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@ -63,8 +63,6 @@ int main(void)
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for (;;)
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for (;;)
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{
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{
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ProcessNextSample();
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Audio_Device_USBTask(&Speaker_Audio_Interface);
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Audio_Device_USBTask(&Speaker_Audio_Interface);
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USB_USBTask();
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USB_USBTask();
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}
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}
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@ -85,17 +83,13 @@ void SetupHardware(void)
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USB_Init();
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USB_Init();
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}
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}
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/** Processes the next audio sample by reading the last ADC conversion and writing it to the audio
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/** ISR to handle the reloading of the PWM timer with the next sample. */
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* interface, each time the sample reload timer period elapses to give a constant sample rate.
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ISR(TIMER0_COMPA_vect, ISR_BLOCK)
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*/
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void ProcessNextSample(void)
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{
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{
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/* Check if the sample reload timer period has elapsed, and that the USB bus is ready for a new sample */
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uint8_t PrevEndpoint = Endpoint_GetCurrentEndpoint();
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if ((TIFR0 & (1 << OCF0A)) && Audio_Device_IsSampleReceived(&Speaker_Audio_Interface))
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{
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/* Clear the sample reload timer compare flag, ready for the next interval */
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TIFR0 |= (1 << OCF0A);
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if (Audio_Device_IsSampleReceived(&Speaker_Audio_Interface))
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{
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/* Retrieve the signed 16-bit left and right audio samples, convert to 8-bit */
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/* Retrieve the signed 16-bit left and right audio samples, convert to 8-bit */
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int8_t LeftSample_8Bit = (Audio_Device_ReadSample16(&Speaker_Audio_Interface) >> 8);
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int8_t LeftSample_8Bit = (Audio_Device_ReadSample16(&Speaker_Audio_Interface) >> 8);
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int8_t RightSample_8Bit = (Audio_Device_ReadSample16(&Speaker_Audio_Interface) >> 8);
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int8_t RightSample_8Bit = (Audio_Device_ReadSample16(&Speaker_Audio_Interface) >> 8);
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@ -103,17 +97,17 @@ void ProcessNextSample(void)
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/* Mix the two channels together to produce a mono, 8-bit sample */
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/* Mix the two channels together to produce a mono, 8-bit sample */
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int8_t MixedSample_8Bit = (((int16_t)LeftSample_8Bit + (int16_t)RightSample_8Bit) >> 1);
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int8_t MixedSample_8Bit = (((int16_t)LeftSample_8Bit + (int16_t)RightSample_8Bit) >> 1);
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#if defined(AUDIO_OUT_MONO)
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#if defined(AUDIO_OUT_MONO)
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/* Load the sample into the PWM timer channel */
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/* Load the sample into the PWM timer channel */
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OCR3A = (MixedSample_8Bit ^ (1 << 7));
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OCR3A = (MixedSample_8Bit ^ (1 << 7));
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#elif defined(AUDIO_OUT_STEREO)
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#elif defined(AUDIO_OUT_STEREO)
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/* Load the dual 8-bit samples into the PWM timer channels */
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/* Load the dual 8-bit samples into the PWM timer channels */
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OCR3A = (LeftSample_8Bit ^ (1 << 7));
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OCR3A = (LeftSample_8Bit ^ (1 << 7));
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OCR3B = (RightSample_8Bit ^ (1 << 7));
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OCR3B = (RightSample_8Bit ^ (1 << 7));
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#elif defined(AUDIO_OUT_PORTC)
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#elif defined(AUDIO_OUT_PORTC)
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/* Load the 8-bit mixed sample into PORTC */
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/* Load the 8-bit mixed sample into PORTC */
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PORTC = MixedSample_8Bit;
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PORTC = MixedSample_8Bit;
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#endif
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#endif
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uint8_t LEDMask = LEDS_NO_LEDS;
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uint8_t LEDMask = LEDS_NO_LEDS;
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@ -129,6 +123,8 @@ void ProcessNextSample(void)
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LEDs_SetAllLEDs(LEDMask);
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LEDs_SetAllLEDs(LEDMask);
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}
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}
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Endpoint_SelectEndpoint(PrevEndpoint);
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}
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}
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/** Event handler for the library USB Connection event. */
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/** Event handler for the library USB Connection event. */
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@ -137,27 +133,28 @@ void EVENT_USB_Device_Connect(void)
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LEDs_SetAllLEDs(LEDMASK_USB_ENUMERATING);
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LEDs_SetAllLEDs(LEDMASK_USB_ENUMERATING);
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/* Sample reload timer initialization */
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/* Sample reload timer initialization */
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TIMSK0 = (1 << OCIE0A);
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OCR0A = (F_CPU / 8 / AUDIO_SAMPLE_FREQUENCY) - 1;
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OCR0A = (F_CPU / 8 / AUDIO_SAMPLE_FREQUENCY) - 1;
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TCCR0A = (1 << WGM01); // CTC mode
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TCCR0A = (1 << WGM01); // CTC mode
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TCCR0B = (1 << CS01); // Fcpu/8 speed
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TCCR0B = (1 << CS01); // Fcpu/8 speed
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#if defined(AUDIO_OUT_MONO)
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#if defined(AUDIO_OUT_MONO)
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/* Set speaker as output */
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/* Set speaker as output */
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DDRC |= (1 << 6);
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DDRC |= (1 << 6);
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#elif defined(AUDIO_OUT_STEREO)
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#elif defined(AUDIO_OUT_STEREO)
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/* Set speakers as outputs */
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/* Set speakers as outputs */
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DDRC |= ((1 << 6) | (1 << 5));
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DDRC |= ((1 << 6) | (1 << 5));
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#elif defined(AUDIO_OUT_PORTC)
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#elif defined(AUDIO_OUT_PORTC)
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/* Set PORTC as outputs */
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/* Set PORTC as outputs */
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DDRC |= 0xFF;
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DDRC |= 0xFF;
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#endif
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#endif
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#if (defined(AUDIO_OUT_MONO) || defined(AUDIO_OUT_STEREO))
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#if (defined(AUDIO_OUT_MONO) || defined(AUDIO_OUT_STEREO))
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/* PWM speaker timer initialization */
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/* PWM speaker timer initialization */
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TCCR3A = ((1 << WGM30) | (1 << COM3A1) | (1 << COM3A0)
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TCCR3A = ((1 << WGM30) | (1 << COM3A1) | (1 << COM3A0)
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| (1 << COM3B1) | (1 << COM3B0)); // Set on match, clear on TOP
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| (1 << COM3B1) | (1 << COM3B0)); // Set on match, clear on TOP
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TCCR3B = ((1 << WGM32) | (1 << CS30)); // Fast 8-Bit PWM, F_CPU speed
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TCCR3B = ((1 << WGM32) | (1 << CS30)); // Fast 8-Bit PWM, F_CPU speed
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#endif
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#endif
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}
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}
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/** Event handler for the library USB Disconnection event. */
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/** Event handler for the library USB Disconnection event. */
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@ -168,21 +165,21 @@ void EVENT_USB_Device_Disconnect(void)
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/* Stop the sample reload timer */
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/* Stop the sample reload timer */
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TCCR0B = 0;
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TCCR0B = 0;
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#if (defined(AUDIO_OUT_MONO) || defined(AUDIO_OUT_STEREO))
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#if (defined(AUDIO_OUT_MONO) || defined(AUDIO_OUT_STEREO))
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/* Stop the PWM generation timer */
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/* Stop the PWM generation timer */
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TCCR3B = 0;
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TCCR3B = 0;
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#endif
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#endif
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#if defined(AUDIO_OUT_MONO)
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#if defined(AUDIO_OUT_MONO)
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/* Set speaker as input to reduce current draw */
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/* Set speaker as input to reduce current draw */
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DDRC &= ~(1 << 6);
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DDRC &= ~(1 << 6);
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#elif defined(AUDIO_OUT_STEREO)
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#elif defined(AUDIO_OUT_STEREO)
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/* Set speakers as inputs to reduce current draw */
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/* Set speakers as inputs to reduce current draw */
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DDRC &= ~((1 << 6) | (1 << 5));
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DDRC &= ~((1 << 6) | (1 << 5));
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#elif defined(AUDIO_OUT_PORTC)
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#elif defined(AUDIO_OUT_PORTC)
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/* Set PORTC low */
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/* Set PORTC low */
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PORTC = 0x00;
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PORTC = 0x00;
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#endif
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#endif
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}
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}
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/** Event handler for the library USB Configuration Changed event. */
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/** Event handler for the library USB Configuration Changed event. */
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