ADC query; tm4c123gxl laucnhpad; internal temperature sensor

Other Parts Discussed in Thread: TM4C123GH6PM

1. I have made adc code using sample sequencer 3. using keil 5.13.0.0 & driverlib 2.1.1.71.

2.In ADCClockConfigSet, what is the purpose of ADC_CLOCK_RATE_FULL,

ADCClockConfigSet(ADC0_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL, 25U);

This function write 0x07 to register ADCSPC (page 844 of tm4c123gh6pm datasheet) which means "ADC sample lags by 157.5°".

What does that mean & how does it make clock rate full.

3. Page 38 of peripheral driver library says that, if ADCReferenceSet is used with ADC_REF_INT then reference is 3V.

However datasheet of MCU says that its 3.3V (voltage at Vdda & vssa). So i think its 3.3V right?

4. I took 100 samples of Internal temperature sensor, ignoring first two samples, the difference between max & min values is around 6 degree. Is it ok to have this large difference. Although datsheet says accuracy could be +-5C. But does that mean samples taken at a time could have such large variation.

Range is 30 to 35.5.

Edit: When turn on debug option goes into error in function ADCClockConfigSet(ADC0_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL, 25U);

In this function error pint is :

ASSERT(((ui32ClockDiv - 1) & (ADC_CC_CLKDIV_M >> ADC_CC_CLKDIV_S)) == 0);

The left hand expression comes out to be 0x180 & code into error.

5. Below is my code. Are the steps to configure adc are correct:

    uint32_t ready_count;
    uint32_t pui32ADC0Value[1];
    uint32_t temp_c;

/* enable adc0 */    
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    while( (!(SysCtlPeripheralReady(SYSCTL_PERIPH_ADC0)))  &&  (--ready_count));
    if(0U == ready_count)   /* if periph not ready take action */
    {
    }    
    
    
/* disable any sequence, over-under flow, int before setting parasmeters of adc  */
    ADCSequenceDisable(ADC0_BASE , 3U);
    ADCSequenceOverflowClear(ADC0_BASE , 3U);
    ADCSequenceUnderflowClear(ADC0_BASE , 3U);
    ADCIntDisable(ADC0_BASE , 3U);
    ADCIntClear(ADC0_BASE , 3U);
    ADCComparatorIntDisable(ADC0_BASE , 3U);
    ADCComparatorIntClear(ADC0_BASE , 3U);
    ADCSequenceDMADisable(ADC0_BASE , 3U);
    
/* set clock & other functions */
    ADCClockConfigSet(ADC0_BASE, ADC_CLOCK_SRC_PLL | ADC_CLOCK_RATE_FULL, 25U);  
    ADCReferenceSet(ADC0_BASE , ADC_REF_INT);   
    ADCSequenceConfigure(ADC0_BASE, 3U, ADC_TRIGGER_PROCESSOR, 0U);  
    ADCSequenceStepConfigure(ADC0_BASE, 3U, 0U, ADC_CTL_TS | ADC_CTL_IE | ADC_CTL_END);    
    ADCSequenceEnable(ADC0_BASE, 3U);
    
    while(1)
    {
        ADCProcessorTrigger(ADC0_BASE, 3U);
        while(!ADCIntStatus(ADC0_BASE, 3U, false));
        ADCIntClear(ADC0_BASE, 3U);
        ADCSequenceDataGet(ADC0_BASE, 3U, pui32ADC0Value);
        temp_c = (uint32_t)( 147.5f -  ((75U * 3.3f * pui32ADC0Value[0]) / 4096U) );
        
        wait_delay_us(10000);
        
        temp[cnt++] = temp_c;
        
        if(cnt >= 100U)
        {
            while(1);
        }    
        
    }