CCS/TMS320F28377D: 28377D:sample rate

//###########################################################################
// FILE:   adc_soc_epwm_cpu01.c
// TITLE:  ADC triggering via epwm for F2837xS.
//
//! \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.
//
//###########################################################################
// $TI Release: F2837xS Support Library v190 $
// $Release Date: Mon Feb  1 16:59:09 CST 2016 $
// $Copyright: Copyright (C) 2014-2016 Texas Instruments Incorporated -
//             http://www.ti.com/ ALL RIGHTS RESERVED $
//###########################################################################

#include "F28x_Project.h"     // Device Headerfile and Examples Include File

void ConfigureADC(void);
void ConfigureEPWM(void);
void SetupADCEpwm(Uint16 channel);
interrupt void adca1_isr(void);

//buffer for storing conversion results
#define RESULTS_BUFFER_SIZE 512
int16 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 F2837xS_SysCtrl.c file.
    InitSysCtrl();

// Step 2. Initialize GPIO:
// This example function is found in the F2837xS_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 F2837xS_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 F2837xS_DefaultIsr.c.
// This function is found in F2837xS_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);
}

//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;
}

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 = 0x4A59;          // Set compare A value to 2048 counts
	EPwm1Regs.TBPRD = 0x94B1;			        // Set period to 4096 counts
	EPwm1Regs.TBCTL.bit.CTRMODE = 3;            // freeze counter
	EDIS;
}

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
}

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
	PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
}