Unable to stop PWM

[JoeTing]

Hi guys,

I am now facing a problem that I can't stop the pwm by using nrf_drv_pwm_stop.

Here's my initial code for pwm and start the pwm in the while loop.

The output pin can complete generate the pulse 400Hz bit lust can't stop.

void PWM_Init(void)
{
    NRF_LOG_INFO("Demo 5");

    nrf_drv_pwm_config_t const motor_configure =
    {
        .output_pins =
        {
            PWM_pin | NRF_DRV_PWM_PIN_INVERTED,      // channel 0
            NRFX_PWM_PIN_NOT_USED,
            NRFX_PWM_PIN_NOT_USED,
            NRFX_PWM_PIN_NOT_USED					
           // BSP_LED_2 | NRF_DRV_PWM_PIN_INVERTED, // channel 1
          //  BSP_LED_3 | NRF_DRV_PWM_PIN_INVERTED, // channel 2
           // BSP_LED_1 | NRF_DRV_PWM_PIN_INVERTED  // channel 3
        },
        .irq_priority = APP_IRQ_PRIORITY_LOWEST,
        .base_clock   = NRF_PWM_CLK_1MHz,
        .count_mode   = NRF_PWM_MODE_UP,
        .top_value    = 2500,
        .load_mode    = NRF_PWM_LOAD_INDIVIDUAL,
        .step_mode    = NRF_PWM_STEP_AUTO
    };
    APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &motor_configure, NULL));
    m_used |= USED_PWM(0);
		printf("PWM Init successful \r\n");

}

void PWM_Start(void){
	    // This array cannot be allocated on stack (hence "static") and it must
    // be in RAM (hence no "const", though its content is not changed).
    static nrf_pwm_values_individual_t /*const*/ seq_values[] =
    {
        { 0x8000},
        {      0}
    };
    nrf_pwm_sequence_t const seq =
    {
        .values.p_individual = seq_values,
        .length              = NRF_PWM_VALUES_LENGTH(seq_values),
        .repeats             = 0,
        .end_delay           = 0
    };

    (void)nrf_drv_pwm_simple_playback(&m_pwm0, &seq, 1, NRF_DRV_PWM_FLAG_LOOP);
}

void PWM_Stop(void){
	uint32_t err_code;
	//if (nrfx_pwm_is_stopped(&m_pwm0) != 1)
	err_code = nrf_drv_pwm_stop(&m_pwm0, true);
	
	if(err_code != NRF_SUCCESS){
		printf("motor stop failed  %d \r\n", err_code);
	}
}

    for (;;)
    {
			PWM_Start();
			nrf_delay_ms(500);
			PWM_Stop();
      idle_state_handle();
    }

The error code after calling nrf_drv_pwm_stop is one.

I can't recognize where the error it is.

[Vidar Berg]

Hello,

Try to add a delay after PWM_Stop():

    for (;;)
    {
		PWM_Start();
		nrf_delay_ms(500);
		PWM_Stop();
		nrf_delay_ms(500);
		
		/* Application level interrupts may prevent this function 
		 * from entering sleep. 
		 */	
        idle_state_handle(); 
    }

I don't see the implementation of idle_state_handle(), but I think what's happening in your program is that PWM_Stop() is immediately being followed by a call to PWM_Start(). nrfx_pwm_stop() is a boolean function and returns '1' when the PWM is stopped, so it's not returning any errors.

Best regards,

Vidar

[JoeTing]

Hi Vidar,

I just tried  nrfx_pwm_stop() but still didn't work.

So I did another method to control the duty cycle.

Here's my code below：

void PWM_Init_Start(void)
{
    NRF_LOG_INFO("Demo 5");

    nrf_drv_pwm_config_t const AFE4404_PWM_Config =
    {
        .output_pins =
        {
            Motor_pin | NRF_DRV_PWM_PIN_INVERTED, // channel 0
           // BSP_LED_2 | NRF_DRV_PWM_PIN_INVERTED, // channel 1
          //  BSP_LED_3 | NRF_DRV_PWM_PIN_INVERTED, // channel 2
           // BSP_LED_1 | NRF_DRV_PWM_PIN_INVERTED  // channel 3
        },
        .irq_priority = APP_IRQ_PRIORITY_LOWEST,
        .base_clock   = NRF_PWM_CLK_1MHz,
        .count_mode   = NRF_PWM_MODE_UP,
        .top_value    = 1,
        .load_mode    = NRF_PWM_LOAD_INDIVIDUAL,
        .step_mode    = NRF_PWM_STEP_AUTO
    };
    APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &AFE4404_PWM_Config, NULL));
    m_used |= USED_PWM(0);


}

void PWM_Start_Cycle(void){
	    // This array cannot be allocated on stack (hence "static") and it must
    // be in RAM (hence no "const", though its content is not changed).
    static nrf_pwm_values_individual_t /*const*/ seq_values[] =
    {
        {      0},
        {      0},
				{      0},
				{      0},
				{      0},
				{      0},
				{      0},
				{      0},
				{      0},
				{ 0x8000}
    };
    nrf_pwm_sequence_t const seq =
    {
        .values.p_individual = seq_values,
        .length              = NRF_PWM_VALUES_LENGTH(seq_values),
        .repeats             = 0,
        .end_delay           = 0
    };

    (void)nrf_drv_pwm_simple_playback(&m_pwm0, &seq, 1, NRF_DRV_PWM_FLAG_LOOP);
}

void PWM_Init_Stop(void)
{
    NRF_LOG_INFO("Demo 5");

    nrf_drv_pwm_config_t const AFE4404_PWM_Config =
    {
        .output_pins =
        {
            Motor_pin | NRF_DRV_PWM_PIN_INVERTED, // channel 0
           // BSP_LED_2 | NRF_DRV_PWM_PIN_INVERTED, // channel 1
          //  BSP_LED_3 | NRF_DRV_PWM_PIN_INVERTED, // channel 2
           // BSP_LED_1 | NRF_DRV_PWM_PIN_INVERTED  // channel 3
        },
        .irq_priority = APP_IRQ_PRIORITY_LOWEST,
        .base_clock   = NRF_PWM_CLK_1MHz,
        .count_mode   = NRF_PWM_MODE_UP,
        .top_value    = 1,
        .load_mode    = NRF_PWM_LOAD_INDIVIDUAL,
        .step_mode    = NRF_PWM_STEP_AUTO
    };
    APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &AFE4404_PWM_Config, NULL));
    m_used |= USED_PWM(0);


}

void PWM_Stop_Cycle(void){
	    // This array cannot be allocated on stack (hence "static") and it must
    // be in RAM (hence no "const", though its content is not changed).
    static nrf_pwm_values_individual_t /*const*/ seq_values[] =
    {
        { 0x8000},
        { 0x8000},
				{ 0x8000},
				{ 0x8000},
				{ 0x8000},
				{ 0x8000},
				{ 0x8000},
				{ 0x8000},
				{ 0x8000},
				{ 0x8000}
    };
    nrf_pwm_sequence_t const seq =
    {
        .values.p_individual = seq_values,
        .length              = NRF_PWM_VALUES_LENGTH(seq_values),
        .repeats             = 0,
        .end_delay           = 0
    };

    (void)nrf_drv_pwm_simple_playback(&m_pwm0, &seq, 1, NRF_DRV_PWM_FLAG_LOOP);
}

void PWM_Start(void){
	PWM_Init_Start();
	PWM_Start_Cycle();
}

void PWM_Stop(void){
	PWM_Init_Stop();
	PWM_Stop_Cycle();
}

And I just combine the function into below:

void mask_on(void){
	PWM_Start();
	nrf_delay_ms(2000);
	PWM_Stop();	
}

But something weird is that when I call the mask_on in my main region, the pwm is on and off repeatedly.

Are there any another way to stop the pwm？

[Vidar Berg]

Hi,

Did you try to add the additional delay (nrf_delay_ms) in your original code like I suggested? I didn't mean to suggest that you should change the PWM_Stop() function.