SPWM Problem

Enes,

In your program, how have you declared the variable "a"?

Regards,

Richard

"a" is declareded as a float variable. but I forgot copy of these part of code sory for this mistake.

I think that;
I have 5kHz carrier triangular wave and every zero point, my code goes EPWM interrupt service rutine and calculate new sin wave value and this value assign to epwm compare register. every zero point of pwm counter I need new sin value and my pwm 5kHz, my sin wave is 50Hz so that I need 5kHz/50Hz=100 sample for one period sinwave. Am I right?

Enes,

Yes, that is correct.

I have your code building and running.  So far it is doing what I expect.  What is the distortion you are seeing?

Regards,

Richard

In this code I want to generate SPWM.
I connect a low pass filter (R=1kohm C=100nF)in the pin 80 (epwm2A pin) to see a 50Hz sin wave. but ı do not see sin wave.
pwm signal not satisfy the sin wave. pwm signal not switching and It stays in the same position (0 or 1).

tomorrow, I will share the ossiloscope screen video.

Hi Richard, sory for late replay,
Here my latest code for spwm.this code is modified version "epwm_updown_aq_cpu01.c" project to developted for TMS320F28377S Launchpad examples.
Can you run this code and sy me whre ı mistake.

in this link my oscilloscope screen video;
www.youtube.com/watch

thank you so much for all replays.
// Included Files
//
#include "F28x_Project.h"
#include "math.h"
#define EPWM2_TIMER_TBPRD 5000 // 5kHz PWM Period register
#define PI 3.14159265358979323846
void InitEPwm2Example(void);
__interrupt void epwm2_isr(void);
unsigned int i=0,m=0,k=0;
float a=0;
float b[101]={0};
// Main

void main(void)
{
InitSysCtrl();

/*Here I generate sin look up table for sin values, I have 100 sample for one period 50Hz sin wave.Also I multiple buy -1 of negative values of sin wave.

Sin(w*t)=sin(2*pi*f*t)=sin(2*pi*50*(20ms/100)*sample_number)

Sample number=0,1,2,3,4,……………,100

f=50Hz

m=sample number*/

for(m=0;m<100;m++){
a=sin(PI*0.02*m);
if(a<=0){
a=-a;
}
b[m]=5000*a;
}
b[100]=0;
EALLOW;

GpioCtrlRegs.GPAPUD.bit.GPIO2 = 1; // Disable pull-up on GPIO2 (EPWM2A)
GpioCtrlRegs.GPAMUX1.bit.GPIO2 = 1; // Configure GPIO2 as EPWM2A

EDIS;
DINT;
InitPieCtrl();
IER = 0x0000;
IFR = 0x0000;
InitPieVectTable();
EALLOW;
PieVectTable.EPWM2_INT = &epwm2_isr;
EDIS;
EALLOW;
CpuSysRegs.PCLKCR0.bit.TBCLKSYNC = 0;
EDIS;
InitEPwm2Example();
EALLOW;
CpuSysRegs.PCLKCR0.bit.TBCLKSYNC = 1;
EDIS;
IER |= M_INT3;
PieCtrlRegs.PIEIER3.bit.INTx2 = 1;
CpuSysRegs.PCLKCR2.bit.EPWM2=1;
EINT; // Enable Global interrupt INTM
ERTM; // Enable Global realtime interrupt DBGM

for(;;)
{
asm (" NOP");
}
}

__interrupt void epwm2_isr(void)
{
/*Here my code assign a new sin value into compare reg. but negative side of sin wave pwm logic is invertered.*/
a=sin(PI*0.02*i);
if (a>=0){
EPwm2Regs.AQCTLA.bit.CAU = AQ_CLEAR; // Set PWM2A on event A, up
EPwm2Regs.AQCTLA.bit.CAD =AQ_SET; // Clear PWM2A on event B, down
EPwm2Regs.CMPA.bit.CMPA =b[i];
}
else {
EPwm2Regs.AQCTLA.bit.CAU =AQ_SET; // Set PWM2A on event A, up
EPwm2Regs.AQCTLA.bit.CAD = AQ_CLEAR; // Clear PWM2A on event B, down
EPwm2Regs.CMPA.bit.CMPA =b[i];
}
i++;
if (i==101){
i=0;
}
EPwm2Regs.ETCLR.bit.INT = 1;
PieCtrlRegs.PIEACK.all = PIEACK_GROUP3;
}
void InitEPwm2Example()
{
EPwm2Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO; // hem zero hemde TBPRD zamanında intrrupt alıyo.
EPwm2Regs.ETSEL.bit.INTEN = 1; // Enable INT
EPwm2Regs.ETPS.bit.INTPRD = ET_1ST; // Generate INT on 1st event
EPwm2Regs.TBCTL.bit.CTRMODE = TB_COUNT_UPDOWN; // Count up and down
EPwm2Regs.TBCTL.bit.PHSEN = TB_DISABLE; // Disable phase loading
EPwm2Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1; // Clock ratio to SYSCLKOUT
EPwm2Regs.TBCTL.bit.CLKDIV = TB_DIV2;
EPwm2Regs.CMPCTL.bit.SHDWAMODE = CC_IMMEDIATE;
EPwm2Regs.CMPA.bit.CMPA =0;
EPwm2Regs.TBPRD = EPWM2_TIMER_TBPRD; // Set timer period 801 TBCLKs
EPwm2Regs.TBPHS.bit.TBPHS = 0x0000; // Phase is 0
EPwm2Regs.TBCTR = 0x0000; // Clear counter
}

Richard,
Thank you so much for all reply, I understand very well :)

Hi Enes,

G mrng..!

Can u share me the code and guide me with the instructions for F28335.

Actually i copied the above code and getting errors as below while building.,

Hi,

Nayeem Basha Shaik

I have never used the F28355.I using F28377s. The attached documentt can help you. 

In this document, you can see the PWM compare register usued like that;

EPwm1Regs.CMPA.hlaf.CMPA = value  // may be you can use b[i] as value.

EPwm1Regs.CMPB = compare value1

EPwm2Regs.CMPA.hlaf.CMPA = value2

EPwm2Regs.CMPB = compare value3

Enhanced Pulse Width Modulator epwm.pdf

Ya... I got it dude, anyhow thanks alot or your reply....