TMS320F28379D: ADC aquisition timing

//###########################################################################
//
// FILE:   adc_soc_epwm_cpu01.c
//
// TITLE:  ADC triggering via epwm for F2837xD.
//
//! \addtogroup cpu01_example_list
//! <h1> ADC ePWM Triggering (adc_soc_epwm)</h1>
//!
//! This example sets up the ePWM to periodically trigger the ADC.
//!
//! After the program runs, the memory will contain:\n
//! - \b AdcaResults \b: A sequence of analog-to-digital conversion samples from
//! pin A0. The time between samples is determined based on the period
//! of the ePWM timer.
//
//###########################################################################
//
// $Release Date: 10-06-2021 $
// $Copyright:
// Copyright (C) 2013-2021 Texas Instruments Incorporated - http://www.ti.com/
//
// Redistribution and use in source and binary forms, with or without 
// modification, are permitted provided that the following conditions 
// are met:
// 
//   Redistributions of source code must retain the above copyright 
//   notice, this list of conditions and the following disclaimer.
// 
//   Redistributions in binary form must reproduce the above copyright
//   notice, this list of conditions and the following disclaimer in the 
//   documentation and/or other materials provided with the   
//   distribution.
// 
//   Neither the name of Texas Instruments Incorporated nor the names of
//   its contributors may be used to endorse or promote products derived
//   from this software without specific prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// $
//###########################################################################

//
// Included Files
//
#include "F28x_Project.h"

//
// Function Prototypes
//
void ConfigureADC(void);
void ConfigureEPWM(void);
void SetupADCEpwm(Uint16 channel);
interrupt void adca1_isr(void);

//
// Defines
//
#define RESULTS_BUFFER_SIZE 256

//
// Globals
//
Uint16 AdcaResults[RESULTS_BUFFER_SIZE];
Uint16 resultsIndex;
volatile Uint16 bufferFull;

void main(void)
{
//
// Step 1. Initialize System Control:
// PLL, WatchDog, enable Peripheral Clocks
// This example function is found in the F2837xD_SysCtrl.c file.
//
    InitSysCtrl();

//
// Step 2. Initialize GPIO:
// This example function is found in the F2837xD_Gpio.c file and
// illustrates how to set the GPIO to it's default state.
//
    InitGpio(); // Skipped for this example

//
// Step 3. Clear all interrupts and initialize PIE vector table:
// Disable CPU interrupts
//
    DINT;

//
// Initialize the PIE control registers to their default state.
// The default state is all PIE interrupts disabled and flags
// are cleared.
// This function is found in the F2837xD_PieCtrl.c file.
//
    InitPieCtrl();

//
// Disable CPU interrupts and clear all CPU interrupt flags:
//
    IER = 0x0000;
    IFR = 0x0000;

//
// Initialize the PIE vector table with pointers to the shell Interrupt
// Service Routines (ISR).
// This will populate the entire table, even if the interrupt
// is not used in this example.  This is useful for debug purposes.
// The shell ISR routines are found in F2837xD_DefaultIsr.c.
// This function is found in F2837xD_PieVect.c.
//
    InitPieVectTable();

//
// Map ISR functions
//
    EALLOW;
    PieVectTable.ADCA1_INT = &adca1_isr; //function for ADCA interrupt 1
    EDIS;

//
// Configure the ADC and power it up
//
    ConfigureADC();

//
// Configure the ePWM
//
    ConfigureEPWM();

//
// Setup the ADC for ePWM triggered conversions on channel 0
//
    SetupADCEpwm(0);

//
// Enable global Interrupts and higher priority real-time debug events:
//
    IER |= M_INT1; //Enable group 1 interrupts
    EINT;  // Enable Global interrupt INTM
    ERTM;  // Enable Global realtime interrupt DBGM

//
// Initialize results buffer
//
    for(resultsIndex = 0; resultsIndex < RESULTS_BUFFER_SIZE; resultsIndex++)
    {
        AdcaResults[resultsIndex] = 0;
    }
    resultsIndex = 0;
    bufferFull = 0;

//
// enable PIE interrupt
//
    PieCtrlRegs.PIEIER1.bit.INTx1 = 1;

//
// sync ePWM
//
    EALLOW;
    CpuSysRegs.PCLKCR0.bit.TBCLKSYNC = 1;

//
//take conversions indefinitely in loop
//
    do
    {
        //
        //start ePWM
        //
        EPwm1Regs.ETSEL.bit.SOCAEN = 1;  //enable SOCA
        EPwm1Regs.TBCTL.bit.CTRMODE = 0; //unfreeze, and enter up count mode

        //
        //wait while ePWM causes ADC conversions, which then cause interrupts,
        //which fill the results buffer, eventually setting the bufferFull
        //flag
        //
        while(!bufferFull);
        bufferFull = 0; //clear the buffer full flag

        //
        //stop ePWM
        //
        EPwm1Regs.ETSEL.bit.SOCAEN = 0;  //disable SOCA
        EPwm1Regs.TBCTL.bit.CTRMODE = 3; //freeze counter

        //
        //at this point, AdcaResults[] contains a sequence of conversions
        //from the selected channel
        //

        //
        //software breakpoint, hit run again to get updated conversions
        //
        asm("   ESTOP0");
    }while(1);
}

//
// ConfigureADC - Write ADC configurations and power up the ADC for both
//                ADC A and ADC B
//
void ConfigureADC(void)
{
    EALLOW;

    //
    //write configurations
    //
    AdcaRegs.ADCCTL2.bit.PRESCALE = 6; //set ADCCLK divider to /4
    AdcSetMode(ADC_ADCA, ADC_RESOLUTION_12BIT, ADC_SIGNALMODE_SINGLE);

    //
    //Set pulse positions to late
    //
    AdcaRegs.ADCCTL1.bit.INTPULSEPOS = 1;

    //
    //power up the ADC
    //
    AdcaRegs.ADCCTL1.bit.ADCPWDNZ = 1;

    //
    //delay for 1ms to allow ADC time to power up
    //
    DELAY_US(1000);

    EDIS;
}

//
// ConfigureEPWM - Configure EPWM SOC and compare values
//
void ConfigureEPWM(void)
{
    EALLOW;
    // Assumes ePWM clock is already enabled
    EPwm1Regs.ETSEL.bit.SOCAEN    = 0;    // Disable SOC on A group
    EPwm1Regs.ETSEL.bit.SOCASEL    = 4;   // Select SOC on up-count
    EPwm1Regs.ETPS.bit.SOCAPRD = 1;       // Generate pulse on 1st event
    EPwm1Regs.CMPA.bit.CMPA = 0x0800;     // Set compare A value to 2048 counts
    EPwm1Regs.TBPRD = 0x1000;             // Set period to 4096 counts
    EPwm1Regs.TBCTL.bit.CTRMODE = 3;      // freeze counter
    EDIS;
}

//
// SetupADCEpwm - Setup ADC EPWM acquisition window
//
void SetupADCEpwm(Uint16 channel)
{
    Uint16 acqps;

    //
    // Determine minimum acquisition window (in SYSCLKS) based on resolution
    //
    if(ADC_RESOLUTION_12BIT == AdcaRegs.ADCCTL2.bit.RESOLUTION)
    {
        acqps = 14; //75ns
    }
    else //resolution is 16-bit
    {
        acqps = 63; //320ns
    }

    //
    //Select the channels to convert and end of conversion flag
    //
    EALLOW;
    AdcaRegs.ADCSOC0CTL.bit.CHSEL = channel;  //SOC0 will convert pin A0
    AdcaRegs.ADCSOC0CTL.bit.ACQPS = acqps; //sample window is 100 SYSCLK cycles
    AdcaRegs.ADCSOC0CTL.bit.TRIGSEL = 5; //trigger on ePWM1 SOCA/C
    AdcaRegs.ADCINTSEL1N2.bit.INT1SEL = 0; //end of SOC0 will set INT1 flag
    AdcaRegs.ADCINTSEL1N2.bit.INT1E = 1;   //enable INT1 flag
    AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1; //make sure INT1 flag is cleared
    EDIS;
}

//
// adca1_isr - Read ADC Buffer in ISR
//
interrupt void adca1_isr(void)
{
    AdcaResults[resultsIndex++] = AdcaResultRegs.ADCRESULT0;
    if(RESULTS_BUFFER_SIZE <= resultsIndex)
    {
        resultsIndex = 0;
        bufferFull = 1;
    }

    AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1; //clear INT1 flag

    //
    // Check if overflow has occurred
    //
    if(1 == AdcaRegs.ADCINTOVF.bit.ADCINT1)
    {
        AdcaRegs.ADCINTOVFCLR.bit.ADCINT1 = 1; //clear INT1 overflow flag
        AdcaRegs.ADCINTFLGCLR.bit.ADCINT1 = 1; //clear INT1 flag
    }

    PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
}

//
// End of file
//