I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Sigurd — Tue, 24 Oct 2017 11:32:14 GMT

No, the LFCLK runs at 32 kHz, so you can not get a 50% duty PWM at 33.33khz with the LFCLK.

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Yashur — Tue, 24 Oct 2017 11:27:39 GMT

@Sigurd Isn't there a way to produce this frequency clock using LFCLK?

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Sigurd — Thu, 12 Oct 2017 14:02:24 GMT

You could use the PWM library, this will allocates a timer instance and consume 2+4 PPI channels, 1 PPI group, and 2 GPIOTE channels. I.e. it will use more of the resource on the chip to use the PWM library than the PWM peripheral. If this is not a problem for your application, then you can use the PWM library instead if you want.

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Yashur — Thu, 12 Oct 2017 13:54:57 GMT

Hey Sigurd may i know the reason you suggested PWM peripheral in the first place? why didn't my code work?

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Sigurd — Fri, 06 Oct 2017 13:12:28 GMT

Hi,

All the driver API is documented at infocenter here.

Since you need 33.33KHz you need to use the HFCLK anyway. The low-power PWM library that uses the LFCLK have a max frequency around 6kHz.

To save power, add this to the loop to put the CPU to sleep:

for (;;)
{
    // Use directly __WFE and __SEV macros since the SoftDevice is not available.
    // Wait for event.
    __WFE();

    // Clear Event Register.
    __SEV();
    __WFE();
}

you could also remove the code in start of main(), i.e. the NRF_CLOCK->TASKS_HFCLKSTART = 1; and while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);. Then you will be using the HFINT(internal HF RC) instead of the HF crystal oscillator(HFXO), you will get lower power consumption with HFINT. With this, I'm measuring around 680 µA.

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Yashur — Fri, 06 Oct 2017 12:10:04 GMT

Okay! I'll check and get back to you! Thank You! How do a beginner understand all the api's? and Why did you suggest pwm peripheral? and your code uses high frequency clock! Isn't there a better way to consume less power?

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Sigurd — Fri, 06 Oct 2017 12:06:00 GMT

Make sure that the code is exactly the same as in my post, and try to rebuild your project.

Here is a .hex generated from the above code. It should give 50% duty cycle on PIN 4.

nrf52832_xxaa_PWM.hex

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Yashur — Fri, 06 Oct 2017 12:01:05 GMT

I need 50% duty cycle and i'm getting only 25! My SDK version is 14 and it's a nRF52832 board and not a custom board!

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Sigurd — Fri, 06 Oct 2017 11:57:24 GMT

What duty cycle are you measuring? What SDK version are you using? Is this a nRF52-DK or a custom board?

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Yashur — Fri, 06 Oct 2017 11:53:50 GMT

No, I'm not using Kiel . I'm using windows command prompt! I have got the code running by changing makefile! adding nrf_drv_pwm.h files etc..But the code doesn't give a 50% duty cycle signal!

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Sigurd — Fri, 06 Oct 2017 07:28:32 GMT

Are you using Keil? Then you need to add the driver to the project, and add the path to the "Include paths".

But, e.g. the pwm_driver example should already have all the included paths and files added. The pwm_driver example is located in the folder <SDK_InstallFolder>\examples\peripheral\pwm_driver. Just remove everything in main.c, and add the code I posted instead.

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Yashur — Fri, 06 Oct 2017 05:50:47 GMT

Hey ! Thanks for your support! But i'm getting a compile error saying "nrf_drv_pwm.h" file as not found! May i know how to fix this?

RE: I have tried to produce a PWM signal of 33.33KHz at a GPIO pin of nRF52832!The duty cycle of the signal varies bizzaredly even after setting it to 50%!Can anyone help me out! I wanna run an external IC on this clock!Please find the screenshot attached!

Sigurd — Thu, 28 Sep 2017 07:51:42 GMT

Hi,

I recommend that you use the PWM peripheral for this.

The code below will give you a 33.33 KHz clock at 50 % duty at pin 4.

#include <stdio.h>
#include <string.h>
#include "nrf_drv_pwm.h"
#include "app_util_platform.h"
#include "app_error.h"
#include "boards.h"
#include "bsp.h"
#include "nrf_drv_clock.h"
#include "nrf_delay.h"


#define OUTPUT_PIN 4

static nrf_drv_pwm_t m_pwm0 = NRF_DRV_PWM_INSTANCE(0);

// Declare variables holding PWM sequence values. In this example only one channel is used 
nrf_pwm_values_individual_t seq_values[] = {0, 0, 0, 0};
nrf_pwm_sequence_t const seq =
{
    .values.p_individual = seq_values,
    .length          = NRF_PWM_VALUES_LENGTH(seq_values),
    .repeats         = 0,
    .end_delay       = 0
};


static void pwm_init(void)
{
    nrf_drv_pwm_config_t const config0 =
    {
        .output_pins =
        {
            OUTPUT_PIN, // channel 0
            NRF_DRV_PWM_PIN_NOT_USED,             // channel 1
            NRF_DRV_PWM_PIN_NOT_USED,             // channel 2
            NRF_DRV_PWM_PIN_NOT_USED,             // channel 3
        },
        .irq_priority = APP_IRQ_PRIORITY_LOWEST,
        .base_clock   = NRF_PWM_CLK_1MHz,
        .count_mode   = NRF_PWM_MODE_UP,
        .top_value    = 30,
        
        //F(pwm) = F(clk)/top_value
        
        
        .load_mode    = NRF_PWM_LOAD_INDIVIDUAL,
        .step_mode    = NRF_PWM_STEP_AUTO
    };
    // Init PWM without error handler
    APP_ERROR_CHECK(nrf_drv_pwm_init(&m_pwm0, &config0, NULL));
    
    seq_values->channel_0 = 15;
    nrf_drv_pwm_simple_playback(&m_pwm0, &seq, 1, NRF_DRV_PWM_FLAG_LOOP);
    
}


int main(void)
{

    // Start clock for accurate frequencies
    NRF_CLOCK->TASKS_HFCLKSTART = 1; 
    // Wait for clock to start
    while(NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) ;
    
    pwm_init();

    for (;;)
    {
        
    }
}