MSP432E401Y: PWM外设的频率问题

你好 这是driverlib的例程 然而在TI drivers在PWM_open()内使用不同的频率或周期可能会出现问题。

林畅 说：

可能会出现问题

请问能否说一下具体是什么问题？是会在编译时报错还是可以编译成功但使用时功能不正常？

若是可以，能否给出完整代码，我在开发板上测试一下

可以过编译。然而PWM_open()的返回值是NULL.具体情况是在PWMMSP432E4.c里initHw()中此处返回的错误导致。我这里尽管使用了不同generator的引脚，可是只要频率不同就无法打开PWM。我该如何向你发送代码？

林畅 说：

我该如何向你发送代码？

您应该会收到我发给您的消息吧，直接回复即可。使用附件压缩包的方式上传，谢谢

抱歉，我这边找了一下，没有MSP432E的板子，所以我是使用MSP432P系列来测试的

代码如下，不建议您在循环内打开PWM，即

/*** - custom variables end - ***/
for(int i=0;i<CONFIG_PWM_COUNT;i++){
pwmHandle[i] = PWM_open(i, pwmParams+i);
if(pwmHandle[i]==NULL){
//error: PWM did not open
//there had better a UART output
while(1);
}

而是尝试逐个打开

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/*
 *  ======== pwmled2.c ========
 */
/* For usleep() */
#include <unistd.h>
#include <stddef.h>

/* Driver Header files */
#include <ti/drivers/PWM.h>

/* Driver configuration */
#include "ti_drivers_config.h"

/*
 *  ======== mainThread ========
 *  Task periodically increments the PWM duty for the on board LED.
 */
void *mainThread(void *arg0)
{
    /* Period and duty in microseconds */
    uint16_t   pwmPeriod = 3000;
    uint16_t   duty = 0;
    uint16_t   dutyInc = 100;

    /* Sleep time in microseconds */
    uint32_t   time = 50000;
    PWM_Handle pwm1 = NULL;
    PWM_Handle pwm2 = NULL;
    PWM_Params params;

    /* Call driver init functions. */
    PWM_init();

    PWM_Params_init(&params);
    params.dutyUnits = PWM_DUTY_US;
    params.dutyValue = 0;
    params.periodUnits = PWM_PERIOD_US;
    params.periodValue = pwmPeriod;
    pwm1 = PWM_open(CONFIG_PWM_0, &params);
    if (pwm1 == NULL) {
        /* CONFIG_PWM_0 did not open */
        while (1);
    }

    PWM_start(pwm1);

    pwm2 = PWM_open(CONFIG_PWM_1, &params);
    if (pwm2 == NULL) {
        /* CONFIG_PWM_0 did not open */
        while (1);
    }

    PWM_start(pwm2);

    /* Loop forever incrementing the PWM duty */
    while (1) {
        PWM_setDuty(pwm1, duty);

        PWM_setDuty(pwm2, duty);

        duty = (duty + dutyInc);

        if (duty == pwmPeriod || (!duty)) {
            dutyInc = - dutyInc;
        }

        usleep(time);
    }
}

能讲一下原因吗

您可以看一下下面链接的 

MPS432 PWM Driver Configuration

http://software-dl.ti.com/msp430/msp430_public_sw/mcu/msp430/SIMPLELINK_MSP432_SDK/1.20.00.45/exports/docs/tidrivers/doxygen/html/_p_w_m_timer_m_s_p432_8h.html 

以及说明：

• Only one PWM index can be used at a time; calling PWM_open() a second time with the same index previously passed to PWM_open() will result in an error. You can, though, re-use the index if the instance is closed via PWM_close(). In the example code, Board_PWM0 is passed to PWM_open(). This macro is defined in the example's Board.h file.

另外我之前附上的代码是MSP432P401R系列的例程

你好，我虽然使用了循环打开PWM，但是我并没有使用同样的index，而是利用了循环变量i“PWM_open(i,params+i)”

此外，MSP432P4和E4型号名字相似，但是PWM实现外设不同，差别较大，还麻烦您帮我再问一问，以解我心头之困，谢谢

谢谢您的反馈，我之后会咨询下同事后给您回复