initial commit

libraries/Adafruit_Zero_PDM_Library/examples/spipdm_analogout/spipdm_analogout.ino

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+#include <SPI.h>
+#include <Adafruit_ZeroPDMSPI.h>
+
+#define PDM_SPI            SPI2    // PDM mic SPI peripheral
+#define PDM_SERCOM_HANDLER SERCOM3_0_Handler
+
+Adafruit_ZeroPDMSPI pdmspi(&PDM_SPI);
+
+// INTERRUPT HANDLERS ------------------------------------------------------
+volatile int16_t pdmLastReading = 0;
+void PDM_SERCOM_HANDLER(void) {
+  digitalWrite(13, HIGH);
+  uint16_t v = 0;
+  if (pdmspi.decimateFilterWord(&v)) {
+    pdmLastReading = (int32_t)v - 32768;
+  }
+  digitalWrite(13, LOW);
+}
+
+void setup() {
+  while (!Serial) delay(10);
+  Serial.begin(115200);
+  pinMode(13, OUTPUT);
+  delay(100);
+  Serial.println("PDM Mic test");
+  Serial.println("-------------------");
+  
+  pdmspi.begin(16000);
+  Serial.print("Final PDM frequency: "); Serial.println(pdmspi.sampleRate);
+
+  // Set up analog output ------------------------------------------
+  analogWriteResolution(12);
+}
+
+void loop() {
+  analogWrite(A0, 2048 + pdmLastReading / 16);
+  //Serial.println(voiceLastReading);
+}