使用TMS320F2812的捕获单元测量外部输入方波的频率的代码

下面是使用TMS320F2812的捕获单元测量外部输入方波的频率的代码示例：

#include "DSP281x_Device.h"
#include "DSP281x_Examples.h"

#define EPWM_TIMER_TBPRD  7500  // EPWM 周期

void InitEPwm(void);
void InitECap(void);
interrupt void ecap1_isr(void);

Uint32 cap1 = 0;
Uint32 cap2 = 0;
Uint32 cap3 = 0;
Uint32 freq = 0;

void main(void)
{
    InitSysCtrl();

    DINT;
    InitPieCtrl();

    IER = 0x0000;
    IFR = 0x0000;

    InitPieVectTable();
    EALLOW;
    PieVectTable.ECAP1_INT = &ecap1_isr;
    EDIS;

    InitEPwm();
    InitECap();

    IER |= M_INT3;
    PieCtrlRegs.PIEIER3.bit.INTx1 = 1;

    EINT;
    ERTM;

    while(1)
    {
        freq = 75000000 / (cap2 - cap1);
    }
}

void InitEPwm(void)
{
    EPwm1Regs.TBCTL.bit.CTRMODE = TB_FREEZE;
    EPwm1Regs.TBPRD = EPWM_TIMER_TBPRD;
    EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UP;
}

void InitECap(void)
{
    ECap1Regs.ECEINT.all = 0x0000;
    ECap1Regs.ECCTL1.bit.CAPLDEN = 1;
    ECap1Regs.ECCTL2.bit.TSCTRSTOP = 0;
    ECap1Regs.ECCTL2.bit.CONT_ONESHT = 0;
    ECap1Regs.ECCTL1.bit.CAP1POL = 1;
    ECap1Regs.ECCTL1.bit.CAP2POL = 1;
    ECap1Regs.ECCTL1.bit.CAP3POL = 1;
    ECap1Regs.ECCTL1.bit.CAP4POL = 1;
    ECap1Regs.ECCTL1.bit.CTRRST1 = 1;
    ECap1Regs.ECCTL1.bit.CTRRST2 = 1;
    ECap1Regs.ECCTL1.bit.CTRRST3 = 1;
    ECap1Regs.ECCTL1.bit.CTRRST4 = 1;
    ECap1Regs.ECCTL2.bit.SYNCI_EN = 1;
    ECap1Regs.ECCTL2.bit.SYNCO_SEL = 0;
    ECap1Regs.ECCTL2.bit.SYNCO_EN = 0;
    ECap1Regs.ECCTL2.bit.TSCTRSTOP = 0;
}

interrupt void ecap1_isr(void)
{
    if (ECap1Regs.ECFLG.bit.CEVT1)
    {
        cap1 = ECap1Regs.CAP1;
        ECap1Regs.ECCLR.bit.CEVT1 = 1;
    }

    if (ECap1Regs.ECFLG.bit.CEVT2)
    {
        cap2 = ECap1Regs.CAP2;
        ECap1Regs.ECCLR.bit.CEVT2 = 1;
    }

    if (ECap1Regs.ECFLG.bit.CEVT3)
    {
        cap3 = ECap1Regs.CAP3;
        ECap1Regs.ECCLR.bit.CEVT3 = 1;
    }

    PieCtrlRegs.PIEACK.all = PIEACK_GROUP3;
}

在这个代码示例中，我们使用TMS320F2812的EPwm1模块来生成一个周期为7500的方波，使用ECap1模块来测量外部输入方波的频率。在初始化ECap1模块时，我们将ECap1Regs.ECEINT.all设置为0，即不开启任何中断；将ECap1Regs.ECCTL1和ECap1Regs.ECCTL2中的寄存器位设置为相应的值以便正确地测量输入方波的频率。在捕获到每个上升沿时，我们通过判断ECap1Regs.ECFLG.bit.CEVT1、ECap1Regs.ECFLG.bit.CEVT2和ECap1Regs.ECFLG.bit.CEVT3是否被置位来分别获取每个上升沿的计数值，然后将相应的寄存器位清零，以便下一次捕获。最后，在ecap1_isr中使用PieCtrlRegs.PIEACK.all = PIEACK_GROUP3来清除中断标志。在while循环中，我们计算输入方波的频率，并将结果存储在变量freq中。