Forums

any help regarding this................

The 2253 does not have (general purpose) DMA. It does have, however, the DTC for the ADC10, which serves as a purpose-limited DMA.
When using DTC, keep in mind that a data transfer to ram requires MCLK active. So entering LPM1 or below, which will deactivate the DCO, requires some startup time before MCLK can be activated for the transfer. You shouldn't go below LMP0 except if the distance between two samples is significantly longer than the MCLK startup time.

Now about your questions:

1. it depends. You want to wakeup from LPM once a sequence is done. Normally, the ADC10 sets ADC10IFG once a conversion is done. If ADC10IE is also set, your ADC10 ISR will be called, waking teh CPU from LPM if required.

If the DTC is used, an interrupt is generated after a block transfer is competed. So your ISR is called after the four values are written to ram. If you are sure that wakeup and also handlign the four values can be done faster than the completion of th enext conversion, you canuse repeat sequence of channels. If you're not fast enough, the DTC will overwrite the last sequence in ram while you're still workign on it. Then you should use single sequence of channels mode and restart the ADC when you're done. However, this will increase the time between the last sample of one sequence and the first sample of the next sequence. Probably not an issue.

2. see 1. Once DTC is done, ADC10IFG is set. If DTC is used, the ADC10 will not generate ADC10IFG for every individual conversion. (well, the ADC10 will generate the signal, but it is forwarded to the DTC internally then)

3. not 'should', but 'is'. For a DMA transfer, MCLK is used. The clock cycle is used for DMA and not for the CPU. However, in LPM, MCLK is off, so it needs to be reactivated first (done automatically), and in LPM1 and deeper, this might mean reactivating the DCO, with some delay. Worst case, the ADC10 will have the next result before the transfer is done. Which dumps the unwritten last value then.

I HAVE WRITE CODE FOR FOLLOWING TASK. iS IT RIGHT METHOD.

1. SAMPLE A3 TO A0 WITH dma & dtc. PUT VALUES TO RAM ADDRESS 200H-207H.

2. gO TO SLEEP UNTIL CONVERSION COMPLETE

3. WORK WITH THESE VALUES.

4. GO TO SLEEP MODE.

5. WAKE UP & GO TO STEP 1.

(ABOVE STEPS WILL OCCUR IN 2 SEC EACH INCLUDING SLEEP. & WILL BE IN FIELD FOR 3 MONTH CONTINUOUSLY. IS IT RIGHT WAY)

void main(void)
{

    
    ADC10CTL0 = SREF_1 + ADC10SHT_3 + ADC10SR + MSC + ADC10IE;                // ADC10CTL SETTINGS
    ADC10CTL1 = INCH_3  + ADC10SSEL_3 + CONSEQ_3;            // Repeat CHANNEL FROM A3 TO A0
    ADC10AE0 |= 0x0F;                         
      ADC10DTC1 = 0x04;                         // 4 CONVERSION conversions SO THAT RESULT INTO 0X200-0X207h

    for(;;)
    {  
          ADC10CTL0 |= (ADC10ON + REFON);    //turn on ADC
        __delay_cycles(40);             //settling time 30us for reference buffer
                                    // extra time 10us  in case of variations
        get_adc_value(); 

    __bis_SR_register(CPUOFF + GIE);        // LPM0, ADC10_ISR will force exit
    _NOP();
                             

        ADC10CTL0 &= ~(ADC10ON + REFON);             //turn off adc module

     do_some_other_task();
    }

}

void get_adc_value(void)
{
    ADC10CTL0 &= ~ENC;
    while (ADC10CTL1 & BUSY);               // Wait if ADC10 core is active
    ADC10SA = 0x0200;                        // Data buffer start

   ADC10CTL0 |= ENC + ADC10SC;             // Sampling and conversion start
   
}


#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR(void)
{
  __bic_SR_register_on_exit(CPUOFF);        // Clear CPUOFF bit from 0(SR)
}

any help abt dis

I want 2 reduce power consumption to minimum with Vcc=2.5V min. Is this best method with MSP430G2553 or other methods can be done to reduce power.

any help abt dis.............

Aamir Ali

        ADC10CTL0 &= ~(ADC10ON + REFON);             //turn off adc module

You should clear ENC too. You actually cannot clear ADC10ON if ENC is set.
However, unless the additional current is an issue, you should simply leave ADC10ON and REFON set (note that the reference needs some settling time after being switched on).

Besides this, well, the code look sgood, so why do yoou ask? Compile it and try it. And check the results. And if something is not as you expect, tell us what you expected and what you unexpectedly observed instead. The we might be able to see what's going wrong. Please don't abuse this forum as a preventative code validator. :)