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libraries/FreeRTOS/examples/GoldilocksAnalogueTestSuite/GA_Header.h

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+#ifndef GA_HEADER_h // include guard
+#define GA_HEADER_h
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <avr/io.h>
+
+/*--------------------------------------------------*/
+/*------------Often Configured Parameters-----------*/
+/*--------------------------------------------------*/
+
+#define SAMPLE_RATE   16000   // samples per second
+#define DELAY         128000  // bytes of delay
+
+/* Working buffer */
+#define CMD_BUFFER_SIZE 8192  // size of working buffer (on heap)
+
+/*--------------------------------------------------*/
+/*---------------Public Functions-------------------*/
+/*--------------------------------------------------*/
+
+void AudioCodec_ADC_init(void) __attribute__((flatten));
+void AudioCodec_ADC(uint16_t* _modvalue) __attribute__((hot, flatten));
+
+void alaw_compress1(int16_t* linval, uint8_t* logval) __attribute__ ((hot, flatten));
+void alaw_expand1(uint8_t* logval, int16_t* linval) __attribute__ ((hot, flatten));
+
+void audioCodec_dsp( uint16_t* ch_A, uint16_t* ch_B) __attribute__ ((hot, flatten));
+// prototype for the DSP function to be implemented.
+// needs to at least provide *ch_A and *ch_B
+// within Timer1 interrupt routine - time critical I/O. Keep it short and punchy!
+
+/*--------------------------------------------------*/
+
+void AudioCodec_ADC_init(void)
+{
+  // setup ADCs
+  ADMUX  = _BV(REFS1) | _BV(REFS0) | _BV(ADLAR) | _BV(MUX2) | _BV(MUX1) | _BV(MUX0); // 2.56V reference with external capacitor at AREF pin - left justify - start sampling MIC input ADC7
+  ADCSRA = _BV(ADEN) | _BV(ADSC) | _BV(ADATE) | _BV(ADPS2) | _BV(ADPS1) | _BV(ADPS0); // ADC enable, auto trigger, ck/128 = 192kHz
+  ADCSRB =  0x00;     // free running mode
+  DIDR0  = _BV(ADC7D) | _BV(ADC6D) | _BV(ADC2D) | _BV(ADC1D) | _BV(ADC0D); // turn off digital input for pin ADC6 Line and ADC7 Mic input (and ADC2, ADC1, & ADC0)
+
+  // Analogue Comparator Disable
+  // When the ACD bit is written logic one, the power to the Analogue Comparator is switched off.
+  // This bit can be set at any time to turn off the Analogue Comparator.
+  // This will reduce power consumption in Active and Idle mode.
+  // When changing the ACD bit, the Analogue Comparator Interrupt must be disabled by clearing the ACIE bit in ACSR.
+  // Otherwise an interrupt can occur when the ACD bit is changed.
+  ACSR &= ~_BV(ACIE);
+  ACSR |= _BV(ACD);
+
+}
+
+// adc sampling routine
+void AudioCodec_ADC(uint16_t* _modvalue)
+{
+  if (ADCSRA & _BV(ADIF))       // check if sample ready
+  {
+    *_modvalue = ADCW;          // fetch ADCL first to freeze sample, then ADCH. It is done by the compiler.
+    ADCSRA |= _BV(ADIF);        // reset the interrupt flag
+  }
+}
+
+/*
+  ==========================================================================
+
+   FUNCTION NAME: alaw_compress11
+
+   DESCRIPTION: ALaw encoding rule according ITU-T Rec. G.711.
+
+   PROTOTYPE: int8_t alaw_compress1( int16_t linval )
+   PARAMETERS:
+     linval:  (In)  linear samples (only 12 MSBits are taken into account)
+     logval:  (Out) compressed sample (8 bit right justified without sign extension)
+
+   RETURN VALUE: none.
+
+  ==========================================================================
+*/
+void alaw_compress1 (int16_t* linval, uint8_t* logval)
+{
+  uint16_t ix, iexp;
+
+  ix = *linval < 0    /* 0 <= ix < 2048 */
+       ? ~*linval >> 4 /* 1's complement for negative values */
+       :  *linval >> 4;
+
+  /* Do more, if exponent > 0 */
+  if (ix > 15)    /* exponent=0 for ix <= 15 */
+  {
+    iexp = 1;     /* first step: */
+    while (ix > 16 + 15)  /* find mantissa and exponent */
+    {
+      ix >>= 1;
+      iexp++;
+    }
+    ix -= 16;     /* second step: remove leading '1' */
+
+    ix += iexp << 4;    /* now compute encoded value */
+  }
+
+  if (*linval >= 0) ix |= (0x0080); /* add sign bit */
+
+  *logval = (uint8_t)(ix ^ (0x0055)); /* toggle even bits */
+}
+/* ................... End of alaw_compress1() ..................... */
+
+
+/*
+  ==========================================================================
+
+   FUNCTION NAME: alaw_expand1
+
+   DESCRIPTION: ALaw decoding rule according ITU-T Rec. G.711.
+
+   PROTOTYPE: int16_t alaw_expand1( uint8_t logval )
+
+   PARAMETERS:
+     logval:  (In)  buffer with compressed samples (8 bit right justified,
+                      without sign extension)
+     linval:  (Out) buffer with linear samples (13 bits left justified)
+
+   RETURN VALUE: none.
+  ============================================================================
+*/
+void alaw_expand1(uint8_t* logval, int16_t* linval)
+{
+  uint8_t  ix, iexp;
+  int16_t mant;
+
+  ix = (*logval ^ (0x55));  /* re-toggle toggled even bits */
+
+  ix &= 0x7F;     /* remove sign bit */
+  iexp = ix >> 4;   /* extract exponent */
+  mant = ix & 0x0f; /* now get mantissa */
+  if (iexp > 0)
+    mant = mant + 16; /* add leading '1', if exponent > 0 */
+
+  mant = (mant << 4) + (0x0008);  /* now mantissa left justified and */
+  /* 1/2 quantization step added */
+  if (iexp > 1)   /* now left shift according exponent */
+    mant = mant << (iexp - 1);
+
+  *linval = *logval > 127 /* invert, if negative sample */
+            ? mant
+            : -mant;
+}
+/* ................... End of alaw_expand1() ..................... */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // GA_HEADER_h end include guard