diff options
Diffstat (limited to 'Demos/Device/LowLevel')
| -rw-r--r-- | Demos/Device/LowLevel/AudioOutput/AudioOutput.c | 35 |
1 files changed, 14 insertions, 21 deletions
diff --git a/Demos/Device/LowLevel/AudioOutput/AudioOutput.c b/Demos/Device/LowLevel/AudioOutput/AudioOutput.c index dd880b437..28e57c48c 100644 --- a/Demos/Device/LowLevel/AudioOutput/AudioOutput.c +++ b/Demos/Device/LowLevel/AudioOutput/AudioOutput.c @@ -195,9 +195,12 @@ void USB_Audio_Task(void) /* Clear the sample reload timer */
TIFR0 |= (1 << OCF0A);
- /* Retrieve the signed 16-bit left and right audio samples */
- int16_t LeftSample_16Bit = (int16_t)Endpoint_Read_Word_LE();
- int16_t RightSample_16Bit = (int16_t)Endpoint_Read_Word_LE();
+ /* Retrieve the signed 16-bit left and right audio samples, convert to 8-bit */
+ int8_t LeftSample_8Bit = ((int16_t)Endpoint_Read_Word_LE() >> 8);
+ int8_t RightSample_8Bit = ((int16_t)Endpoint_Read_Word_LE() >> 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);
/* Check to see if the bank is now empty */
if (!(Endpoint_IsReadWriteAllowed()))
@@ -206,23 +209,13 @@ void USB_Audio_Task(void) Endpoint_ClearOUT();
}
- /* Massage signed 16-bit left and right audio samples into signed 8-bit */
- int8_t LeftSample_8Bit = (LeftSample_16Bit >> 8);
- int8_t RightSample_8Bit = (RightSample_16Bit >> 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);
-
- /* Get absolute value of mixed sample value */
- uint8_t MixedSample_8Bit_Abs = abs(MixedSample_8Bit);
-
#if defined(AUDIO_OUT_MONO)
/* Load the sample into the PWM timer channel */
- OCR3A = ((uint8_t)MixedSample_8Bit ^ (1 << 7));
+ OCR3A = (MixedSample_8Bit ^ (1 << 7));
#elif defined(AUDIO_OUT_STEREO)
/* Load the dual 8-bit samples into the PWM timer channels */
- OCR3A = ((uint8_t)LeftSample_8Bit ^ (1 << 7));
- OCR3B = ((uint8_t)RightSample_8Bit ^ (1 << 7));
+ OCR3A = (LeftSample_8Bit ^ (1 << 7));
+ OCR3B = (RightSample_8Bit ^ (1 << 7));
#elif defined(AUDIO_OUT_PORTC)
/* Load the 8-bit mixed sample into PORTC */
PORTC = MixedSample_8Bit;
@@ -231,15 +224,15 @@ void USB_Audio_Task(void) uint8_t LEDMask = LEDS_NO_LEDS;
/* Turn on LEDs as the sample amplitude increases */
- if (MixedSample_8Bit_Abs > 16)
+ if (MixedSample_8Bit > 16)
LEDMask = (LEDS_LED1 | LEDS_LED2 | LEDS_LED3 | LEDS_LED4);
- else if (MixedSample_8Bit_Abs > 8)
+ else if (MixedSample_8Bit > 8)
LEDMask = (LEDS_LED1 | LEDS_LED2 | LEDS_LED3);
- else if (MixedSample_8Bit_Abs > 4)
+ else if (MixedSample_8Bit > 4)
LEDMask = (LEDS_LED1 | LEDS_LED2);
- else if (MixedSample_8Bit_Abs > 2)
+ else if (MixedSample_8Bit > 2)
LEDMask = (LEDS_LED1);
-
+
LEDs_SetAllLEDs(LEDMask);
}
}
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