eCAP

#include "DSP28x_Project.h" // Device Headerfile and Examples Include File
#include "DSP2833x_ECap_defines.h"
#define EPWM1_TIMER_TBPRD 3750 // Period register 系统始终为150MHZ，下面的程序进行了4分频，即为37.5MHZ,这样得到的是10KHZ

Uint32  TS1 = 0;
Uint32  TS2 = 0;
Uint32  TS3 = 0;
Uint32  TS4 = 0;
Uint32 PEROID = 0;
Uint32 DUTY1 = 0;
Uint32 DUTY2 = 0;
Uint32 initcount = 0;
Uint32 duty = 3750 / 2;
__interrupt void ecap1_isr(void);
void PWM1_Init()//初始化PWM
{
    EALLOW;
    SysCtrlRegs.PCLKCR1.bit.ECAP1ENCLK = 1;; // Stop all the TB clocks
    EDIS;
    // Setup TBCLK
    EPwm1Regs.TBPRD = EPWM1_TIMER_TBPRD; // 设置周期
    EPwm1Regs.TBPHS.half.TBPHS = 0x0000; // 如果使能的话，当有同步信号时，会将这个值赋值给CTR
    EPwm1Regs.TBCTR = 0x0000; // 计数器初始值赋值为0

    // Setup counter mode
    EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UPDOWN; //计数模式
    EPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE; // Disable phase loading
    EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV2; // 这里是进行2分频
    EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV2; //这里也是2分频
    EPwm1Regs.TBCTL.bit.SYNCOSEL = TB_CTR_ZERO;

    // Setup shadowing
    EPwm1Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW; //采用影子寄存器跟新
    EPwm1Regs.CMPCTL.bit.SHDWBMODE = CC_SHADOW;
    EPwm1Regs.CMPCTL.bit.LOADAMODE = CC_CTR_ZERO; // Load on Zero
    EPwm1Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO;

    // Set actions
    EPwm1Regs.AQCTLA.bit.CAU = AQ_CLEAR; // Set PWM1A on event A, up count
    EPwm1Regs.AQCTLA.bit.CAD = AQ_SET; // Clear PWM1A on event A, down count

    EPwm1Regs.DBCTL.bit.OUT_MODE = DB_FULL_ENABLE;
    EPwm1Regs.DBCTL.bit.POLSEL = DB_ACTV_HIC;
    EPwm1Regs.DBFED = 50;
    EPwm1Regs.DBRED = 50;

    EPwm1Regs.CMPA.half.CMPA = (EPWM1_TIMER_TBPRD >> 1);

}
void Pwm_Init()
{
    /*首先进行的是PWM1引脚的初始化，因为PWM1的引脚为GPIO0和GPIO1，这两个引脚可以是普通的IO口，也可以复用输出PWM，这里选用复用功能*/
    EALLOW;
    GpioCtrlRegs.GPAPUD.bit.GPIO0 = 0; // Enable pull-up on GPIO0 (EPWM1A)
    GpioCtrlRegs.GPAPUD.bit.GPIO1 = 0; // Enable pull-up on GPIO1 (EPWM1B)
    GpioCtrlRegs.GPAMUX1.bit.GPIO0 = 1; // Configure GPIO0 as EPWM1A复用功能设置，为0代表是普通IO口
    GpioCtrlRegs.GPAMUX1.bit.GPIO1 = 1; // Configure GPIO1 as EPWM1B
    EDIS;

    EALLOW;
    SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 0; // Stop all the TB clocks
    EDIS;

    PWM1_Init();

    EALLOW;
    SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 1; // Start all the timers synced
    EDIS;
}
void InitECapture()
{
   ECap1Regs.ECEINT.all = 0x0000; // Disable all capture interrupts
   ECap1Regs.ECCLR.all = 0xFFFF; // Clear all CAP interrupt flags

   ECap1Regs.ECCTL1.bit.CAPLDEN = 0; // Disable CAP1-CAP4 register loads
   ECap1Regs.ECCTL2.bit.TSCTRSTOP = EC_STOP; // Make sure the counter is stopped

   // Configure peripheral registers
   ECap1Regs.ECCTL2.bit.CONT_ONESHT = EC_CONTINUOUS; // One-shot
   ECap1Regs.ECCTL2.bit.STOP_WRAP = 3; // Stop at 4 events

   ECap1Regs.ECCTL1.bit.CAP1POL = EC_RISING; // Rising edge
   ECap1Regs.ECCTL1.bit.CAP2POL = EC_FALLING; // Rising edge
   ECap1Regs.ECCTL1.bit.CAP3POL = EC_RISING; // Rising edge
   ECap1Regs.ECCTL1.bit.CAP4POL = EC_FALLING; // Rising edge

   ECap1Regs.ECCTL1.bit.CTRRST1 = EC_ABS_MODE; // Difference operation
   ECap1Regs.ECCTL1.bit.CTRRST2 = EC_ABS_MODE; // Difference operation
   ECap1Regs.ECCTL1.bit.CTRRST3 = EC_ABS_MODE; // Difference operation
   ECap1Regs.ECCTL1.bit.CTRRST4 = EC_ABS_MODE; // Difference operation

   ECap1Regs.ECCTL2.bit.SYNCI_EN = EC_DISABLE; // Enable sync in
   ECap1Regs.ECCTL2.bit.SYNCO_SEL = EC_SYNCO_DIS; // Pass through
   ECap1Regs.ECCTL1.bit.CAPLDEN = EC_ENABLE; // Enable capture units

   ECap1Regs.ECCTL1.bit.PRESCALE = EC_DIV1;
   ECap1Regs.ECCTL2.bit.CAP_APWM = EC_CAP_MODE;

   ECap1Regs.ECCTL2.bit.TSCTRSTOP = EC_RUN; // Start Counter
   ECap1Regs.ECEINT.bit.CEVT4 = 1; // 4 events = interrupt
}
void cap_init()
{
    EALLOW;
    GpioCtrlRegs.GPAPUD.bit.GPIO24 = 0; // Enable pull-up on cap1 (EPWM1A)
    GpioCtrlRegs.GPAMUX2.bit.GPIO24 = 1; // Configure GPIO0 as cap1复用功能设置，为0代表是普通IO口
//  GpioCtrlRegs.GPAPUD.bit.GPIO25 = 0; // Enable pull-up on GPIO1 (EPWM1B)
//  GpioCtrlRegs.GPAMUX1.bit.GPIO25 = 1; // Configure GPIO1 as EPWM1B
    EDIS;

    InitECapture();
}
void All_Init()
{
    InitSysCtrl();
    DINT;

    InitPieCtrl();
    IER = 0x0000;
    IFR = 0x0000;
    InitPieVectTable();

    EALLOW;
    PieVectTable.ECAP1_INT = &ecap1_isr;
    EDIS;


    Pwm_Init();
    cap_init();
    IER |= M_INT4;
    PieCtrlRegs.PIEIER4.bit.INTx1 = 1;

    EINT;
    ERTM;
}


void main(void)
{
    All_Init();
    while(1)
    {
        EPwm1Regs.CMPA.half.CMPA = duty;
    }
}
__interrupt void ecap1_isr(void)
{
   TS1 = ECap1Regs.CAP1;
   TS2 = ECap1Regs.CAP2;
   TS3 = ECap1Regs.CAP3;
   TS4 = ECap1Regs.CAP4;

   PEROID = TS3 - TS1;
   DUTY1 = TS2 - TS1;
   DUTY2 = TS3 - TS2;
   initcount++;

   ECap1Regs.ECCLR.bit.CEVT4 = 1;
   ECap1Regs.ECCLR.bit.INT = 1;
   ECap1Regs.ECCTL2.bit.REARM = 1;

   PieCtrlRegs.PIEACK.all = PIEACK_GROUP4;
}

CAP有两个功能，一个是输入捕获，另一个是APWM，即输出PWM波。虽然可以输出PWM，但是我觉得好像没啥用。
在DSP中有一个MOD4寄存器，这个寄存器是不断对数据进行余4，即0-1-2-3-0-1-2-3…….不断的进行循环。比如现在MOD4的值为0，然后基准计数器不断地累加，当捕获到上升沿（或者下降沿，看自己的设定）时，将此时基准计数器的值存入CAP1中，然后MOD4加一，然后当捕获到下一个下降沿时，将此时的基准寄存器的值存入CAP2，然后MOD4加一，依次循环。

最后将period = T3 - T1，duty = T2 - T1