterize(self->unit_id, atten, self->width, DEFAULT_VREF, self->characteristics[atten]);
-        }
-        #endif
-    }
 }
 
 mp_int_t madcblock_read_helper(machine_adc_block_obj_t *self, adc_channel_t channel_id) {
@@ -93,30 +77,34 @@ mp_int_t madcblock_read_helper(machine_adc_block_obj_t *self, adc_channel_t chan
     return raw;
 }
 
-mp_int_t madcblock_read_uv_helper(machine_adc_block_obj_t *self, adc_channel_t channel_id, adc_atten_t atten) {
-    int raw = madcblock_read_helper(self, channel_id);
-    #if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 2, 1)
-    adc_cali_handle_t *adc_handle = self->handle[atten];
-    if (adc_handle == NULL) {
-        adc_cali_curve_fitting_config_t cali_config = {
-            .unit_id = self->unit_id,
-            .atten = atten,
-            .bitwidth = self->width,
-        };
-        adc_handle = malloc(sizeof(adc_cali_handle_t));
-        check_esp_err(adc_cali_create_scheme_curve_fitting(&cali_config, adc_handle));
-        self->handle[atten] = adc_handle;
+static esp_err_t ensure_adc_calibration(machine_adc_block_obj_t *self, adc_atten_t atten) {
+    if (self->handle[atten] != NULL) {
+        return ESP_OK;
     }
-    int uv;
-    check_esp_err(adc_cali_raw_to_voltage(*adc_handle, raw, &uv));
+
+    #if ADC_CALI_SCHEME_CURVE_FITTING_SUPPORTED
+    adc_cali_curve_fitting_config_t cali_config = {
+        .unit_id = self->unit_id,
+        .atten = atten,
+        .bitwidth = self->width,
+    };
+    return adc_cali_create_scheme_curve_fitting(&cali_config, &self->handle[atten]);
     #else
-    esp_adc_cal_characteristics_t *adc_chars = self->characteristics[atten];
-    if (adc_chars == NULL) {
-        adc_chars = malloc(sizeof(esp_adc_cal_characteristics_t));
-        esp_adc_cal_characterize(self->unit_id, atten, self->width, DEFAULT_VREF, adc_chars);
-        self->characteristics[atten] = adc_chars;
-    }
-    mp_int_t uv = esp_adc_cal_raw_to_voltage(raw, adc_chars);
+    adc_cali_line_fitting_config_t cali_config = {
+        .unit_id = self->unit_id,
+        .atten = atten,
+        .bitwidth = self->width,
+    };
+    return adc_cali_create_scheme_line_fitting(&cali_config, &self->handle[atten]);
     #endif
+}
+
+mp_int_t madcblock_read_uv_helper(machine_adc_block_obj_t *self, adc_channel_t channel_id, adc_atten_t atten) {
+    int raw = madcblock_read_helper(self, channel_id);
+    int uv;
+
+    check_esp_err(ensure_adc_calibration(self, atten));
+    check_esp_err(adc_cali_raw_to_voltage(self->handle[atten], raw, &uv));
+
     return (mp_int_t)uv * 1000;
 }

ports/esp32/adc.h

@@ -39,11 +39,7 @@ typedef struct _machine_adc_block_obj_t {
     adc_unit_t unit_id;
     mp_int_t bits;
     adc_bits_width_t width;
-    #if ESP_IDF_VERSION >= ESP_IDF_VERSION_VAL(5, 2, 1)
-    adc_cali_handle_t *handle[ADC_ATTEN_MAX];
-    #else
-    esp_adc_cal_characteristics_t *characteristics[ADC_ATTEN_MAX];
-    #endif
+    adc_cali_handle_t handle[ADC_ATTEN_MAX];
 } machine_adc_block_obj_t;
 
 typedef struct _machine_adc_obj_t {