Problems Setting Prescaler for PWM capture

[mexp2]

We are using a PWM input to capture a external frequency of a tacho.

With the standard settings everything works fine but when i apply a prescaler during initialization

pwmConfig.prescale = kPWM_Prescale_Divide_64;

or by setting it via

void PWM_SetClockMode

the values of CVAL2 and CVAL3 are always 0x00 and the counter is not counting

My signal has a frequency of 200Hz 

[mexp2]

We use the imxRT1062 with the SDK v 2.13.0

/* Read the PWM default configuration */
PWM_GetDefaultConfig(&pwmConfig);

pwmConfig.reloadLogic 	  = kPWM_ReloadImmediate;
pwmConfig.pairOperation   = kPWM_Independent;
pwmConfig.enableDebugMode = true;

/* Init the pwm */
if( PWM_Init(TACHOPUMP_PERIPHERAL, TACHOPUMP_CHANNEL, &pwmConfig) == kStatus_Fail)
{
	PRINTF("Can't initialize PWM\n");
return;
}

/* Configure the capture input of the PWM for one shot polling */
pwm_input_capture_param_t captureConfig;

captureConfig.captureInputSel = false;
captureConfig.edge0 = kPWM_RisingEdge;
captureConfig.edge1 = kPWM_RisingEdge;
captureConfig.enableOneShotCapture = true;

PWM_SetupInputCapture(TACHOPUMP_PERIPHERAL, TACHOPUMP_CHANNEL, TACHOPUMP_SIGNAL, &captureConfig);

PWM_SetPwmLdok(TACHOPUMP_PERIPHERAL, timerBitmask, true);

PWM_StartTimer(TACHOPUMP_PERIPHERAL, timerBitmask);

with this code everything works as expected, but if i add a prescaler in the configuration

pwmConfig.prescale = kPWM_Prescale_Divide_128;

the counter is not counting anymore

[RaRo]

Hello @mexp2,

First of all, we apologize for the delay to answer you.

Just for double check, could you please tell us where are you placing the kPWM_Prescale_Divide_128? It might be good if you could write the pwmConfig.prescale=kPWM_Prescale_Divide_128; after pwmConfig.pairOperation=kPWM_Independent; and before PWM_Init(). Also, which clock source are you using?

Finally, could you please try to use other values of the prescaler below 64?

Best regards, Raul.

[coderick]

你好，我也遇到了楼主同样的问题，将分频代码去掉或者设为1分频时，Counter可以正常运行，但是设置2分频或更高的分频时Counter就停止了，这是什么原因？

void Capture_config(void)
{
    pwm_input_capture_param_t pwm_input_capture;
    gpio_pin_config_t PWM_pin_config;
  
    //初始化输入捕获管脚
    IOMUXC_SetPinMux(PWM2_PWMA03_IOMUXC, 0U);                             //设置外部引脚的复用功能                              
    IOMUXC_SetPinConfig(PWM2_PWMA03_IOMUXC, PWMC_INPUT_PAD_CONFIG_DATA);     //设置引脚的 pad 属性 

    PWM_pin_config.direction = kGPIO_DigitalInput;
    PWM_pin_config.interruptMode = kGPIO_NoIntmode;

    GPIO_PinInit(PWM2_PWMA03_GPIO, PWM2_PWMA03_GPIO_PIN, &PWM_pin_config);

    //初始化输入捕获配置参数
    pwm_input_capture.captureInputSel = false;
    pwm_input_capture.edge0 = kPWM_RisingEdge;
    //pwm_input_capture.edge1 = kPWM_FallingEdge;
    pwm_input_capture.enableOneShotCapture = false;
    //pwm_input_capture.edgeCompareValue = 10;  //当captureInputSel为FALSE时，此处设值无意义
    pwm_input_capture.fifoWatermark = 0;
    PWM_SetupInputCapture(PI_PWM_BASEADDR, kPWM_Module_3, kPWM_PwmA, &pwm_input_capture);

    //开启捕获中断
    //set_IRQn_Priority(PWM2_3_IRQn,Group4_PreemptPriority_0, Group4_SubPriority_0);//设置中断优先级
    //PWM_EnableInterrupts(PI_PWM_BASEADDR, kPWM_Module_3, kPWM_CaptureA0InterruptEnable| kPWM_CaptureA1InterruptEnable );
    PWM_EnableInterrupts(PI_PWM_BASEADDR, kPWM_Module_3, kPWM_CaptureA0InterruptEnable );
    EnableIRQ(PWM2_3_IRQn);  
}

 /**
* @brief  初始化 PWM  配置参数 
* @retval 无
*/
void PWM_config(void)
{
    pwm_config_t pwmConfig;//定义pwm 配置结构体

    PWM_Deinit(PI_PWM_BASEADDR, kPWM_Module_3);
    /*设置AHB总线时钟和IP总线时钟*/
    CLOCK_SetDiv(kCLOCK_IpgDiv, 0x3); /* Set IPG PODF to 3, divede by 4 */

    /*设置pwm 错误输入为高电平，表示没有错误，只有当pwm 没有错误输入或者禁止错误检测才能正常输出pwm波*/
    XBARA_Init(XBARA1);
    XBARA_SetSignalsConnection(XBARA1, kXBARA1_InputLogicHigh, kXBARA1_OutputFlexpwm1Fault0);
    XBARA_SetSignalsConnection(XBARA1, kXBARA1_InputLogicHigh, kXBARA1_OutputFlexpwm1Fault1);
    XBARA_SetSignalsConnection(XBARA1, kXBARA1_InputLogicHigh, kXBARA1_OutputFlexpwm1234Fault2);
    XBARA_SetSignalsConnection(XBARA1, kXBARA1_InputLogicHigh, kXBARA1_OutputFlexpwm1234Fault3); 
    
    PWM_GetDefaultConfig(&pwmConfig);
    pwmConfig.reloadLogic = kPWM_ReloadPwmFullCycle; //新值在上一个pwm周期输出结束之后加载到缓冲寄存器中
    pwmConfig.pairOperation = kPWM_Independent;      // 工作在独立模式
    pwmConfig.clockSource = kPWM_BusClock;
    pwmConfig.enableDebugMode = true;                // 使能DebugMode 
    pwmConfig.prescale = kPWM_Prescale_Divide_128;    //1320000000/128/65535=16Hz=PWM最小频率

    //初始化 PWM 并且判断初始化是否成功
    if (PWM_Init(PI_PWM_BASEADDR, kPWM_Module_3, &pwmConfig) == kStatus_Fail)
    {
        PRINTF("PWM initialization failed\n");
    }
    Capture_config();
    PWM_SetPwmLdok(PI_PWM_BASEADDR,kPWM_Control_Module_3 , true);   
    PWM_StartTimer(PI_PWM_BASEADDR, kPWM_Control_Module_3 );
}

[Sanket_Parekh]

Hi @mexp2 ,

I hope you are doing well.

Please specify which i.MX Processor is used to debug further.

Thanks & Regards,
Sanket Parekh