feature(adc): add adc example

components/esp8266/include/driver/adc.h

@@ -21,13 +21,79 @@
 extern "C" {
 #endif
 
+/**
+ * @brief ADC working mode enumeration
+ */
+typedef enum {
+    ADC_READ_TOUT_MODE,
+    ADC_READ_VDD_MODE
+} adc_mode_t;
 
 /**
-  * @brief Measure the input voltage of TOUT pin 6, unit : 1/1023 V.
+ * @brief ADC initialization parameter structure type definition
+ */
+typedef struct {
+    adc_mode_t mode;
+    uint8_t clk_div;  // ADC sample collection clock=80M/clk_div, range[8, 32]
+} adc_config_t;
+
+/**
+  * @brief Single measurement of TOUT(ADC) pin, unit : 1/1023 V or VDD pin, uint: 1 mV
   *
-  * @return Input voltage of TOUT pin 6, unit : 1/1023 V
+  * @note When measuring VDD pin voltage, the TOUT(ADC) pin must be left floating.
+  * 
+  * @param data Pointer to accept adc value.
+  *
+  * @return
+  *     - ESP_OK Success
+  *     - ESP_ERR_INVALID_ARG Parameter error
+  *     - ESP_FAIL adc has not been initialized yet
   */
-uint16_t adc_read();
+esp_err_t adc_read(uint16_t *data);
+
+/**
+  * @brief Measure the input voltage of TOUT(ADC) pin, unit : 1/1023 V.
+  *
+  * @note Wi-Fi and interrupts need to be turned off.
+  * 
+  * @param data Pointer to accept adc value. Input voltage of TOUT(ADC) pin, unit : 1/1023 V
+  * @param len Receiving length of ADC value, range [1, 65535]
+  *
+  * @return
+  *     - ESP_OK Success
+  *     - ESP_ERR_INVALID_ARG Parameter error
+  *     - ESP_FAIL adc has not been initialized yet
+  */
+esp_err_t adc_read_fast(uint16_t *data, uint16_t len);
+
+/**
+  * @brief Deinit the adc
+  *
+  * @return
+  *     - ESP_OK Success
+  *     - ESP_FAIL adc has not been initialized yet
+  */
+esp_err_t adc_deinit();
+
+/**
+  * @brief Initialize the adc
+  *
+  * @note First modify menuconfig->Component config->PHY->vdd33_const value, vdd33_const provides ADC mode settings,
+  *       i.e. selecting system voltage or external voltage measurements.
+  *       When measuring system voltage, it must be set to 255.
+  *       To read the external voltage on TOUT(ADC) pin, vdd33_const need less than 255
+  *       When the ADC reference voltage is set to the actual VDD33 power supply voltage, the value range of vdd33_const is [18,36], the unit is 0.1V.
+  *       When the ADC reference voltage is set to the default value of 3.3V as the supply voltage, the range of vdd33_const is [0, 18] or (36, 255).
+  *
+  * @param config Pointer to deliver initialize configuration parameter
+  *
+  * @return
+  *     - ESP_OK Success
+  *     - ESP_ERR_NO_MEM malloc fail
+  *     - ESP_ERR_INVALID_ARG Parameter error
+  *     - ESP_FAIL adc has been initialized
+  */
+esp_err_t adc_init(adc_config_t *config);
 
 #ifdef __cplusplus
 }