wt is the difference bw PWM driver and PWM Library example

[saiteja]

(/attachment/182b723590b3c447267d5aed62b5405f)hi, i want to work on PWM to controll the vibration coin frequency for certain time period and also to change RGB values of LEDs so which example i can choose to understand PWM on nRF52.

#Edit:- /* Switch the polarity of the second channel. */ //pwm1_cfg.pin_polarity[1] = APP_PWM_POLARITY_ACTIVE_HIGH;

   /* Initialize and enable PWM. */
   err_code = app_pwm_init(&PWM,&pwm1_cfg,pwm_ready_callback);
   APP_ERROR_CHECK(err_code);
   app_pwm_enable(&PWM);

   uint32_t value;

      APP_ERROR_CHECK(err_code);
   while(true)
   {

       for (uint8_t i = 0; i < 40; ++i)
       {
           value = (i < 20) ? (i * 5) : (100 - (i - 20) * 5);
           //printf("value = %d\n",value);
           ready_flag = false;
           /* Set the duty cycle - keep trying until PWM is ready... */
           while (app_pwm_channel_duty_set(&PWM, 0, value) == NRF_ERROR_BUSY);

           /* ... or wait for callback. */
           while(!ready_flag);
           APP_ERROR_CHECK(app_pwm_channel_duty_set(&PWM, 1, value));
           nrf_delay_ms(50);

       }

   }

[Jørn]

Hello saiteja

The PWM driver and library provide two ways of generating a PWM signal on the nRF52. The PWM driver uses dedicated hardware to generate the signal, while the PWM library uses GPIOTE, PPI and timers in combination.

For more information on the two and their properties please see the following links to the infocenter

PWM driver (dedicated hardware):

infocenter.nordicsemi.com/index.jsp

PWM library (GPIOTE, PPI and timers):

infocenter.nordicsemi.com/.../lib_pwm.html

You can find links to descriptions of the examples you mentioned (pwm_driver and pwm_library in the examples->peripheral folder) on the pages of the infocenter links above.

Best regards

Jørn Frøysa

[saiteja]

hey thank you for your time, as per my requirement i want to drive a vibrator for few seconds with defferent frequencies through a GPIOTE so that i need to use PWM Library right?

[saiteja]

and also when i drive a GPIOT pin using PWM library (the code shown above Edit:- ) i was stuck in while loop that means it keep on giving PWM signal. with max voltage varying between 2.5v to 0v. the problem is 1)i need to drive GPIOT only for few seconds. 2)when i connect vibrator( C0820B006F) through MOSFET LPF it is unable to vibrate.

[Jørn]

You can use either the PWM driver with its dedicated hardware or you can use the PWM library.

In the PWM library example you can change the frequency of the PWM signal by uninitializing the PWM instance, changing the .period_us value in pwm1_cfg, and then initializing the PWM instance again.

The while loops in the example are used to change how quickly the leds ramp up and down by changing the duty cycle of the PWM signal. These are not needed if you only intend to change the frequency.

To only send for a few seconds you can use a timer, and in the callback function you can stop the PWM and change its frequency if needed.

What voltage do you have on the output of your LPF? According to the datasheet of the C0820B006F it has an operating voltage requirement of 2.7 – 3.3 V DC.

Best regards

Jørn Frøysa

[saiteja]

hi, i have connected LPF but the motor not vibrating. i am drived GPIO pin as PWM. if i observe the GPIO pin voltage its varying from 2.8 volts to 0 volts.

[Jørn]

The maximum output voltage from GPIO on the nRF52 series is VDD, so your maximum output voltage is dependent on the supply voltage. You need to make sure the output voltage from your low pass filter is within the specifications of your motor (2.7-3.3 V DC), considering your maximum PWM voltage is 2.8 V you may need to amplify the output of the filter.