From 08de757811bb2a17d21a35ca08205b4ed64613ff Mon Sep 17 00:00:00 2001 From: Dean Camera Date: Tue, 26 Oct 2010 06:52:09 +0000 Subject: Changed AudioInput and AudioOutput demos to reload the next sample via an interrupt rather than polling the sample timer. --- Demos/Device/ClassDriver/AudioOutput/AudioOutput.c | 63 +++++++++++----------- Demos/Device/ClassDriver/AudioOutput/AudioOutput.h | 1 - 2 files changed, 30 insertions(+), 34 deletions(-) (limited to 'Demos/Device/ClassDriver/AudioOutput') diff --git a/Demos/Device/ClassDriver/AudioOutput/AudioOutput.c b/Demos/Device/ClassDriver/AudioOutput/AudioOutput.c index 33b52a184..463837934 100644 --- a/Demos/Device/ClassDriver/AudioOutput/AudioOutput.c +++ b/Demos/Device/ClassDriver/AudioOutput/AudioOutput.c @@ -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. */ diff --git a/Demos/Device/ClassDriver/AudioOutput/AudioOutput.h b/Demos/Device/ClassDriver/AudioOutput/AudioOutput.h index c03a82050..825af6853 100644 --- a/Demos/Device/ClassDriver/AudioOutput/AudioOutput.h +++ b/Demos/Device/ClassDriver/AudioOutput/AudioOutput.h @@ -64,7 +64,6 @@ /* Function Prototypes: */ void SetupHardware(void); - void ProcessNextSample(void); void EVENT_USB_Device_Connect(void); void EVENT_USB_Device_Disconnect(void); -- cgit v1.2.3