Capture ADC values on a continuous basis

One way is to use another interrupt to auto trigger the adc.   This could be either a timer or or interrupt of an external input (like an encoder or external clock)

In my case I was firing the a2d via an external encoder input  but you could easily make it a timer.  I did this on a 2808.

interrupt void timer_isr(void)  <- could also be "interrupt void xint1_isr(void)"  if an encoder or external clock input.
{   
    AdcRegs.ADCTRL2.bit.SOC_SEQ1 = 1;// Toggle bit to initiate Start of Capture on ADC
    // Acknowledge this interrupt to get more from group 1
    PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
}

interrupt void  adc_isr(void)
{

    //grab the samples
    samplea=((AdcRegs.ADCRESULT0 >> 4) - 2048);
    sampleb=((AdcRegs.ADCRESULT1 >> 4) - 2048);//and now read & correct actual

    // Reinitialize for next ADC sequence
    AdcRegs.ADCTRL2.bit.RST_SEQ1 = 1;         // Reset SEQ1
    AdcRegs.ADCST.bit.INT_SEQ1_CLR = 1;       // Clear INT SEQ1 bit

    PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;   // Acknowledge interrupt to PIE
    return;
}

My understanding is that the ADC value is not correct until it is done measuring the input.  While the timer starts the ADC, what triggers the ISR when the ADC is done?

In the situation I described above the triggering interval was much slower than the a/d conversion time, so it was not a concern.

You will need to set the interrupt enable for SEQ1 if you are using your example.  This will be the source of your ADC interrupt to the PIE.

Secondly, the ADC ISR will need to clear the SEQ1 interrupt flag in the ADC to re-arm the interrupt for the next conversion sequence.

An example of this is in the C280x, C2801x C/C++ Header Files and Peripheral Examples in the <INSTALL_DIR>\tidcs\c28\DSP280x\v170\DSP280x_examples_ccsv4\adc_soc example.

I have read the SPRU doc and reviewed the example code.  Exactly, what code changes should be added / modified?

The code example that I highlighted in the previous post has the line in it to enable the SEQ1 interrupt from the ADC to propagate to the PIE.

Upon adding this line of code to your own application, what results do you get?  Are you getting interrupts now after the sequence of ADC conversions?

I don't know what code you highlighted ... don't see any highlighting.  Interrupts do not occur.  What needs to be set for ADCINT to interrupt?

See post dated Mon, Feb 28 2011 10:18 PM.

The example which I pointed out (perhaps highlighted was a misleading term) provides an illustration of enabling the SEQ1 interrupt and clearing the appropriate status flag in the interrupt service routine.

Please post a snippet of code that would work with the code I posted three day ago.

The example has code that is not relevant.  Thanks for listing the code that is relevant.

Unfortunately, it still does not work.  While the interrupts are occurring, the data is always 2048 (after shifting it to the right four places) ... I am changing the voltage to AdcIna0 from 0v to 0.2v.  Here is my code:

//-----------------------------------------------------------------------------
interrupt void IsrAdc(void)
{
  uiAdcValue = (AdcRegs.ADCRESULT0 >> 4);

  AdcRegs.ADCTRL2.bit.RST_SEQ1 = 1;        
  AdcRegs.ADCST.bit.INT_SEQ1_CLR = 1;      
  PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
}//IsrAdc
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
void gInitAdc(void)
{
  EALLOW;
  PieVectTable.ADCINT = &IsrAdc;
  EDIS;
  IER |= M_INT1;
  PieCtrlRegs.PIEIER1.bit.INTx6 = 1;

  AdcRegs.ADCCHSELSEQ1.bit.CONV00 = 0;
  AdcRegs.ADCTRL1.bit.CONT_RUN = 1;
}//gInitAdc
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
void gStartAdc(void)
{
  AdcRegs.ADCTRL2.bit.SOC_SEQ1 = 1;
  AdcRegs.ADCTRL2.bit.INT_ENA_SEQ1 = 1;
}//gStartAdc
//-----------------------------------------------------------------------------

Clyde,

In my case (where I was triggering the adc through an external interrupt) I was only using two adc channels so I had initialized them accordingly.

AdcRegs.ADCTRL3.all = 0x00E0;
//11100000
//which is band gap ref circ power up, adc powerup
//and core clock divider = 0 = HSPCLK

AdcRegs.ADCTRL1.bit.CPS=1;  //divde HSPCLK by 2
//if we don't do the above the adc clock runs too fast
//and we get single bit errors in the data.

AdcRegs.ADCMAXCONV.all = 0x0001;       // Setup 2 conv's on SEQ1
AdcRegs.ADCCHSELSEQ1.bit.CONV00 = 0x0; // Setup ADCINA1 as 1st SEQ1 conv.
AdcRegs.ADCCHSELSEQ1.bit.CONV01 = 0x1; // Setup ADCINA0 as 2nd SEQ1 conv.

Not sure if the above is applicable to your situation but might help.