[参考译文] TMS320F280025C：EPWM：占空比不变

https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1315480/tms320f280025c-epwm-duty-cycle-not-change

您好！

 我需要生成频率固定为20kHz 且占空比变化的 PWM。 示波器显示20kHz 的脉冲。 不过、我在示波器上始终观察到50%的占空比。 虽然我打算将占空比设置为70%、但示波器始终显示50%的占空比。

对于70%占空比、我已经在代码中初始化以下值：-
#define EPWM2_TIMER_TBPRD 312 //周期寄存器
#define EPWM2_MAX_CMPA 218
#define EPWM2_MIN_CMPA 94

#define EPWM_CMP_UP 1
#define EPWM_CMP_DOWN 0

我为您的参考附上了代码：-

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


// Globals
//
uint16_t sensorSample = 0;
uint16_t isrCount = 0;
int16_t sensorTemp = 0;
float ADC_Voltage=0;
float ADC_Voltage1=0;
float Pressure_kpa=0;
float Pressure_mbar=0;


typedef struct
{
    volatile struct EPWM_REGS *EPwmRegHandle;
    Uint16 EPwm_CMPA_Direction;
    Uint16 EPwmTimerIntCount;
    Uint16 EPwmMaxCMPA;
    Uint16 EPwmMinCMPA;
}EPWM_INFO;

EPWM_INFO epwm2_info;

//
// Function Prototypes
//
void InitEPwm2Example(void);

//
// Main
//
void main(void)
{
    //
    // Initialize device clock and peripherals
    //
    InitSysCtrl();

    //
    // Initialize GPIO
    //
    InitGpio();

    //
    // enable PWM2 to drive motor..
    //'

    CpuSysRegs.PCLKCR2.bit.EPWM2=1;

    //
    // For this case just init GPIO pins for ePWM1, ePWM2, ePWM3
    // These functions are in the F2837xD_EPwm.c file
    //

    InitEPwm2Gpio();

    //
    // 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.
    //
    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).
    //
    InitPieVectTable();

    //
    // For this example, only initialize the ePWM
    ///******************************/
    // for now GPIO-3 is used for PWM signal..20khz PWM signal is generated.
    EALLOW;
    CpuSysRegs.PCLKCR0.bit.TBCLKSYNC = 0;
    EDIS;

    InitEPwm2Example();

    EALLOW;
    CpuSysRegs.PCLKCR0.bit.TBCLKSYNC = 1;
    EDIS;


    EINT;           // Enable Global interrupt INTM
    ERTM;           // Enable Global realtime interrupt DBGM

 
    while(1)
    {
    }
}

void InitEPwm2Example()
{
    //
    // Setup TBCLK
    //
    EPwm2Regs.TBPRD = EPWM2_TIMER_TBPRD;         // Set timer period 801 TBCLKs
    EPwm2Regs.TBPHS.bit.TBPHS = 0x0000;          // Phase is 0
    EPwm2Regs.TBCTR = 0x0000;                    // Clear counter

    //
    // Set Compare values
    //
    EPwm2Regs.CMPA.bit.CMPA = EPWM2_MIN_CMPA;    // Set compare A value

    //
    // Setup counter mode
    //
    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_DIV2;       // Clock ratio to SYSCLKOUT
    EPwm2Regs.TBCTL.bit.CLKDIV = TB_DIV2;

    //
    // Setup shadowing
    //
    EPwm2Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW;
    EPwm2Regs.CMPCTL.bit.SHDWBMODE = CC_SHADOW;
    EPwm2Regs.CMPCTL.bit.LOADAMODE = CC_CTR_ZERO; // Load on Zero
    EPwm2Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO;

    //
    // Set actions
    //
    EPwm2Regs.AQCTLA.bit.CAU = AQ_SET;         // Set PWM2A on event A, up
                                               // count
    EPwm2Regs.AQCTLA.bit.CBD = AQ_CLEAR;       // Clear PWM2A on event B, down
                                               // count

    EPwm2Regs.AQCTLB.bit.ZRO = AQ_CLEAR;       // Clear PWM2B on zero
    EPwm2Regs.AQCTLB.bit.PRD = AQ_SET;         // Set PWM2B on period

    //
    // Interrupt where we will change the Compare Values
    //
    EPwm2Regs.ETSEL.bit.INTSEL = ET_CTR_ZERO;    // Select INT on Zero event
    EPwm2Regs.ETSEL.bit.INTEN = 1;               // Enable INT
    EPwm2Regs.ETPS.bit.INTPRD = ET_3RD;          // Generate INT on 3rd event

    //
    // Information this example uses to keep track
    // of the direction the CMPA/CMPB values are
    // moving, the min and max allowed values and
    // a pointer to the correct ePWM registers
    //
    epwm2_info.EPwm_CMPA_Direction = EPWM_CMP_UP;  // Start by increasing CMPA
    epwm2_info.EPwmTimerIntCount = 0;              // Zero the interrupt counter
    epwm2_info.EPwmRegHandle = &EPwm2Regs;         // Set the pointer to the
                                                   // ePWM module
    epwm2_info.EPwmMaxCMPA = EPWM2_MAX_CMPA;       // Setup min/max CMPA/CMPB
                                                   // values
    epwm2_info.EPwmMinCMPA = EPWM2_MIN_CMPA;

}