PWM of nRF52805

RE: PWM of nRF52805

Jared — Thu, 15 Apr 2021 07:56:41 GMT

Great!!

To elaborate a bit more for anyone else that might be seeing this issue: HFXO is automatically used when you're using the radio. The chip will switch between using HFINT and HFXO based on the power requirement unless the HFXO is manually started. Starting the HFXO manually will always keep it on. The consequences of this is added power consumption. This might not be a significant drawback if you're already using PWM. You could try only enabling HFXO clock when you use PWM and then stop it after you're done using PWM.

If you don't use the Softdevice, then you can Start and Stop the HFXO by writing directly to the register:

Start:

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

Stop:

NRF_CLOCK->TASK_HFCLKSTOP = 1;

If you use the Softdevice, then you can Start and Stop the HFXO by requesting and releasing the clock:

Request:

    err_code = sd_clock_hfclk_request();
    APP_ERROR_CHECK(err_code);

    uint32_t hfclk_is_running = 0;

    while (!hfclk_is_running)
    {
        APP_ERROR_CHECK(sd_clock_hfclk_is_running(&hfclk_is_running) );
    }

Release:

    err_code = sd_clock_hfclk_release();
    APP_ERROR_CHECK(err_code);

The benefit of using the HFXO with PWM is that you'll get a higher accuracy then with the HFINT. The HFINT is specified as typical +- 1.5% but can be max +- 6%. This can create a significant variation between samples, and when the radio runs on (HFXO) and the PWM (HFINT).

You can read more about HFXO and HFINT here.

regards

Jared

RE: PWM of nRF52805

colijevia — Thu, 15 Apr 2021 01:40:47 GMT

Hi,

I tried,and the isseue is solved,now it works well,thank you.

regards，

colijevia

RE: PWM of nRF52805

Jared — Wed, 14 Apr 2021 11:43:33 GMT

Hi,

We're suspecting that the issue might be due to the difference in accuracy between the internal oscillator HFINT and the crystal oscillator HFXO (used by the softdevice). The PWM will run on HFINT unless the HFXO is explicitly started.

Could you try running the external oscillator from the start in main by adding this right after you have initialized the Softdevice?:

    err_code = sd_clock_hfclk_request();
    APP_ERROR_CHECK(err_code);

    uint32_t hfclk_is_running = 0;

    while (!hfclk_is_running)
    {
        APP_ERROR_CHECK(sd_clock_hfclk_is_running(&hfclk_is_running) );
    }

regards

Jared

RE: PWM of nRF52805

colijevia — Wed, 14 Apr 2021 09:20:52 GMT

HI,
sorry to reply so late,I tried with nrf52832 DK, but the same problem still exists.is there any other way for reference?

regards
colijevia

RE: PWM of nRF52805

Jared — Wed, 24 Mar 2021 13:58:51 GMT

Hi,

From the video that you shared it seems that there are some shifts in the signal when the noise happens. Are you able to reproduce the issue with app_pwm on a nRF52 DK or is just on the custom board that has nrf52805?

[quote user="colijevia"]Now, I simulate PWM by PPI and timer, but no matter on nrf52323 or nrf52810, the buzzer will also be interrupted.
[/quote]

This seems to indicate that you are able to reproduce it on another board? Please clarify, and specify if you're able to reproduce on a development kit or not.

regards

Jared

RE: PWM of nRF52805

colijevia — Mon, 22 Mar 2021 06:49:14 GMT

Hi，

Sorry to reply late,i use nRF52832 custom PCB ,Keil version5,SDK15.00,here are my code:
devzone.nordicsemi.com/.../7558.APP_5F00_PWM.rar
devzone.nordicsemi.com/.../2072.PPI_5F00_PWM.rar
Added a Oscilloscope test videos,noise will be heard:

devzone.nordicsemi.com/.../buzzer_5F00_test.mp4

Is this sound normal?

Best regards

colijevia

RE: PWM of nRF52805

Jared — Fri, 19 Mar 2021 10:08:18 GMT

Hi,

[quote user="colijevia"]Now, I simulate PWM by PPI and timer, but no matter on nrf52323 or nrf52810, the buzzer will also be interrupted.
[/quote]

So now you also see the issue on the other samples that have a different nRF52 IC?

Could you share the code that uses app_pwm that produces the issue?

RE: PWM of nRF52805

colijevia — Wed, 17 Mar 2021 09:51:53 GMT

Hi,
Sorry, I didn't notice that the program in 52832 added delay：

...
buzzer_power_on();
nrf_delay_ms(500);
buzzer_power_off();
...

I found that the buzzer is very stable only during the delay period 500ms.
Now, I simulate PWM by PPI and timer, but no matter on nrf52323 or nrf52810, the buzzer will also be interrupted.
My configuration is as follows:

static const nrf_drv_timer_t m_timer = NRF_DRV_TIMER_INSTANCE(1);
static nrf_ppi_channel_t m_ppi_channel;

void my_gpiote_init(void)
{
ret_code_t err_code;

err_code = nrf_drv_gpiote_init();
APP_ERROR_CHECK(err_code);

nrf_drv_gpiote_out_config_t out_config = NRFX_GPIOTE_CONFIG_OUT_TASK_TOGGLE(true);

err_code = nrfx_gpiote_out_init(BUZZER_PIN, &out_config);
APP_ERROR_CHECK(err_code);

nrf_drv_gpiote_out_task_enable(BUZZER_PIN);

}

static void PPI_event_init(void)
{
ret_code_t err_code;
err_code = nrf_drv_ppi_init();
APP_ERROR_CHECK(err_code);

nrf_drv_timer_config_t timer_cfg = NRF_DRV_TIMER_DEFAULT_CONFIG;
timer_cfg.bit_width = NRF_TIMER_BIT_WIDTH_32;

err_code = nrf_drv_timer_init(&m_timer, &timer_cfg, NULL);
APP_ERROR_CHECK(err_code);

uint32_t ticks = nrf_drv_timer_us_to_ticks(&m_timer, 125);
nrf_drv_timer_extended_compare(&m_timer,
NRF_TIMER_CC_CHANNEL0,
ticks,
NRF_TIMER_SHORT_COMPARE0_CLEAR_MASK,
false);

nrf_drv_timer_enable(&m_timer);
uint32_t timer_compare_event_addr =

nrf_drv_timer_compare_event_address_get(&m_timer,NRF_TIMER_CC_CHANNEL0);

uint32_t gpiote_task_addr = nrf_drv_gpiote_out_task_addr_get(BUZZER_PIN);

err_code = nrf_drv_ppi_channel_alloc(&m_ppi_channel);
APP_ERROR_CHECK(err_code);

err_code = nrf_drv_ppi_channel_assign(m_ppi_channel,
timer_compare_event_addr,
gpiote_task_addr);
APP_ERROR_CHECK(err_code);

ret_code_t err_code = nrf_drv_ppi_channel_enable(m_ppi_channel);

APP_ERROR_CHECK(err_code);

}

Best regards
colijevia

RE: PWM of nRF52805

Jared — Wed, 17 Mar 2021 09:15:59 GMT

[quote user="colijevia"]PPI function seems to be not working, it seems to be interrupted intermittently.[/quote]

PPI runs independently of the CPU and shouldn't be interrupted. Could you elaborate more on this?

If you probe the PWM signal on P0.16, how does it look like when you compare it with the samples that has a nRF52832?

RE: PWM of nRF52805

colijevia — Tue, 16 Mar 2021 11:17:31 GMT

Hi,
I used PIN P0.16，PPI function seems to be not working, it seems to be interrupted intermittently.

RE: PWM of nRF52805

Jared — Tue, 16 Mar 2021 08:31:21 GMT

Hi,

No, it shouldn't be problematic. app_pwm doesn't use the PWM peripheral, instead it uses bit-banging and a GPIO pin to produce a PWM signal.

What pins are you using?

regards

Jared

RE: PWM of nRF52805

colijevia — Tue, 16 Mar 2021 01:09:11 GMT

Yes, I didn't see PWM introduction in the chip manual, but I used it. Would that cause any problems?

Thank you.

RE: PWM of nRF52805

Jared — Mon, 15 Mar 2021 14:38:22 GMT

Hi,

Are you seeing this on all of your samples that have the nRF52805?

regards

Jared