【FRDM-MCXN947测评】相移PWM输出测试

bigbat

【FRDM-MCXN947测评】相移PWM输出测试 [复制链接]

本帖最后由 bigbat 于 2025-1-24 16:02 编辑

1、测试介绍

MCXN947系列MCU的FlexPWM 模块，可以通过独立的时钟控制两个通道输出：具有可控制相位输出的PWM波形。每个通道A相或B相可以独立的任意调节PWM相位。该功能可以实现：

中心对齐PWM：

边缘对齐PWM：

相移PWM：

双开关 PWM：

其中的相移输出是我工作中需要的输出，旧有的设计需要多个计数器相互配合实现复杂，而且输出精度和实时性较差，不能实现较为精准的输出和控制。我的要求是：两个通道，A先开启进行预充电，然后在开启输出功率管工作。原有的设计经常出现中断的现象。就是由于相位控制不精确造成的。所以该功能正是我需要的。本次测试也是对该功能进行测试。

硬件：

FRDM-MCXN947开发板一块

双通道100M示波器一台

USB TYPE-C电缆

软件：

GCC ARM Embedded 13.2.1编译器。

测试实现的效果如：

PWM_A相：输出

PWM_B相：输出

2、设置及程序分析

该测试程序参考MCXN947的SDK PWM程序。

NXP的配置工具MCUXpresso Config Tools v16.1除了可以配置芯片引脚路由外，其它的我到现在都没有发现其它的更详细的配置项目。

第一段：

程序的思路是通过MCU PWM的两个寄存器来控制PWM的脉宽位置。参考下面的初始化代码。

/*******************************************************************************
 * Code
 ******************************************************************************/
static void PWM_DRV_Init3PhPwm(void)
{
    uint16_t deadTimeVal;
    pwm_signal_param_t pwmSignal[2];
    uint32_t pwmSourceClockInHz;
    uint32_t pwmFrequencyInHz = APP_DEFAULT_PWM_FREQUENCY;

    pwmSourceClockInHz = PWM_SRC_CLK_FREQ;

    /* Set deadtime count, we set this to about 650ns */
    deadTimeVal = ((uint64_t)pwmSourceClockInHz * 650) / 1000000000;

    pwmSignal[0].pwmChannel       = kPWM_PwmA;
    pwmSignal[0].level            = kPWM_HighTrue;
    pwmSignal[0].dutyCyclePercent = 50; /* 1 percent dutycycle */
    pwmSignal[0].deadtimeValue    = deadTimeVal;
    pwmSignal[0].faultState       = kPWM_PwmFaultState0;
    pwmSignal[0].pwmchannelenable = true;

    pwmSignal[1].pwmChannel = kPWM_PwmB;
    pwmSignal[1].level      = kPWM_HighTrue;
    /* Dutycycle field of PWM B does not matter as we are running in PWM A complementary mode */
    pwmSignal[1].dutyCyclePercent = 50;
    pwmSignal[1].deadtimeValue    = deadTimeVal;
    pwmSignal[1].faultState       = kPWM_PwmFaultState0;
    pwmSignal[1].pwmchannelenable = true;

    /*********** PWMA_SM0 - phase A, configuration, setup 2 channel as an example ************/
    PWM_SetupPwm(BOARD_PWM_BASEADDR, kPWM_Module_0, pwmSignal, 2, kPWM_SignedCenterAligned, pwmFrequencyInHz,
                 pwmSourceClockInHz);

    /*********** PWMA_SM1 - phase B configuration, setup PWM A channel only ************/
#ifdef DEMO_PWM_CLOCK_DEVIDER
    PWM_SetupPwm(BOARD_PWM_BASEADDR, kPWM_Module_1, pwmSignal, 1, kPWM_SignedCenterAligned, pwmFrequencyInHz,
                 pwmSourceClockInHz / (1 << DEMO_PWM_CLOCK_DEVIDER));
#else
    PWM_SetupPwm(BOARD_PWM_BASEADDR, kPWM_Module_1, pwmSignal, 1, kPWM_SignedCenterAligned, pwmFrequencyInHz,
                 pwmSourceClockInHz);
#endif

    /*********** PWMA_SM2 - phase C configuration, setup PWM A channel only ************/
#ifdef DEMO_PWM_CLOCK_DEVIDER
    PWM_SetupPwm(BOARD_PWM_BASEADDR, kPWM_Module_2, pwmSignal, 1, kPWM_SignedCenterAligned, pwmFrequencyInHz,
                 pwmSourceClockInHz / (1 << DEMO_PWM_CLOCK_DEVIDER));
#else
    PWM_SetupPwm(BOARD_PWM_BASEADDR, kPWM_Module_2, pwmSignal, 1, kPWM_SignedCenterAligned, pwmFrequencyInHz,
                 pwmSourceClockInHz);
#endif
}

整个参数配置为

一个结构体 pwm_signal_param_t pwmSignal[2];

一个配置函数PWM_SetupPwm();

函数设计有点过于抽象，函数的设计思路是按照工程化的思维模式设计的，例如：占空比（pwmSignal[0].dutyCyclePercent = 50;）、相位角（pwmSignal[0].deadtimeValue = deadTimeVal;）等概念来输入。对于我这种嵌入式程序思维的人来说，总是觉得不够直接（好像没有掌控感，呵呵！好像NXP不能够让我装了，有点不爽呃）

第二段：

这个思路主要是控制PWM的输出。参考下面代码

/*!
 * [url=home.php?mod=space&uid=159083]@brief[/url] Main function
 */
int main(void)
{
    /* Structure of initialize PWM */
    pwm_config_t pwmConfig;
    pwm_fault_param_t faultConfig;
    uint32_t pwmVal = 4;

    /* Board pin, clock, debug console init */
    /* attach FRO 12M to FLEXCOMM4 (debug console) */
    CLOCK_SetClkDiv(kCLOCK_DivFlexcom4Clk, 1u);
    CLOCK_AttachClk(BOARD_DEBUG_UART_CLK_ATTACH);

    BOARD_InitPins();
    BOARD_InitBootClocks();
    BOARD_InitDebugConsole();

    /* Enable PWM1 SUB Clockn */
    SYSCON->PWM1SUBCTL |=
        (SYSCON_PWM1SUBCTL_CLK0_EN_MASK | SYSCON_PWM1SUBCTL_CLK1_EN_MASK | SYSCON_PWM1SUBCTL_CLK2_EN_MASK);

    PRINTF("FlexPWM driver example\n");

    /*
     * pwmConfig.enableDebugMode = false;
     * pwmConfig.enableWait = false;
     * pwmConfig.reloadSelect = kPWM_LocalReload;
     * pwmConfig.clockSource = kPWM_BusClock;
     * pwmConfig.prescale = kPWM_Prescale_Divide_1;
     * pwmConfig.initializationControl = kPWM_Initialize_LocalSync;
     * pwmConfig.forceTrigger = kPWM_Force_Local;
     * pwmConfig.reloadFrequency = kPWM_LoadEveryOportunity;
     * pwmConfig.reloadLogic = kPWM_ReloadImmediate;
     * pwmConfig.pairOperation = kPWM_Independent;
     */
    PWM_GetDefaultConfig(&pwmConfig);

#ifdef DEMO_PWM_CLOCK_DEVIDER
    pwmConfig.prescale = DEMO_PWM_CLOCK_DEVIDER;
#endif

    /* Use full cycle reload */
    pwmConfig.reloadLogic = kPWM_ReloadPwmFullCycle;
    /* PWM A & PWM B form a complementary PWM pair */
    pwmConfig.pairOperation   = kPWM_ComplementaryPwmA;
    pwmConfig.enableDebugMode = true;

    /* Initialize submodule 0 */
    if (PWM_Init(BOARD_PWM_BASEADDR, kPWM_Module_0, &pwmConfig) == kStatus_Fail)
    {
        PRINTF("PWM initialization failed\n");
        return 1;
    }

    /* Initialize submodule 1, make it use same counter clock as submodule 0. */
    pwmConfig.clockSource           = kPWM_Submodule0Clock;
    pwmConfig.prescale              = kPWM_Prescale_Divide_1;
    pwmConfig.initializationControl = kPWM_Initialize_MasterSync;
    if (PWM_Init(BOARD_PWM_BASEADDR, kPWM_Module_1, &pwmConfig) == kStatus_Fail)
    {
        PRINTF("PWM initialization failed\n");
        return 1;
    }

    /* Initialize submodule 2 the same way as submodule 1 */
    if (PWM_Init(BOARD_PWM_BASEADDR, kPWM_Module_2, &pwmConfig) == kStatus_Fail)
    {
        PRINTF("PWM initialization failed\n");
        return 1;
    }

    /*
     *   config->faultClearingMode = kPWM_Automatic;
     *   config->faultLevel = false;
     *   config->enableCombinationalPath = true;
     *   config->recoverMode = kPWM_NoRecovery;
     */
    PWM_FaultDefaultConfig(&faultConfig);

#ifdef DEMO_PWM_FAULT_LEVEL
    faultConfig.faultLevel = DEMO_PWM_FAULT_LEVEL;
#endif

    /* Sets up the PWM fault protection */
    PWM_SetupFaults(BOARD_PWM_BASEADDR, kPWM_Fault_0, &faultConfig);
    PWM_SetupFaults(BOARD_PWM_BASEADDR, kPWM_Fault_1, &faultConfig);
    PWM_SetupFaults(BOARD_PWM_BASEADDR, kPWM_Fault_2, &faultConfig);
    PWM_SetupFaults(BOARD_PWM_BASEADDR, kPWM_Fault_3, &faultConfig);

    /* Set PWM fault disable mapping for submodule 0/1/2 */
    PWM_SetupFaultDisableMap(BOARD_PWM_BASEADDR, kPWM_Module_0, kPWM_PwmA, kPWM_faultchannel_0,
                             kPWM_FaultDisable_0 | kPWM_FaultDisable_1 | kPWM_FaultDisable_2 | kPWM_FaultDisable_3);
    PWM_SetupFaultDisableMap(BOARD_PWM_BASEADDR, kPWM_Module_1, kPWM_PwmA, kPWM_faultchannel_0,
                             kPWM_FaultDisable_0 | kPWM_FaultDisable_1 | kPWM_FaultDisable_2 | kPWM_FaultDisable_3);
    PWM_SetupFaultDisableMap(BOARD_PWM_BASEADDR, kPWM_Module_2, kPWM_PwmA, kPWM_faultchannel_0,
                             kPWM_FaultDisable_0 | kPWM_FaultDisable_1 | kPWM_FaultDisable_2 | kPWM_FaultDisable_3);

    /* Call the init function with demo configuration */
    PWM_DRV_Init3PhPwm();

    /* Set the load okay bit for all submodules to load registers from their buffer */
    PWM_SetPwmLdok(BOARD_PWM_BASEADDR, kPWM_Control_Module_0 | kPWM_Control_Module_1 | kPWM_Control_Module_2, true);

    /* Start the PWM generation from Submodules 0, 1 and 2 */
    PWM_StartTimer(BOARD_PWM_BASEADDR, kPWM_Control_Module_0 | kPWM_Control_Module_1 | kPWM_Control_Module_2);

    while (1U)
    {
        /* Delay at least 100 PWM periods. */
        SDK_DelayAtLeastUs((1000000U / APP_DEFAULT_PWM_FREQUENCY) * 100, SDK_DEVICE_MAXIMUM_CPU_CLOCK_FREQUENCY);

        pwmVal = pwmVal + 4;

        /* Reset the duty cycle percentage */
        if (pwmVal > 100)
        {
            pwmVal = 4;
        }

        /* Update duty cycles for all 3 PWM signals */
        PWM_UpdatePwmDutycycle(BOARD_PWM_BASEADDR, kPWM_Module_0, kPWM_PwmA, kPWM_SignedCenterAligned, pwmVal);
        PWM_UpdatePwmDutycycle(BOARD_PWM_BASEADDR, kPWM_Module_1, kPWM_PwmA, kPWM_SignedCenterAligned, (pwmVal >> 1));
        PWM_UpdatePwmDutycycle(BOARD_PWM_BASEADDR, kPWM_Module_2, kPWM_PwmA, kPWM_SignedCenterAligned, (pwmVal >> 2));

        /* Set the load okay bit for all submodules to load registers from their buffer */
        PWM_SetPwmLdok(BOARD_PWM_BASEADDR, kPWM_Control_Module_0 | kPWM_Control_Module_1 | kPWM_Control_Module_2, true);
    }

主要代码是：

（1）初始化模块（submodule 0/1/2）

 /* Set PWM fault disable mapping for submodule 0/1/2 */
    PWM_SetupFaultDisableMap(BOARD_PWM_BASEADDR, kPWM_Module_0, kPWM_PwmA, kPWM_faultchannel_0,
                             kPWM_FaultDisable_0 | kPWM_FaultDisable_1 | kPWM_FaultDisable_2 | kPWM_FaultDisable_3);
    PWM_SetupFaultDisableMap(BOARD_PWM_BASEADDR, kPWM_Module_1, kPWM_PwmA, kPWM_faultchannel_0,
                             kPWM_FaultDisable_0 | kPWM_FaultDisable_1 | kPWM_FaultDisable_2 | kPWM_FaultDisable_3);
    PWM_SetupFaultDisableMap(BOARD_PWM_BASEADDR, kPWM_Module_2, kPWM_PwmA, kPWM_faultchannel_0,
                             kPWM_FaultDisable_0 | kPWM_FaultDisable_1 | kPWM_FaultDisable_2 | kPWM_FaultDisable_3);

（2）开始定时器

PWM_StartTimer(BOARD_PWM_BASEADDR, kPWM_Control_Module_0 | kPWM_Control_Module_1 | kPWM_Control_Module_2);

(3)程序循环中控制PWM脉冲的量值

 /* Update duty cycles for all 3 PWM signals */
        PWM_UpdatePwmDutycycle(BOARD_PWM_BASEADDR, kPWM_Module_0, kPWM_PwmA, kPWM_SignedCenterAligned, pwmVal);
        PWM_UpdatePwmDutycycle(BOARD_PWM_BASEADDR, kPWM_Module_1, kPWM_PwmA, kPWM_SignedCenterAligned, (pwmVal >> 1));
        PWM_UpdatePwmDutycycle(BOARD_PWM_BASEADDR, kPWM_Module_2, kPWM_PwmA, kPWM_SignedCenterAligned, (pwmVal >> 2));

3、测试过程

(1) 将A0相输出和A1输出连接到示波器上去。

(2)将USB Type-C电缆连接到PC主机

(3)运行程序

调节示波器，可以查看输出波形。

波形输出为设计的方式，但是波形出现了很多的“过冲”现象，不知道是什么原因造成的。

4、总结

通过测试可以更加深入的了解NXP FlexPWM的控制原理，NXP使用较为工程化的函数封装来简化编程的复杂度。我个人觉得如果想很好的了解FlexPWM的模块工作原理还是需要了解各种寄存器和模块的设计原理。

freebsder

波形还是挺好的

【FRDM-MCXN947测评】相移PWM输出测试 [复制链接]

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