how to stop pwm and set pin to clear

[wuvo.leo]

Hi,all.i use pwm with sdk8.1 sample (SDK8.1\example\peripheral\pwm),my question is how to stop pwm and set the pin to low level? is my code correct? my pwm init code:

---

static uint32_t init_pwm(uint32_t perior,uint8_t pin)
 {	 
	 	uint32_t err_code = 0; 
    /* 2-channel PWM, 200Hz, output on DK LED pins. */
	  app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(perior, pin);
	 
	 pwm1_cfg.pin_polarity[0] = APP_PWM_POLARITY_ACTIVE_LOW;
    
    /* Initialize and enable PWM. */
    err_code = app_pwm_init(&PWM1,&pwm1_cfg,pwm_ready_callback);
    APP_ERROR_CHECK(err_code);

    return err_code;
}
------------------------------------------------------------------------------

pwm stop code:
void pwm_stop( void )
{
   app_pwm_disable(&PWM1);
}
----------------------------------------------------------------------------

pwm start code:
void pwm_start( void )
{   
   app_pwm_enable(&PWM1);
}

[Susheel Nuguru]

Hi wuvo, I have noticed that app_pwm library does not disable a GPIOTE config, which means that it does not free the pin from gpiote after you are done. I created a ticket for it for the team.

For your code you can do this.

1. before initializing pwm library, you configure the pin through gpio interface

   nrf_gpio_pin_dir_set(pin_number, NRF_GPIO_PIN_DIR_OUTPUT); nrf_gpio_pin_clear(pin_number);

2. Then you initialize PWM using app_pwm library, do your stuff

3. in your pwm_stop add three lines to it

   void pwm_stop( void ) { app_pwm_disable(&PWM1); nrf_drv_gpiote_out_task_disable(pin_number); nrf_gpio_cfg_output(pin_number) nrf_gpio_pin_clear(pin_number); }

Now as soon as the pin is freed by nrf_drv_gpiote_out_task_disable then gpio configuration will take into effect.

EDIT: 10.08.2015

PAN-73 workaround is enabled by default in app_pwm_init

PAN-73 workaround is disabled in app_pwm_uninit

This means there will be increase in power consumption (~50uA) if the PAN-72 workaround is enabled.

Check here

[wuvo.leo]

Thanks! And after stop pwm,how to restart it?

[Susheel Nuguru]

void pwm_start( void ) {
nrf_drv_gpiote_out_task_enable(pin_number); app_pwm_enable(&PWM1); }

[wuvo.leo]

Thanks,Aryan.i tested as what your say,but the pin is high level always.no effects.i want to controll buzzer used pwm.what's wrong?i reconfig pwm before i start(restart) pwm using code as follow:

-------------------------------------------------------------------------
uint32_t reconfig_pwm(uint32_t perior,uint8_t pin)
{
	uint32_t err_code = 0;

	err_code = app_pwm_uninit(&PWM1); 	
	APP_ERROR_CHECK(err_code);

	if( err_code == NRF_SUCCESS)
	{
	  err_code =	init_pwm(perior,pin);
		APP_ERROR_CHECK(err_code);
	}
	
	//while (app_pwm_channel_duty_set(&PWM1, 0, 50) == NRF_ERROR_BUSY);

	return err_code;

}

static uint32_t init_pwm(uint32_t perior,uint8_t pin)
 {	 
	 	uint32_t err_code = 0;

		nrf_gpio_pin_dir_set(pin, NRF_GPIO_PIN_DIR_OUTPUT);
		nrf_gpio_pin_clear(pin);
	 
    /* 2-channel PWM, 200Hz, output on DK LED pins. */
	  app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(perior, pin);
	 
	 pwm1_cfg.pin_polarity[0] = APP_PWM_POLARITY_ACTIVE_LOW;
    
    /* Initialize and enable PWM. */
    err_code = app_pwm_init(&PWM1,&pwm1_cfg,pwm_ready_callback);
    APP_ERROR_CHECK(err_code);

    return err_code;
}
------------------------------------------------------------------------------------------------
then,start it:
void pwm_start( void )
{   
   app_pwm_enable(&PWM1);
	 while (app_pwm_channel_duty_set(&PWM1, 0, 50) == NRF_ERROR_BUSY);
}
-----------------------------------------------------------------------------------------------
stop as this:
void pwm_stop( void )
{ 
	  app_pwm_disable(&PWM1);
	  nrf_drv_gpiote_out_task_disable(SPEAKER_PIN);
          nrf_gpio_pin_clear(SPEAKER_PIN);

//	  while (app_pwm_channel_duty_set(&PWM1, 0, 0) == NRF_ERROR_BUSY);
	  pos = 0;
	  time = 0;
	  k = 0;
	  freq = 0;
}

[Susheel Nuguru]

That should have worked, If this does not work then it means that somewhere GPIOTE still owns the pin.

nrf_drv_gpiote_out_task_disable(SPEAKER_PIN);
nrf_gpio_cfg_output(SPEAKER_PIN);
nrf_gpio_pin_clear(SPEAKER_PIN);