TMS320F280039C: Clarification on ADC Interrupt Timing in TMS320F280039C

Hi Prathamesh,

Appologies for late reply. Can you share the C code snippet for the above mentioned code (that will be easier to decode)  ?

BR,

Nilesh

Also what is the value of ACQPS kept for this configuration ?

/*
 * Modifications made by Prathamesh on 28th July, 2025:
 *
 * 1. Removed storage of ADC results in a 256-value buffer.
 * 2. Removed CPU halt and reset logic.
 * 3. Implemented continuous ADC result reading within the ADC ISR.
 *
 * Additional Notes:
 * - ADC is triggered at TBCTR zero value.
 * - Upon completion of ADC SOC/EOC, an interrupt is generated.
 * - Observed ADC conversion time is approximately 1 µs.
 *
 * Date: 29th July 2025
 * Learned that ADC interrupt was incorrectly configured—triggered
 * at SOC0 instead of final SOCN (where N = 1, 2, 3, ..., N).
 * Each SOC takes ~30 PWM counts, which equals ~250 ns (30 × 8.33 ns).
 * Raised a TI E2E forum query to understand why an additional ~500 ns delay
 * occursfor the first SOC0.
 */
 void main(void)
{
    //
    // Initialize device clock and peripherals
    //
    Device_init();

    //
    // Disable pin locks and enable internal pullups.
    //
    Device_initGPIO();

    //
    // Initialize PIE and clear PIE registers. Disables CPU interrupts.
    //
    Interrupt_initModule();

    //
    // Initialize the PIE vector table with pointers to the shell Interrupt
    // Service Routines (ISR).
    //
    Interrupt_initVectorTable();

    // 
    // Board Initialization
    // - Set up the ADC and initialize the SOC
    // - Enable ADC interrupt
    //
    Board_init();

    //
    // Enable Global Interrupt (INTM) and realtime interrupt (DBGM)
    //
    EINT;
    ERTM;

    //
    // Loop indefinitely
    //
    while(1)
    {

    }
}

//
// adcA1ISR - ADC A Interrupt 1 ISR
//
__interrupt void adcA1ISR(void)
{
    isrTick_Entry = EPWM_getTimeBaseCounterValue(myEPWM0_BASE);

    GPIO_togglePin(myGPIO0);
//    isrTick_Exist = EPWM_getTimeBaseCounterValue(myEPWM0_BASE);


    //
    // Add the latest result to the buffer
    //
    myADC0Results = ADC_readResult(ADCARESULT_BASE, ADC_SOC_NUMBER0);
    myADC1Results = ADC_readResult(ADCBRESULT_BASE, ADC_SOC_NUMBER0);

    //
    // Clear the interrupt flag
    //
    ADC_clearInterruptStatus(myADC0_BASE, ADC_INT_NUMBER1);

    //
    // Acknowledge the interrupt
    //
    Interrupt_clearACKGroup(INT_myADC0_1_INTERRUPT_ACK_GROUP);
}

void myADC0_init(){
	//
	// ADC Initialization: Write ADC configurations and power up the ADC
	//
	// Set the analog voltage reference selection and ADC module's offset trims.
	// This function sets the analog voltage reference to internal (with the reference voltage of 1.65V or 2.5V) or external for ADC
	// which is same as ASysCtl APIs.
	//
	ADC_setVREF(myADC0_BASE, ADC_REFERENCE_INTERNAL, ADC_REFERENCE_3_3V);
	//
	// Configures the analog-to-digital converter module prescaler.
	//
	ADC_setPrescaler(myADC0_BASE, ADC_CLK_DIV_2_0);
	//
	// Sets the timing of the end-of-conversion pulse
	//
	ADC_setInterruptPulseMode(myADC0_BASE, ADC_PULSE_END_OF_ACQ_WIN);
	//
	// Sets the timing of early interrupt generation.
	//
	ADC_setInterruptCycleOffset(myADC0_BASE, 0U);
	//
	// Powers up the analog-to-digital converter core.
	//
	ADC_enableConverter(myADC0_BASE);
	//
	// Delay for 1ms to allow ADC time to power up
	//
	DEVICE_DELAY_US(5000);
	//
	// SOC Configuration: Setup ADC EPWM channel and trigger settings
	//
	// Disables SOC burst mode.
	//
	ADC_disableBurstMode(myADC0_BASE);
	//
	// Sets the priority mode of the SOCs.
	//
	ADC_setSOCPriority(myADC0_BASE, ADC_PRI_THRU_SOC1_HIPRI);
	//
	// Start of Conversion 0 Configuration
	//
	//
	// Configures a start-of-conversion (SOC) in the ADC and its interrupt SOC trigger.
	// 	  	SOC number		: 0
	//	  	Trigger			: ADC_TRIGGER_EPWM1_SOCA
	//	  	Channel			: ADC_CH_ADCIN0
	//	 	Sample Window	: 9 SYSCLK cycles
	//		Interrupt Trigger: ADC_INT_SOC_TRIGGER_NONE
	//
	ADC_setupSOC(myADC0_BASE, ADC_SOC_NUMBER0, ADC_TRIGGER_EPWM1_SOCA, ADC_CH_ADCIN0, 9U);
	ADC_setInterruptSOCTrigger(myADC0_BASE, ADC_SOC_NUMBER0, ADC_INT_SOC_TRIGGER_NONE);
	//
	// Start of Conversion 1 Configuration
	//
	//
	// Configures a start-of-conversion (SOC) in the ADC and its interrupt SOC trigger.
	// 	  	SOC number		: 1
	//	  	Trigger			: ADC_TRIGGER_EPWM1_SOCA
	//	  	Channel			: ADC_CH_ADCIN1
	//	 	Sample Window	: 9 SYSCLK cycles
	//		Interrupt Trigger: ADC_INT_SOC_TRIGGER_NONE
	//
	ADC_setupSOC(myADC0_BASE, ADC_SOC_NUMBER1, ADC_TRIGGER_EPWM1_SOCA, ADC_CH_ADCIN1, 9U);
	ADC_setInterruptSOCTrigger(myADC0_BASE, ADC_SOC_NUMBER1, ADC_INT_SOC_TRIGGER_NONE);
	//
	// Start of Conversion 2 Configuration
	//
	//
	// Configures a start-of-conversion (SOC) in the ADC and its interrupt SOC trigger.
	// 	  	SOC number		: 2
	//	  	Trigger			: ADC_TRIGGER_EPWM1_SOCA
	//	  	Channel			: ADC_CH_ADCIN2
	//	 	Sample Window	: 9 SYSCLK cycles
	//		Interrupt Trigger: ADC_INT_SOC_TRIGGER_NONE
	//
	ADC_setupSOC(myADC0_BASE, ADC_SOC_NUMBER2, ADC_TRIGGER_EPWM1_SOCA, ADC_CH_ADCIN2, 9U);
	ADC_setInterruptSOCTrigger(myADC0_BASE, ADC_SOC_NUMBER2, ADC_INT_SOC_TRIGGER_NONE);
	//
	// Start of Conversion 3 Configuration
	//
	//
	// Configures a start-of-conversion (SOC) in the ADC and its interrupt SOC trigger.
	// 	  	SOC number		: 3
	//	  	Trigger			: ADC_TRIGGER_EPWM1_SOCA
	//	  	Channel			: ADC_CH_ADCIN3
	//	 	Sample Window	: 9 SYSCLK cycles
	//		Interrupt Trigger: ADC_INT_SOC_TRIGGER_NONE
	//
	ADC_setupSOC(myADC0_BASE, ADC_SOC_NUMBER3, ADC_TRIGGER_EPWM1_SOCA, ADC_CH_ADCIN3, 9U);
	ADC_setInterruptSOCTrigger(myADC0_BASE, ADC_SOC_NUMBER3, ADC_INT_SOC_TRIGGER_NONE);
	//
	// ADC Interrupt 1 Configuration
	// 		Source	: ADC_SOC_NUMBER3
	// 		Interrupt Source: enabled
	// 		Continuous Mode	: disabled
	//
	//
	ADC_setInterruptSource(myADC0_BASE, ADC_INT_NUMBER1, ADC_SOC_NUMBER3);
	ADC_clearInterruptStatus(myADC0_BASE, ADC_INT_NUMBER1);
	ADC_disableContinuousMode(myADC0_BASE, ADC_INT_NUMBER1);
	ADC_enableInterrupt(myADC0_BASE, ADC_INT_NUMBER1);
}
void myADC1_init(){
	//
	// ADC Initialization: Write ADC configurations and power up the ADC
	//
	// Set the analog voltage reference selection and ADC module's offset trims.
	// This function sets the analog voltage reference to internal (with the reference voltage of 1.65V or 2.5V) or external for ADC
	// which is same as ASysCtl APIs.
	//
	ADC_setVREF(myADC1_BASE, ADC_REFERENCE_INTERNAL, ADC_REFERENCE_3_3V);
	//
	// Configures the analog-to-digital converter module prescaler.
	//
	ADC_setPrescaler(myADC1_BASE, ADC_CLK_DIV_2_0);
	//
	// Sets the timing of the end-of-conversion pulse
	//
	ADC_setInterruptPulseMode(myADC1_BASE, ADC_PULSE_END_OF_ACQ_WIN);
	//
	// Sets the timing of early interrupt generation.
	//
	ADC_setInterruptCycleOffset(myADC1_BASE, 0U);
	//
	// Powers up the analog-to-digital converter core.
	//
	ADC_enableConverter(myADC1_BASE);
	//
	// Delay for 1ms to allow ADC time to power up
	//
	DEVICE_DELAY_US(5000);
	//
	// SOC Configuration: Setup ADC EPWM channel and trigger settings
	//
	// Disables SOC burst mode.
	//
	ADC_disableBurstMode(myADC1_BASE);
	//
	// Sets the priority mode of the SOCs.
	//
	ADC_setSOCPriority(myADC1_BASE, ADC_PRI_ALL_ROUND_ROBIN);
	//
	// Start of Conversion 0 Configuration
	//
	//
	// Configures a start-of-conversion (SOC) in the ADC and its interrupt SOC trigger.
	// 	  	SOC number		: 0
	//	  	Trigger			: ADC_TRIGGER_EPWM1_SOCA
	//	  	Channel			: ADC_CH_ADCIN0
	//	 	Sample Window	: 9 SYSCLK cycles
	//		Interrupt Trigger: ADC_INT_SOC_TRIGGER_NONE
	//
	ADC_setupSOC(myADC1_BASE, ADC_SOC_NUMBER0, ADC_TRIGGER_EPWM1_SOCA, ADC_CH_ADCIN0, 9U);
	ADC_setInterruptSOCTrigger(myADC1_BASE, ADC_SOC_NUMBER0, ADC_INT_SOC_TRIGGER_NONE);
}

//*****************************************************************************
//
// EPWM Configurations
//
//*****************************************************************************
void EPWM_init(){
    EPWM_setEmulationMode(myEPWM0_BASE, EPWM_EMULATION_FREE_RUN);	
    EPWM_setClockPrescaler(myEPWM0_BASE, EPWM_CLOCK_DIVIDER_1, EPWM_HSCLOCK_DIVIDER_1);	
    EPWM_setTimeBasePeriod(myEPWM0_BASE, 1999);	
    EPWM_setTimeBaseCounter(myEPWM0_BASE, 0);	
    EPWM_setTimeBaseCounterMode(myEPWM0_BASE, EPWM_COUNTER_MODE_UP);	
    EPWM_disablePhaseShiftLoad(myEPWM0_BASE);	
    EPWM_setPhaseShift(myEPWM0_BASE, 0);	
    EPWM_setCounterCompareValue(myEPWM0_BASE, EPWM_COUNTER_COMPARE_A, 1000);	
    EPWM_setCounterCompareShadowLoadMode(myEPWM0_BASE, EPWM_COUNTER_COMPARE_A, EPWM_COMP_LOAD_ON_CNTR_ZERO);	
    EPWM_setCounterCompareValue(myEPWM0_BASE, EPWM_COUNTER_COMPARE_B, 0);	
    EPWM_setCounterCompareShadowLoadMode(myEPWM0_BASE, EPWM_COUNTER_COMPARE_B, EPWM_COMP_LOAD_ON_CNTR_ZERO);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_PERIOD);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPB);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_A, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPB);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_LOW, EPWM_AQ_OUTPUT_ON_TIMEBASE_ZERO);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_PERIOD);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_HIGH, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPA);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPA);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_UP_CMPB);	
    EPWM_setActionQualifierAction(myEPWM0_BASE, EPWM_AQ_OUTPUT_B, EPWM_AQ_OUTPUT_NO_CHANGE, EPWM_AQ_OUTPUT_ON_TIMEBASE_DOWN_CMPB);	
    EPWM_setRisingEdgeDelayCountShadowLoadMode(myEPWM0_BASE, EPWM_RED_LOAD_ON_CNTR_ZERO);	
    EPWM_disableRisingEdgeDelayCountShadowLoadMode(myEPWM0_BASE);	
    EPWM_setFallingEdgeDelayCountShadowLoadMode(myEPWM0_BASE, EPWM_FED_LOAD_ON_CNTR_ZERO);	
    EPWM_disableFallingEdgeDelayCountShadowLoadMode(myEPWM0_BASE);	
    EPWM_enableADCTrigger(myEPWM0_BASE, EPWM_SOC_A);	
    EPWM_setADCTriggerSource(myEPWM0_BASE, EPWM_SOC_A, EPWM_SOC_TBCTR_ZERO);	
    EPWM_setADCTriggerEventPrescale(myEPWM0_BASE, EPWM_SOC_A, 1);	
}

Hi Nilesh,

Thank you for your reply.

I am attaching the code, and I keep ACQPS value equal to '9'.

BRs,

Prathamesh.

Hi Prathamesh,

Let me go throught the code trying to see if i can replicate the issue on my side will update over the weekend. 

BR,

Nilesh