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Original question:

CCS/TM4C1294NCPDT: TM4C1294 ADC sample problems

CCS/TM4C1294NCPDT: TM4C1294 ADC sample problems

Jagriti Hirwani
Prodigy 70 points
Part Number: TM4C1294NCPDT


Tool/software: Code Composer Studio

how to change the sample rate of adc to get high frequency signals

  • 0
    TI__Guru*** 135355 points
    Hello Jagriti,

    What sample rate are you currently at? Can you share your ADC configuration code? What sample rate are you seeking to achieve?
  • 0 in reply to Ralph Jacobi
    Prodigy 70 points
    SysCtlPeripheralEnable(SYSCTL_PERIPH_ADC0);
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOE);
    GPIOPinTypeADC(GPIO_PORTE_BASE, GPIO_PIN_3);
    ADCSequenceConfigure(ADC0_BASE, 3, ADC_TRIGGER_PROCESSOR, 0);
    ADCSequenceStepConfigure(ADC0_BASE, 3, 0, ADC_CTL_CH0 |
    ADC_CTL_IE | ADC_CTL_END);
    ADCSequenceEnable(ADC0_BASE, 3);
    ADCIntClear(ADC0_BASE, 3);

    while(1)
    {

    ADCProcessorTrigger(ADC0_BASE, 3);
    while(!ADCIntStatus(ADC0_BASE, 3, false)) // ---> program stuck HERE
    {
    }
    ADCIntClear(ADC0_BASE, 3);
    ADCSequenceDataGet(ADC0_BASE, 3, pui32ADC0Value);
    analog_value=pui32ADC0Value[0];

    }
    this is the adc configuration code.
    but i can only sample signals of very low frequency around 100 mHz.
  • 0 in reply to Jagriti Hirwani
    TI__Guru*** 135355 points

    Hello Jagriti,

    Thank you for sharing the code and current sampling ability, can you please also explain what frequency you are wanting to sample so I can help describe what needs to be done to increase the sampling rate to meet your needs?

  • 0 in reply to Ralph Jacobi
    Prodigy 70 points
    hello,

    I am trying to sample signals in Kiloherts to megahertz frequency.
  • 0 in reply to Jagriti Hirwani
    TI__Guru*** 135355 points
    Hello Jagriti,

    Thank you! kHz frequency sampling is no problem, MHz will be much harder unless you mean just around 1MHz. The ADC is capped at 2MSPS, so you have a limitation from that standpoint.

    In general, you want to use a timer and have the ADC sampling trigger based on the timer rather than using the ADCProcessorTrigger API.

    To get the maximum ADC sampling speed, you should refer to this post where Bob shared source code for getting 2MSPS working: e2e.ti.com/.../2544084

    Bob's code shows how to configure the Timer as well as the ADC for ADC sampling on timer interrupt, so even if you end up not going for the 2MSPS method, you can leverage his example code to add in the timer operation that will help increase your sampling frequency.
  • 0 in reply to Ralph Jacobi
    Prodigy 70 points

    Hello,

    Thankyou so much, I will try to trigger the ADC using timer.