MSP430 How to set ADC12 Sampling rate

Hi,

I'm trying to set my ADC to sample at a 40kHz frequency. I saw I should use the timers to do so, so I set the Timer A for 40kHz.

Im not sure if I didn't get to set the timer A in the good way or if its my ADC's configurations that are wrong. The output in Pin 1.0 which I toggle to see the sampling rate is at 27,7kHz...

 Im using IAR.

Could you please get a look into my code and point the errors?

#include  <msp430F2619.h>
#include <msp430.h>
// Global variables
int adc[10] = {0}; //Sets up an array of 10 integers and zero's the values
int avg_adc = 0; int i=0; unsigned int timerCount = 0;

 
// Function prototypes
void adc_Setup();
void adc_Sam10();
 
void main()
{
   WDTCTL = WDTPW + WDTHOLD;   // Stop WDT
          BCSCTL1 = CALBC1_1MHZ;   // Set range  
          DCOCTL = CALDCO_1MHZ;
          BCSCTL2 &= ~(DIVS_3);   // SMCLK = DCO = 1MHz
         
          TACCTL0 = CCIE; //Timer A config
          TACTL = TASSEL_2 + MC_1;
          CCR0 = 25;
         
         
          P5SEL |= BIT5;
          P5DIR |= BIT5;
         
          
          P6SEL |= BIT3;     // ADC input pin P6.3
          P1DIR |= BIT1 
          P1OUT |= BIT1;

          adc_Setup();      // Fucntion call for adc_setup
          
        
          
 
   while(1)
   {       P1OUT ^= BIT1;                //to measure frequence of sampling
            adc_Sam10();  // Function call for adc_samp
                  
                  
   }
}
 
// ADC10 interrupt service routine
#pragma vector=ADC12_VECTOR
__interrupt void ADC12_ISR(void)
{
  __bic_SR_register_on_exit(CPUOFF);        // Clear CPUOFF bit from 0(SR)
}

 
// ADC set-up function
void adc_Setup()
{
        ADC12MCTL0 = INCH_3 + SREF_0;
        ADC12CTL1 = CONSEQ_2 + INCH_3 + CSTARTADD_0 + SHP + SHS1 + ADC12SSEL_0;
        ADC12CTL0 = INCH_3 + ADC12ON + MSC + SHT0_0;

}
 
// ADC sample conversion function
void adc_Sam10()
{
    ADC12CTL0 |= ENC + ADC12SC;  // Enable Conversion and conversion start 
  
   
}