Analog Continuous mode API (#8715)

* Adds Analog Continuous mode API

* fix when stopping/starting ADC data are not complete

* Added example

* fix size check

* update frequency in example

* set buffer to NULL if error occurs

* add docs

* set buffer to null on error

* fix example

* update docs

* fix example

* change return value to bool type

* updated adc modes description in docs

* Add empty line at the end of sketch

cores/esp32/esp32-hal-adc.h

@@ -77,6 +77,56 @@ void analogSetWidth(uint8_t bits);
 
 #endif
 
+/*
+ * Analog Continuous mode
+ * */
+
+typedef struct {
+    uint8_t pin;           /*!<ADC pin */
+    uint8_t channel;       /*!<ADC channel */
+    int avg_read_raw;      /*!<ADC average raw data */
+    int avg_read_mvolts;   /*!<ADC average voltage in mV */
+} adc_continuos_data_t;
+
+/*
+ * Setup ADC continuous peripheral
+ * */
+bool analogContinuous(uint8_t pins[], size_t pins_count, uint32_t conversions_per_pin, uint32_t sampling_freq_hz, void (*userFunc)(void));
+
+/*
+ * Read ADC continuous conversion data
+ * */
+bool analogContinuousRead(adc_continuos_data_t ** buffer, uint32_t timeout_ms);
+
+/*
+ * Start ADC continuous conversions
+ * */
+bool analogContinuousStart();
+
+/*
+ * Stop ADC continuous conversions
+ * */
+bool analogContinuousStop();
+
+/*
+ * Deinitialize ADC continuous peripheral
+ * */
+bool analogContinuousDeinit();
+
+/*
+ * Sets the attenuation for continuous mode reading
+ * Default is 11db
+ * */
+void analogContinuousSetAtten(adc_attenuation_t attenuation);
+
+/*
+ * Sets the read resolution for continuous mode
+ * Default is 12bit (0 - 4095)
+ * Range is 9 - 12
+ * */
+void analogContinuousSetWidth(uint8_t bits);
+
+
 #ifdef __cplusplus
 }
 #endif

docs/source/api/adc.rst

@@ -11,13 +11,17 @@ to a digital form so that it can be read and processed by a microcontroller.
 ADCs are very useful in control and monitoring applications since most sensors 
 (e.g., temperature, pressure, force) produce analogue output voltages.
 
-.. note:: Each SoC or module has a different number of ADC's with a different number of channels and pins availible. Refer to datasheet of each board for more info.
+.. note:: Each SoC or module has a different number of ADC's with a different number of channels and pins available. Refer to datasheet of each board for more info.
 
 Arduino-ESP32 ADC API
 ---------------------
 
-ADC common API
-**************
+ADC OneShot mode
+****************
+
+
+The ADC OneShot mode API is fully compatible with Arduino's ``analogRead`` function. 
+When you call the ``analogRead`` or ``analogReadMillivolts`` function, it returns the result of a single conversion on the requested pin.
 
 analogRead
 ^^^^^^^^^^
@@ -82,7 +86,7 @@ The measurable input voltage differs for each chip, see table below for detailed
       ``ADC_ATTEN_DB_0``     100 mV ~ 950 mV
       ``ADC_ATTEN_DB_2_5``   100 mV ~ 1250 mV
       ``ADC_ATTEN_DB_6``     150 mV ~ 1750 mV
-      ``ADC_ATTEN_DB_11``    150 mV ~ 2450 mV
+      ``ADC_ATTEN_DB_11``    150 mV ~ 3100 mV
       =====================  ===========================================
 
    .. tab:: ESP32-S2
@@ -136,12 +140,11 @@ This function is used to set the attenuation for a specific pin/ADC channel. For
 * ``pin`` selects specific pin for attenuation settings.
 * ``attenuation`` sets the attenuation.
 
-ADC API specific for ESP32 chip
-*******************************
-
 analogSetWidth
 ^^^^^^^^^^^^^^
 
+.. note:: This function is only available for ESP32 chip.
+
 This function is used to set the hardware sample bits and read resolution.
 Default is 12bit (0 - 4095).
 Range is 9 - 12.
@@ -150,12 +153,129 @@ Range is 9 - 12.
 
     void analogSetWidth(uint8_t bits);
 
+ADC Continuous mode
+*******************
+
+ADC Continuous mode is an API designed for performing analog conversions on multiple pins in the background, 
+with the feature of receiving a callback upon completion of these conversions to access the results.
+
+This API allows you to specify the desired number of conversions per pin within a single cycle, along with its corresponding sampling rate. 
+The outcome of the ``analogContinuousRead`` function is an array of ``adc_continuous_data_t`` structures. 
+These structures hold both the raw average value and the average value in millivolts for each pin.
+
+analogContinuous
+^^^^^^^^^^^^^^^^
+
+This function is used to configure ADC continuous peripheral on selected pins.
+
+.. code-block:: arduino
+
+    bool analogContinuous(uint8_t pins[], size_t pins_count, uint32_t conversions_per_pin, uint32_t sampling_freq_hz, void (*userFunc)(void));
+
+* ``pins[]`` array of pins to be set up
+* ``pins_count`` count of pins in array
+* ``conversions_per_pin`` sets how many conversions per pin will run each ADC cycle
+* ``sampling_freq_hz`` sets sampling frequency of ADC in Hz
+* ``userFunc`` sets callback function to be called after adc conversion is done (can be set to ``NULL``)
+  
+This function will return ``true`` if configuration is successful.
+If ``false`` is returned, error occurs and ADC continuous was not configured.
+
+analogContinuousRead
+^^^^^^^^^^^^^^^^^^^^
+
+This function is used to read ADC continuous data to the result buffer. The result buffer is an array of ``adc_continuos_data_t``.
+
+.. code-block:: arduino
+
+    typedef struct {
+        uint8_t pin;           /*!<ADC pin */
+        uint8_t channel;       /*!<ADC channel */
+        int avg_read_raw;      /*!<ADC average raw data */
+        int avg_read_mvolts;   /*!<ADC average voltage in mV */
+    } adc_continuos_data_t;
+
+.. code-block:: arduino
+
+    bool analogContinuousRead(adc_continuos_data_t ** buffer, uint32_t timeout_ms);
+
+* ``buffer`` conversion result buffer to read from ADC in adc_continuos_data_t format. 
+* ``timeout_ms`` time to wait for data in milliseconds.
+  
+This function will return ``true`` if reading is successful and ``buffer`` is filled with data.
+If ``false`` is returned, reading has failed and ``buffer`` is set to NULL.
+
+analogContinuousStart
+^^^^^^^^^^^^^^^^^^^^^
+
+This function is used to start ADC continuous conversions.
+
+.. code-block:: arduino
+
+    bool analogContinuousStart();
+  
+This function will return ``true`` if ADC continuous is succesfully started.
+If ``false`` is returned, starting ADC continuous has failed.
+
+analogContinuousStop
+^^^^^^^^^^^^^^^^^^^^
+
+This function is used to stop ADC continuous conversions.
+
+.. code-block:: arduino
+
+    bool analogContinuousStop();
+  
+This function will return ``true`` if ADC continuous is succesfully stopped.
+If ``false`` is returned, stopping ADC continuous has failed.
+
+analogContinuousDeinit
+^^^^^^^^^^^^^^^^^^^^^^
+
+This function is used to deinitialize ADC continuous peripheral.
+
+.. code-block:: arduino
+
+    bool analogContinuousDeinit();
+  
+This function will return ``true`` if ADC continuous is succesfully deinitialized.
+If ``false`` is returned, deinitilization of ADC continuous has failed.
+
+analogContinuousSetAtten
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+This function is used to set the attenuation for ADC continuous peripheral. For more informations refer to `analogSetAttenuation`_.
+
+.. code-block:: arduino
+
+    void analogContinuousSetAtten(adc_attenuation_t attenuation);
+
+* ``attenuation`` sets the attenuation (default is 11db).
+
+analogContinuousSetWidth
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+This function is used to set the hardware resolution bits.
+Default value for all chips is 12bit (0 - 4095).
+
+.. note:: This function will take effect only for ESP32 chip, as it allows to set resolution in range 9-12 bits.
+
+.. code-block:: arduino
+
+    void analogContinuousSetWidth(uint8_t bits);
+
+* ``bits`` sets resolution bits.
+
+
 Example Applications
 ********************
 
-Here is an example of how to use the ADC.
+Here is an example of how to use the ADC in OneShot mode or you can run Arduino example 01.Basics -> AnalogReadSerial.
 
 .. literalinclude:: ../../../libraries/ESP32/examples/AnalogRead/AnalogRead.ino
     :language: arduino
 
-Or you can run Arduino example 01.Basics -> AnalogReadSerial.
+Here is an example of how to use the ADC in Continuous mode.
+
+.. literalinclude:: ../../../libraries/ESP32/examples/AnalogReadContinuous/AnalogReadContinuous.ino
+    :language: arduino

libraries/ESP32/examples/AnalogReadContinuous/AnalogReadContinuous.ino

+// Define how many conversion per pin will happen and reading the data will be and average of all conversions
+#define CONVERSIONS_PER_PIN 5
+
+// Declare array of ADC pins that will be used for ADC Continuous mode - ONLY ADC1 pins are supported
+// Number of selected pins can be from 1 to ALL ADC1 pins.
+#ifdef CONFIG_IDF_TARGET_ESP32
+uint8_t adc_pins[] = {36, 39, 34, 35}; //some of ADC1 pins for ESP32
+#else
+uint8_t adc_pins[] = {1, 2, 3, 4}; //ADC1 common pins for ESP32S2/S3 + ESP32C3/C6 + ESP32H2
+#endif
+
+// Calculate how many pins are declared in the array - needed as input for the setup function of ADC Continuous
+uint8_t adc_pins_count = sizeof(adc_pins) / sizeof(uint8_t);
+
+// Flag which will be set in ISR when conversion is done
+volatile bool adc_coversion_done = false;
+
+// Result structure for ADC Continuous reading
+adc_continuos_data_t * result = NULL;
+
+// ISR Function that will be triggered when ADC conversion is done
+void ARDUINO_ISR_ATTR adcComplete() {
+  adc_coversion_done = true;
+}
+
+void setup() {
+    // Initialize serial communication at 115200 bits per second:
+    Serial.begin(115200);
+
+    // Optional for ESP32: Set the resolution to 9-12 bits (default is 12 bits)
+    analogContinuousSetWidth(12);
+
+    // Optional: Set different attenaution (default is ADC_11db)
+    analogContinuousSetAtten(ADC_11db);
+
+    // Setup ADC Continuous with following input:
+    // array of pins, count of the pins, how many conversions per pin in one cycle will happen, sampling frequency, callback function
+    analogContinuous(adc_pins, adc_pins_count, CONVERSIONS_PER_PIN, 20000, &adcComplete);
+
+    // Start ADC Continuous conversions
+    analogContinuousStart();
+}
+
+void loop() {
+    // Check if conversion is done and try to read data
+    if (adc_coversion_done == true) {
+        // Set ISR flag back to false
+        adc_coversion_done = false;
+        // Read data from ADC
+        if (analogContinuousRead(&result, 0)) {
+
+            // Optional: Stop ADC Continuous conversions to have more time to process (print) the data
+            analogContinuousStop();
+
+            for (int i = 0; i < adc_pins_count; i++) {
+            Serial.printf("\nADC PIN %d data:", result[i].pin);
+            Serial.printf("\n   Avg raw value = %d", result[i].avg_read_raw);
+            Serial.printf("\n   Avg milivolts value = %d", result[i].avg_read_mvolts);
+            }
+
+            // Delay for better readability of ADC data
+            delay(1000);
+
+            // Optional: If ADC was stopped, start ADC conversions and wait for callback function to set adc_coversion_done flag to true
+            analogContinuousStart();
+        }
+        else {
+            Serial.println("Error occured during reading data. Set Core Debug Level to error or lower for more informations.");
+        }
+    }
+}