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libraries/Adafruit_Zero_PDM_Library/Adafruit_ZeroPDMSPI.h

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+/*!
+ * @file Adafruit_ZeroPDMSPI.h
+ */
+#ifndef ADAFRUIT_ZEROPDMSPI_H
+#define ADAFRUIT_ZEROPDMSPI_H
+
+/// @cond DISABLE
+#if defined(__SAMD51__)
+/// @endcond DISABLE
+
+#include <Arduino.h>
+#include <SPI.h>
+
+/*!
+ * ZeroPDM SPI driver
+ */
+class Adafruit_ZeroPDMSPI {
+ public:
+  /*!
+   * @brief Create a new instance of an PDM audio transmitter over SPI
+   * @param theSPI SPI to use
+   */
+  Adafruit_ZeroPDMSPI(SPIClass* theSPI);
+
+  /*!
+   * @brief Initialize the SPI audio receiver.
+   * @param freq Frequency (in Hertz)
+   * @return Returns if connection was successful
+   */
+  bool begin(uint32_t freq);
+
+  /*!
+   * @brief Alternates 0 to 1 to let you know that data is ready to be read
+   * @param value Variable to set the reading to
+   * @param removeDC Whether or not to remove the DC offset
+   * @return Returns if the word is even or not
+   */
+  bool decimateFilterWord(uint16_t* value, bool removeDC = true);
+
+  /*!
+   * @brief Sets the mic gain
+   * @param g Mic gain
+   */
+  void setMicGain(float g = 1.0);
+
+  /*!
+   * @brief Sample rate
+   */
+  float sampleRate;
+
+ private:
+  SPIClass* _spi = NULL;
+  Sercom* _sercom = NULL;
+  IRQn_Type _irq;
+  volatile uint32_t* _dataReg;
+
+  uint16_t dcCounter = 0;         // Rolls over every DC_PERIOD samples
+  uint32_t dcSum = 0;             // Accumulates DC_PERIOD samples
+  uint16_t dcOffsetPrior = 32768; // DC offset interpolates linearly
+  uint16_t dcOffsetNext = 32768;  // between these two values
+
+  uint16_t micGain = 256; // 1:1
+};
+
+/// @cond DISABLE
+#endif // defined(__SAMD51__)
+/// @endcond DISABLE
+
+#endif