MSP430F4270: Audio Feedthru

Dear all,

I'm trying to do some DSP with the 4270 since it has an A/D and D/A. I have two questions:

1. Is there a good way to synchronize the input and output sample rates?

2. What is the best way to achieve the fastest sampling? i.e., how can I increase the clock going to the A/D and D/A and should I use interrupts?

Here's my code so far:

//*****************************************************************************
//  Audio Feedthru
//
//                MSP430F4270
//            -----------------
//           |                 |
//           |        DAC0/P1.4|--> Analog Out
//           |                 |
//   Vin+ -->|A0+              |
//   Vin- -->|A0-              |
//           |                 |
//           |            VREF |---+
//           |                 |   |
//           |                 |  -+- 100nF
//           |                 |  -+-
//           |                 |   |
//           |            AVss |---+
//
//*****************************************************************************
#include <msp430.h> 
unsigned int result;

int main(void)
{
	WDTCTL = WDTPW | WDTHOLD;	              // stop watchdog timer
	FLL_CTL0 = DCOPLUS + XCAP14PF;            // DCO+ set so freq = xtal x D x N+1

	SD16CTL = SD16REFON+SD16SSEL0;            // 1.2V ref, SMCLK
	SD16CCTL0 |= SD16SNGL+SD16IE+SD16BUF_3 ;  // Single conv, enable interrupt, high impedance
	SD16INCTL0 |= SD16INTDLY_0;               // Interrupt on 4th sample

	unsigned int i;
    for (i = 0; i < 10000; i++);              // Delay for 32 kHz crystal

	__enable_interrupt();                     // Enable general interrupts

	SD16CTL = SD16REFON;                      // 1.2V ref
	DAC12_0CTL = DAC12OPS + DAC12SREF_2 + DAC12IR + DAC12AMP_5 + DAC12ENC;
	                                            // DAC o/p external, Ref Voltage = internal (SD16),
	                                            // O/p Voltage range = 1x ref, Enable conversion
	while(1){
	    DAC12_0DAT = result >> 1;               // Send A/D result to D/A
	    SD16CCTL0 |= SD16SC;                    // Set bit to start A/D conversion
	    __bis_SR_register(LPM0_bits);           // Enter LPM0
	}
}


#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=SD16_VECTOR
__interrupt void SD16ISR(void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(SD16_VECTOR))) SD16ISR (void)
#else
#error Compiler not supported!
#endif
{
  switch (SD16IV)
  {
  case 2:                                   // SD16MEM Overflow
    break;
  case 4:                                   // SD16MEM0 IFG
    result = SD16MEM0;                      // Save CH0 results (clears IFG)
    break;
  }
  __bic_SR_register_on_exit(LPM0_bits);     // Exit LPM0
}

thank you,

Scott