This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

timer A for microseconds.

Other Parts Discussed in Thread: MSP430G2553

I need a timer_A generating interrupting each 130 microseconds, but look like that he hangs in the loop. Well, if i elevate the interval the software does what i want. Enter in interrup, add a value in queue type FIFO, exits, remove and shows this value. If i put interval in microseconds he hangs. How i can have this interval working?

i am using msp430g2553

  • felipe paulo said:
    ...  Enter in interrup, add a value in queue type FIFO, exits, remove and shows this value...

    If the above takes more than 130 microseconds, then the next interrupts will be requested before the previous one is handled. Interrupt will pile up or mess-up. Stack and FIFO might overflow.

    How fast is the CPU running? How much can it do within 130 microsecond?

  • CPU running 1MHz.

    in interrupting he gets a sample of ADC,  add in FIFO and verify if the loop was run 128 times

    the timer are as configured:

      CCTL0 = CCIE;
      CCR0 = 130;
      TACTL = TASSEL_2 + MC_1;   

  • felipe paulo said:
    ... in interrupting he gets a sample of ADC,  add in FIFO and verify if the loop was run 128 times ...

    That probably will take more then 130 MCLK.

    Try set MCLK to 8 MHz and keep SMCLK at 1 MHz

  •   BCSCTL1 = CALBC1_8MHZ;
      DCOCTL = CALDCO_8MHZ;
      BCSCTL2 = DIVS_3;

    I set up like this?

  • is almost solved the problem. Put 130 microseconds in timer e then exit, it worked. But now i trying do in the timer, a ADC converter, but he don´t want leave the interrupt.

      BCSCTL1 = CALBC1_8MHZ; //MCLK = 8MHZ
      DCOCTL = CALDCO_8MHZ;
      BCSCTL3 = DIVS_3;   //SMCLK = 8MHZ/8=1MHZ
     
      ADC10CTL1 = INCH_7 + CONSEQ_1;            // A2/A1/A0, single sequence
      ADC10CTL0 = ADC10SHT_2 + MSC + ADC10ON + ADC10IE;
      ADC10DTC1 = 0x03;                         // 3 conversions
      ADC10AE0 |= 0xC0;                         // P1.7,6 ADC10 option select
     
        InitLCD();  //Inica o LCD
        LCDClear(); //Limpa a tela
      __enable_interrupt();  //Habilita interrupções


      TACCTL0 = CCIE;                           // TACCR0 interrupt enabled
      TACCR0 = 16;            //Ciclos de SMCLK
      TACTL = TASSEL_2   MC_1   ID_3;                  // SMCLK/8 = 125Khz, upmode
      LPM0;   //Entra em MODO low power mode 0
      LCDSetPosition(0,0); //Define posição
      printDecimal(points); //Exibe a variável pontos
    }

    // Timer A0 interrupt service routine
    #pragma vector=TIMER0_A0_VECTOR
    __interrupt void Timer_A (void)
    {

        ADC10CTL0 &= ~ENC;
        while (ADC10CTL1 & BUSY);               // Wait if ADC10 core is active
        ADC10SA = (unsigned int)&conv_ADC10;    // Inicializa o buffer de dados
        ADC10CTL0 |= ENC   ADC10SC;             // Inicia a amostragem/conversão
     
    }
     
    // ADC10 interrupt service routine
    #pragma vector=ADC10_VECTOR
    __interrupt void ADC10_ISR(void)
    {    
      while (ADC10CTL1 & BUSY);
      points++; //Increment points for me know how many times the timer was executed
                //if was executed 150 times, he leave of interrupt, get the values and show in LCD.
      if(points == 150){
      LPM0_EXIT;
      }
    }


    but does not work

  • if I put the TIMER with ACLK instead of SMCLK could be even faster?
    Why Are the SMCLK 1MHZ he does not do what I gotta do this time with this range.



  • felipe paulo said:
        while (ADC10CTL1 & BUSY);               // Wait if ADC10 core is active

    This kind of statement ha sno place inside an ISR. It will execute for an indeterminate length. And since an ISR cannot interrupt anotehr ISR, this may lock-up the whole system.

    ISRs are fast-in and should be fast-out too. No waiting inside. The ISR is called when something happens, to immediately react on the event. They are definitely not meant to wait until something happens.

    Independent of that, ENC does not start the conversion. ADC10SC starts it. (SC for Start Conversion). ENC is just enabling or disabling the encoder (e.g. to emergency-stop a sequence)

    Finally, ADC10_VECTOR is called whenever a conversion is done. So if it is called, you know for sure that a conversion was done, and a result is ready. So you should copy the content here and not in the timer ISR.

    IN the tiemr ISR, there are two cases: either the sequence is ready when teh timer expires. Then it is superfluous to wait for the ADC: it's done and you only need to set ADC10SC again to start the next sequence. Or it isn't done. In this case your timer is too fast. Always. I tmakes no sense to wait for the ADC then, as you'll have to always wait. Since the ADC requires always the same tiemr for a sequence. You must either speed up the ADC by selecting a different SHTx or slow down the timer.
    Which one happens should be obvious after a little elementary school math.

**Attention** This is a public forum