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Changed AudioInput and AudioOutput demos to reload the next sample via an interrupt rather than polling the sample timer.

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This commit is contained in:
Dean Camera 2010-10-26 06:52:09 +00:00
parent 55538dcef3
commit 08de757811
10 changed files with 88 additions and 112 deletions
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63
Demos/Device/ClassDriver/AudioOutput/AudioOutput.c
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@ -63,8 +63,6 @@ int main(void)
for (;;)
{
ProcessNextSample();
Audio_Device_USBTask(&Speaker_Audio_Interface);
USB_USBTask();
}
@ -85,35 +83,31 @@ void SetupHardware(void)
USB_Init();
}
/** Processes the next audio sample by reading the last ADC conversion and writing it to the audio
* interface, each time the sample reload timer period elapses to give a constant sample rate.
*/
void ProcessNextSample(void)
/** ISR to handle the reloading of the PWM timer with the next sample. */
ISR(TIMER0_COMPA_vect, ISR_BLOCK)
{
/* Check if the sample reload timer period has elapsed, and that the USB bus is ready for a new sample */
if ((TIFR0 & (1 << OCF0A)) && Audio_Device_IsSampleReceived(&Speaker_Audio_Interface))
{
/* Clear the sample reload timer compare flag, ready for the next interval */
TIFR0 |= (1 << OCF0A);
uint8_t PrevEndpoint = Endpoint_GetCurrentEndpoint();
if (Audio_Device_IsSampleReceived(&Speaker_Audio_Interface))
{
/* Retrieve the signed 16-bit left and right audio samples, convert to 8-bit */
int8_t LeftSample_8Bit = (Audio_Device_ReadSample16(&Speaker_Audio_Interface) >> 8);
int8_t RightSample_8Bit = (Audio_Device_ReadSample16(&Speaker_Audio_Interface) >> 8);
int8_t LeftSample_8Bit = (Audio_Device_ReadSample16(&Speaker_Audio_Interface) >> 8);
int8_t RightSample_8Bit = (Audio_Device_ReadSample16(&Speaker_Audio_Interface) >> 8);
/* Mix the two channels together to produce a mono, 8-bit sample */
int8_t MixedSample_8Bit = (((int16_t)LeftSample_8Bit + (int16_t)RightSample_8Bit) >> 1);
int8_t MixedSample_8Bit = (((int16_t)LeftSample_8Bit + (int16_t)RightSample_8Bit) >> 1);
#if defined(AUDIO_OUT_MONO)
#if defined(AUDIO_OUT_MONO)
/* Load the sample into the PWM timer channel */
OCR3A = (MixedSample_8Bit ^ (1 << 7));
#elif defined(AUDIO_OUT_STEREO)
#elif defined(AUDIO_OUT_STEREO)
/* Load the dual 8-bit samples into the PWM timer channels */
OCR3A = (LeftSample_8Bit ^ (1 << 7));
OCR3B = (RightSample_8Bit ^ (1 << 7));
#elif defined(AUDIO_OUT_PORTC)
#elif defined(AUDIO_OUT_PORTC)
/* Load the 8-bit mixed sample into PORTC */
PORTC = MixedSample_8Bit;
#endif
#endif
uint8_t LEDMask = LEDS_NO_LEDS;
@ -129,6 +123,8 @@ void ProcessNextSample(void)
LEDs_SetAllLEDs(LEDMask);
}
Endpoint_SelectEndpoint(PrevEndpoint);
}
/** Event handler for the library USB Connection event. */
@ -137,27 +133,28 @@ void EVENT_USB_Device_Connect(void)
LEDs_SetAllLEDs(LEDMASK_USB_ENUMERATING);
/* Sample reload timer initialization */
TIMSK0 = (1 << OCIE0A);
OCR0A = (F_CPU / 8 / AUDIO_SAMPLE_FREQUENCY) - 1;
TCCR0A = (1 << WGM01); // CTC mode
TCCR0B = (1 << CS01); // Fcpu/8 speed
#if defined(AUDIO_OUT_MONO)
#if defined(AUDIO_OUT_MONO)
/* Set speaker as output */
DDRC |= (1 << 6);
#elif defined(AUDIO_OUT_STEREO)
#elif defined(AUDIO_OUT_STEREO)
/* Set speakers as outputs */
DDRC |= ((1 << 6) | (1 << 5));
#elif defined(AUDIO_OUT_PORTC)
#elif defined(AUDIO_OUT_PORTC)
/* Set PORTC as outputs */
DDRC |= 0xFF;
#endif
#endif
#if (defined(AUDIO_OUT_MONO) || defined(AUDIO_OUT_STEREO))
#if (defined(AUDIO_OUT_MONO) || defined(AUDIO_OUT_STEREO))
/* PWM speaker timer initialization */
TCCR3A = ((1 << WGM30) | (1 << COM3A1) | (1 << COM3A0)
| (1 << COM3B1) | (1 << COM3B0)); // Set on match, clear on TOP
TCCR3B = ((1 << WGM32) | (1 << CS30)); // Fast 8-Bit PWM, F_CPU speed
#endif
#endif
}
/** Event handler for the library USB Disconnection event. */
@ -168,21 +165,21 @@ void EVENT_USB_Device_Disconnect(void)
/* Stop the sample reload timer */
TCCR0B = 0;
#if (defined(AUDIO_OUT_MONO) || defined(AUDIO_OUT_STEREO))
#if (defined(AUDIO_OUT_MONO) || defined(AUDIO_OUT_STEREO))
/* Stop the PWM generation timer */
TCCR3B = 0;
#endif
#endif
#if defined(AUDIO_OUT_MONO)
#if defined(AUDIO_OUT_MONO)
/* Set speaker as input to reduce current draw */
DDRC &= ~(1 << 6);
#elif defined(AUDIO_OUT_STEREO)
DDRC &= ~(1 << 6);
#elif defined(AUDIO_OUT_STEREO)
/* Set speakers as inputs to reduce current draw */
DDRC &= ~((1 << 6) | (1 << 5));
#elif defined(AUDIO_OUT_PORTC)
DDRC &= ~((1 << 6) | (1 << 5));
#elif defined(AUDIO_OUT_PORTC)
/* Set PORTC low */
PORTC = 0x00;
#endif
PORTC = 0x00;
#endif
}
/** Event handler for the library USB Configuration Changed event. */