File content as of revision 0:bf7b9fba3924:

/*----------------------------------------------------------------------------
 * Name:    usbmain.c
 * Purpose: USB Audio Class Demo
 * Version: V1.20
 *----------------------------------------------------------------------------
 *      This software is supplied "AS IS" without any warranties, express,
 *      implied or statutory, including but not limited to the implied
 *      warranties of fitness for purpose, satisfactory quality and
 *      noninfringement. Keil extends you a royalty-free right to reproduce
 *      and distribute executable files created using this software for use
 *      on NXP Semiconductors LPC microcontroller devices only. Nothing else
 *      gives you the right to use this software.
 *
 * Copyright (c) 2009 Keil - An ARM Company. All rights reserved.
 *---------------------------------------------------------------------------*/

#include "LPC17xx.h"                        /* LPC17xx definitions */
#include "lpc_types.h"

#include "usb.h"
#include "usbcfg.h"
#include "usbhw.h"
#include "usbcore.h"
#include "usbaudio.h"

/* Example group ----------------------------------------------------------- */
/** @defgroup USBDEV_USBAudio	USBAudio
 * @ingroup USBDEV_Examples
 * @{
 */
uint8_t  Mute;                                 /* Mute State */
uint32_t Volume;                               /* Volume Level */

#if USB_DMA
uint32_t *InfoBuf = (uint32_t *)(DMA_BUF_ADR);
short *DataBuf = (short *)(DMA_BUF_ADR + 4*P_C);
#else
uint32_t InfoBuf[P_C];
short DataBuf[B_S];                         /* Data Buffer */
#endif

uint16_t  DataOut;                              /* Data Out Index */
uint16_t  DataIn;                               /* Data In Index */

uint8_t   DataRun;                              /* Data Stream Run State */
uint16_t  PotVal;                               /* Potenciometer Value */
uint32_t  VUM;                                  /* VU Meter */
uint32_t  Tick;                                 /* Time Tick */


/*
 * Get Potenciometer Value
 */

void get_potval (void) {
  uint32_t val;

  LPC_ADC->ADCR |= 0x01000000;              /* Start A/D Conversion */
  do {
    val = LPC_ADC->ADGDR;                   /* Read A/D Data Register */
  } while ((val & 0x80000000) == 0);        /* Wait for end of A/D Conversion */
  LPC_ADC->ADCR &= ~0x01000000;             /* Stop A/D Conversion */
  PotVal = ((val >> 8) & 0xF8) +            /* Extract Potenciometer Value */
           ((val >> 7) & 0x08);
}


/*
 * Timer Counter 0 Interrupt Service Routine
 *   executed each 31.25us (32kHz frequency)
 */

void TIMER0_IRQHandler(void)
{
  long  val;
  uint32_t cnt;

  if (DataRun) {                            /* Data Stream is running */
    val = DataBuf[DataOut];                 /* Get Audio Sample */
    cnt = (DataIn - DataOut) & (B_S - 1);   /* Buffer Data Count */
    if (cnt == (B_S - P_C*P_S)) {           /* Too much Data in Buffer */
      DataOut++;                            /* Skip one Sample */
    }
    if (cnt > (P_C*P_S)) {                  /* Still enough Data in Buffer */
      DataOut++;                            /* Update Data Out Index */
    }
    DataOut &= B_S - 1;                     /* Adjust Buffer Out Index */
    if (val < 0) VUM -= val;                /* Accumulate Neg Value */
    else         VUM += val;                /* Accumulate Pos Value */
    val  *= Volume;                         /* Apply Volume Level */
    val >>= 16;                             /* Adjust Value */
    val  += 0x8000;                         /* Add Bias */
    val  &= 0xFFFF;                         /* Mask Value */
  } else {
    val = 0x8000;                           /* DAC Middle Point */
  }

  if (Mute) {
    val = 0x8000;                           /* DAC Middle Point */
  }

  LPC_DAC->DACR = val & 0xFFC0;             /* Set Speaker Output */

  if ((Tick++ & 0x03FF) == 0) {             /* On every 1024th Tick */
    get_potval();                           /* Get Potenciometer Value */
    if (VolCur == 0x8000) {                 /* Check for Minimum Level */
      Volume = 0;                           /* No Sound */
    } else {
      Volume = VolCur * PotVal;             /* Chained Volume Level */
    }
    val = VUM >> 20;                        /* Scale Accumulated Value */
    VUM = 0;                                /* Clear VUM */
    if (val > 7) val = 7;                   /* Limit Value */
  }

  LPC_TIM0->IR = 1;                         /* Clear Interrupt Flag */
}



/*****************************************************************************
**   Main Function  main()
******************************************************************************/
int main (void)
{
  volatile uint32_t pclkdiv, pclk;

//  SystemInit();

  LPC_PINCON->PINSEL1 &=~((0x03<<18)|(0x03<<20));
  /* P0.25, A0.0, function 01, P0.26 AOUT, function 10 */
  LPC_PINCON->PINSEL1 |= ((0x01<<18)|(0x02<<20));

  /* Enable CLOCK into ADC controller */
  LPC_SC->PCONP |= (1 << 12);

  LPC_ADC->ADCR = 0x00200E04;		/* ADC: 10-bit AIN2 @ 4MHz */
  LPC_DAC->DACR = 0x00008000;		/* DAC Output set to Middle Point */

  /* By default, the PCLKSELx value is zero, thus, the PCLK for
  all the peripherals is 1/4 of the SystemFrequency. */
  /* Bit 2~3 is for TIMER0 */
  pclkdiv = (LPC_SC->PCLKSEL0 >> 2) & 0x03;
  switch ( pclkdiv )
  {
	case 0x00:
	default:
	  pclk = SystemCoreClock/4;
	break;
	case 0x01:
	  pclk = SystemCoreClock;
	break;
	case 0x02:
	  pclk = SystemCoreClock/2;
	break;
	case 0x03:
	  pclk = SystemCoreClock/8;
	break;
  }

  LPC_TIM0->MR0 = pclk/DATA_FREQ - 1;	/* TC0 Match Value 0 */
  LPC_TIM0->MCR = 3;					/* TCO Interrupt and Reset on MR0 */
  LPC_TIM0->TCR = 1;					/* TC0 Enable */
  NVIC_EnableIRQ(TIMER0_IRQn);

  USB_Init();				/* USB Initialization */
  USB_Connect(TRUE);		/* USB Connect */

  /********* The main Function is an endless loop ***********/
  while( 1 );
}

/******************************************************************************
**                            End Of File
******************************************************************************/
/*
 * @}
 */