PWM on nrf52840

[saver]

i have just blinked the LED and trying to pwm 

i have written a simple led blinking program like this one below

#include <stdbool.h>
#include <stdint.h>
#include "nrf_delay.h"
#include "boards.h"
#include "nrf_gpio.h"

#define led_pin 27
/**
* @brief Function for application main entry.
*/
int main(void)
{
/* Configure board. */
nrf_gpio_cfg_output(led_pin);

while(1)
{
nrf_gpio_pin_toggle(led_pin);
nrf_delay_ms(500);
}

}

#####################################

a simple one, 

now i need to get to do pwm like short and sweet like this one 

---------most importantly i am using segger embedded studio---------------

can anyone tell how to do pwm in this nrf52840

please!!!

[Patrick]

Have you taken a look at the pwm examples included with the SDK? Particularly pwm_driver and pwm_library?

[saver]

they are actually really hard to understand,

can you give me a simpler code

           (OR)

where can i get the meaning or purpose for the commands given in the PWM library or pwm driver?

[Patrick]

PWM Library Documentation

PWM Driver Documentation

[saver]

can you give me a more simpler code the documentation is some what tough to understand.

[Einar Thorsrud]

Hi,

If you just want a simple PWM system, then you can use the PWM library. The example uses two breathing LEDs, but you can simplify it to one fixed LED glowing with 50 % intensity. Then the example could reduce to this:

#include <stdbool.h>
#include <stdint.h>
#include "nrf.h"
#include "app_error.h"
#include "bsp.h"
#include "nrf_delay.h"
#include "app_pwm.h"

APP_PWM_INSTANCE(PWM1,1);                   // Create the instance "PWM1" using TIMER1.

int main(void)
{
    ret_code_t err_code;

    /* 1-channel PWM, 200Hz, output on DK LED 1 pin. */
    app_pwm_config_t pwm1_cfg = APP_PWM_DEFAULT_CONFIG_1CH(5000L, BSP_LED_0);

    /* Switch the polarity of the second channel. */
    pwm1_cfg.pin_polarity[0] = APP_PWM_POLARITY_ACTIVE_HIGH;

    /* Initialize and enable PWM. */
    err_code = app_pwm_init(&PWM1,&pwm1_cfg, NULL);
    APP_ERROR_CHECK(err_code);
    app_pwm_enable(&PWM1);

    /* Set duty cycle to 50 % */
    while (app_pwm_channel_duty_set(&PWM1, 0, 50) == NRF_ERROR_BUSY);

    while (true)
    {
    }
}

[saver]

In pwm library i have some doubt to some commands

err_code = app_pwm_init(&PWM1,&pwm1_cfg,pwm_ready_callback);
APP_ERROR_CHECK(err_code);

and what are these things for

for (uint8_t i = 0; i < 40; ++i)
{
value = (i < 20) ? (i * 5) : (100 - (i - 20) * 5);

what is the purpose of this?

[saver]

pwm driver is better or pwm library is better?

why the pwm driver has 600 lines of code

can i get some simpler pwm driver code.

[Einar Thorsrud]

Hi,

This for loop creates the breathing effect by having the duty cycle change slowly.

[Einar Thorsrud]

The driver code (implementation) is provided as-is, and not intended to be used. When it comes to the WPM driver example that is also quite complex but remembers that the PWM peripheral is most sensible for more complex signals since it can "play out" a waveform from RAM via DMA etc. If you just want a simple to use PWM implementation then the PWM library is just as good in most cases (provided you have available TIMER, PPI and GPIOTE channels).