First commit.

AudioPlayer.h

@@ -0,0 +1,65 @@
+const uint8_t *sampleName;
+uint32_t sampleSize;
+
+volatile uint16_t sampleNumber = 1;
+volatile uint8_t sampleInterruptCounter = 0;
+
+void playSample(const uint8_t *name, const uint32_t size) {
+  sampleName = name;                              // Set global variables
+  sampleSize = size;                              // for interrupt handler function
+  sampleNumber = 1;                               // Start with the second sample
+  sampleInterruptCounter = 0;                     // Counter for extrapolation/oversampling
+  REG_TC4_CTRLA |= TC_CTRLA_ENABLE;               // Enable timer TC4
+  while (TC4->COUNT16.STATUS.bit.SYNCBUSY);       // Wait for synchronization
+}
+
+void DACSetup(uint32_t sampleFreq, uint8_t bits) {
+  analogWriteResolution(bits);                    // set DAC resolution 
+  uint32_t top = 47972352 / (sampleFreq * 4);     // Calculate the TOP value from sample frequency
+  REG_GCLK_GENDIV = GCLK_GENDIV_DIV(1) |          // Divide the 48MHz clock source by divisor 1: 48MHz/1=48MHz
+                    GCLK_GENDIV_ID(4);            // Select GCLK4
+  while (GCLK->STATUS.bit.SYNCBUSY);              // Wait for synchronization
+
+  REG_GCLK_GENCTRL = GCLK_GENCTRL_IDC |           // Set the duty cycle to 50/50
+                     GCLK_GENCTRL_GENEN |         // Enable GCLK4
+                     GCLK_GENCTRL_SRC_DFLL48M |   // Set the 48MHz clock source
+                     GCLK_GENCTRL_ID(4);          // Select GCLK4
+  while (GCLK->STATUS.bit.SYNCBUSY);              // Wait for synchronization
+
+  REG_GCLK_CLKCTRL = GCLK_CLKCTRL_CLKEN |         // Enable GCLK4 to TC4 and TC5
+                     GCLK_CLKCTRL_GEN_GCLK4 |     // Select GCLK4
+                     GCLK_CLKCTRL_ID_TC4_TC5;     // Feed the GCLK4 to TC4 and TC5
+  while (GCLK->STATUS.bit.SYNCBUSY);              // Wait for synchronization
+
+  REG_TC4_COUNT16_CC0 = top;                      // Set the TC4 CC0 register as the TOP value in Match Frequency Mode
+  while (TC4->COUNT16.STATUS.bit.SYNCBUSY);       // Wait for synchronization
+
+  NVIC_SetPriority(TC4_IRQn, 0);                  // Set the Nested Vector Interrupt Controller priority for TC4 to 0 (highest)
+  NVIC_EnableIRQ(TC4_IRQn);                       // Connect TC4 to Nested Vector Interrupt Controller
+
+  REG_TC4_INTFLAG |= TC_INTFLAG_OVF;              // Clear the interrupt flags
+  REG_TC4_INTENSET = TC_INTENCLR_OVF;             // Enable TC4 interrupts
+
+  REG_TC4_CTRLA |= TC_CTRLA_PRESCALER_DIV1 |      // Set prescaler to 1, 48MHz/1 = 48MHz
+                   TC_CTRLA_WAVEGEN_MFRQ;         // Put the timer TC4 into Match Frequency Mode
+  while (TC4->COUNT16.STATUS.bit.SYNCBUSY);       // Wait for synchronization
+}
+
+void TC4_Handler() {                              // Interrupt Service Routine for timer TC4
+  sampleInterruptCounter++;
+  if (sampleInterruptCounter == 1) {
+    analogWrite(A0, (sampleName[sampleNumber] + 2 * sampleName[sampleNumber-1]) / 3);
+  } else if (sampleInterruptCounter == 2) {
+    analogWrite(A0, (sampleName[sampleNumber] + sampleName[sampleNumber-1]) / 2);
+  } else if (sampleInterruptCounter == 3) {
+    analogWrite(A0, (2 * sampleName[sampleNumber] + sampleName[sampleNumber-1]) / 3);
+  } else if (sampleInterruptCounter >= 4) {
+    analogWrite(A0, sampleName[sampleNumber++]);
+    sampleInterruptCounter = 0;
+  }
+  REG_TC4_INTFLAG = TC_INTFLAG_OVF;               // Clear the OVF interrupt flag
+  if (sampleNumber >= sampleSize) {               // When at the end of the sample array,
+    REG_TC4_CTRLA &= ~TC_CTRLA_ENABLE;            // disable timer TC4
+    while (TC4->COUNT16.STATUS.bit.SYNCBUSY);     // Wait for synchronization
+  }
+}