MSP430G2x33 VLO calibration without TI library

Hi Rob,

I found this for F series controller , I configured my controller to work at 8 MHz (Clock Settings) at start up but I see in below mentioned code this clock settings are changed to 1 MHz while calculating VLO calibration frequency there after I am not able to use my serial port . 

I tried to reset back my controller to 8MHz once I finish reading VLO calibration but now nothing is working . Any clue?

#include <msp430x26x.h>

unsigned int dco_delta;

// Function Prototype
unsigned int  measureVLO( void );

void main(void)
{
  WDTCTL = WDTPW +WDTHOLD;                  // Stop Watchdog Timer
  P1DIR |= 0x01;                            // P1.0 output
 
  dco_delta = measureVLO();                 // dco delta = number of
                                            // 1MHz cycles in 8 VLO cycles
  //Clock settings: DCO freq = 1MHz; ACLK = VLO/8
 
  // Timer A interval interrupt setup
  TACCTL0 = CCIE;                           // TACCR0 interrupt enabled
  TACCR0 = (1000000 / dco_delta);             
  TACTL = TASSEL_1 + MC_1;                  // ACLK, upmode
  P1OUT = 0x01;
 
  _BIS_SR(LPM3_bits + GIE);                 // Enter LPM3 w/ interrupt

}

// Timer_A0 Interrupt Vector
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A0(void)
{
  P1OUT ^= 0x01;                            // Toggle P1.0
}

// This function measures the number of 1MHz clock pulses in 8 VLO cycles
unsigned int  measureVLO( void )
{
  static unsigned int start_count, stop_count;
  // Clock settings to achieve the good resolution for VLO freq measurement
  BCSCTL1 = CALBC1_1MHZ;                    // Set range
  DCOCTL = CALDCO_1MHZ;                     // Set DCO step + modulation
  TACCTL2 = CM_1+CCIS_1+CAP;                // CAP, ACLK
  TACTL = TASSEL_2+MC_2+TACLR;              // SMCLK, cont-mode, clear
  BCSCTL3 |= LFXT1S_2;                      // ACLK = VLO  
  BCSCTL2 = 0x0;
  BCSCTL1 |= DIVA_3;                        // ACLK = VLO/8
 
  TACCTL2 &= ~CCIFG;                        // Clear capture flag
  while (!(CCIFG & TACCTL2));               // Test capture flag to skip 1st cycle
  TACCTL2 &= ~CCIFG;                        // Clear capture flag
 
  while (!(CCIFG & TACCTL2));               // Test capture flag to skip 2nd cycle
  start_count = TACCR2;                     // save hardware captured value
  TACCTL2 &= ~CCIFG;                        // Clear capture flag
 
  while (!(CCIFG & TACCTL2));               // Test capture flag to capture a good clock
  TACTL &= ~MC_3;                           // Stop timer
  stop_count = TACCR2;
  return(stop_count - start_count);         // return
}

Hi Raj,

I can't see anything obvious in that code which would cause problems with serial output. It appears to just be a direct translation of TI's library code into C (except it lacks the clean-up steps which restore the original clock settings on function exit).

Would you mind posting the rest of your code so we can see if anything might be affected by the calibration function?

Rob

Hi Rob,

I just verified , it is this piece of code which is not working and controller is getting hanged. I think this code doesn't work for MSP430G2xx3 based controllers.

TACCTL2 = CM_1+CCIS_1+CAP;                // CAP, ACLK
  TACTL = TASSEL_2+MC_2+TACLR;              // SMCLK, cont-mode, clear
  BCSCTL3 |= LFXT1S_2;                      // ACLK = VLO  
  BCSCTL2 = 0x0;
  BCSCTL1 |= DIVA_3;                        // ACLK = VLO/8
 
  TACCTL2 &= ~CCIFG;                        // Clear capture flag
  while (!(CCIFG & TACCTL2));               // Test capture flag to skip 1st cycle
  TACCTL2 &= ~CCIFG;                        // Clear capture flag
 
  while (!(CCIFG & TACCTL2));               // Test capture flag to skip 2nd cycle
  start_count = TACCR2;                     // save hardware captured value
  TACCTL2 &= ~CCIFG;                        // Clear capture flag
 
  while (!(CCIFG & TACCTL2));               // Test capture flag to capture a good clock
  TACTL &= ~MC_3;                           // Stop timer
  stop_count = TACCR2;
  return(stop_count - start_count);         // return

Hi Rob,

I debugged this issue and I see controller is not able to come out of while loop , it is stuck there without any response.

I referred MSP430G2x33 datasheet and I don't see anything wrong in this code but I am not sure why it is hanging out there.

   TACCTL1 &= ~CCIFG;                        // Clear capture flag
    while (!(CCIFG & TACCTL1));               // Test capture flag to skip 1st cycle
    TACCTL1 &= ~CCIFG;                        // Clear capture flag

Hi Robert,

You were right, TA0CCTL0 should be used for ACLK measurement, now code works but I am not getting 1 sec interrupt instead it is around 400 to 900ms which is not stable . Below is my code for your reference.

#include <msp430g2333.h>

unsigned int dco_delta;
// Function Prototype
unsigned int  measureVLO( void );

void main()
{

    /* Stop WDT */
    WDTCTL  =  WDTPW | WDTHOLD;
    /*
        8 MHz Clock settings for UART
    */
    
    BCSCTL1 |= DIVA0;                     // ACLK/1
    BCSCTL2 |= SELM_0 + DIVM_0;          // MCLK = DCOCLK , DIVISOR= /1 (8MHZ)
    BCSCTL3 |= LFXT1S_2;                  // Low frequency clock selector
    
    dco_delta = measureVLO();      
    CCTL0 = CCIE;                                // TACCR0 interrupt enabled
    CCR0  = (8000000 / dco_delta);            // Timer clock delta with VLO calibration
    TACTL = TASSEL_1 + MC_1;                  // ACLK, upmode
    
    _enable_interrupts();
    
    
     _BIS_SR(LPM3_bits + GIE);                 // Enter LPM3 w/ interrupt
}


#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A (void)
{
    P2OUT ^= LED;    
}


unsigned int measureVLO(void)
{
  static unsigned int start_count, stop_count;
//  Clock settings to achieve the good resolution for VLO freq measurement
  IFG1 &= ~OFIFG;                              // Clear OSCFault flag
  BCSCTL1 = CALBC1_1MHZ;                    // Set range
  DCOCTL  = CALDCO_1MHZ;                     // Set DCO step + modulation
  if (CALBC1_1MHZ == 0xFF)                    // If calibration constant erased
  {
         while(1);                           // do not load, trap CPU!!
  }
 
    P2OUT &= ~LED;
    P2DIR |= LED;

    TACCTL0 = CM_1+ CCIS_1+ CAP;              // CAP, ACLK
    TACTL = TASSEL_2+MC_2+TACLR;              // SMCLK, cont-mode, clear
    BCSCTL3 |= LFXT1S_2;                      // ACLK = VLO
    BCSCTL2 = 0x0;
    BCSCTL1 |= DIVA_3;                        // ACLK = VLO/8

    TACCTL0 &= ~CCIFG;                        // Clear capture flag
    while (!(CCIFG & TACCTL0));               // Test capture flag to skip 1st cycle
    TACCTL0 &= ~CCIFG;                        // Clear capture flag

    while (!(CCIFG & TACCTL0));               // Test capture flag to skip 2nd cycle
    start_count = TACCR2;                     // save hardware captured value
    TACCTL0 &= ~CCIFG;                        // Clear capture flag

    while (!(CCIFG & TACCTL0));               // Test capture flag to capture a good clock
    TACTL &= ~MC_3;                           // Stop timer
    stop_count = TACCR0;

    TACCTL0 = 0;                              // Stop TACCR0
    TACTL = 0;                                // Stop Timer_A
    
    /*
        RESTORE BACK DEFAULT CALIBRATION SETTINGS
    */
    BCSCTL1 =  CALBC1_8MHZ;            // Run at 8 MHz
    DCOCTL  =  CALDCO_8MHZ;            // Run at 8 MHz
    if (CALBC1_8MHZ==0xFF)                        // If calibration constant erased
      {
        while(1);                               // do not load, trap CPU!!
      }
    BCSCTL1 |= DIVA0;                     // ACLK/1
    BCSCTL2 |= SELM_0 + DIVM_0;          // MCLK = DCOCLK , DIVISOR= /1 (8MHZ)
    BCSCTL3 |= LFXT1S_2;                  // Low frequency clock selector


    return(stop_count - start_count);         // return

}