Radio Test - transmitter example

[TigerD]

Hi,

I have nRF52840 DK, and using nRF SDK v17. I am trying to understand radio transmitter example sendpacket().

RTC(1) seems to be used to the transmitting packet.

ret_code_t app_timer_init(void)
{

   ...
    err_code = NRF_ATFIFO_INIT(m_req_fifo);
 
    err_code = drv_rtc_init(&m_rtc_inst, &config, rtc_irq);

    drv_rtc_overflow_enable(&m_rtc_inst, true);
    drv_rtc_compare_set(&m_rtc_inst, 1, DRV_RTC_MAX_CNT >> 1, true);
    if (APP_TIMER_KEEPS_RTC_ACTIVE)
    {
        drv_rtc_start(&m_rtc_inst);
    }

    m_global_active = true;
    return err_code;
}

If I comment out  (In main.c)    err_code = app_timer_init();  it will stop sending radio packet. 

I traced rtc timer  (in app_timer2.c), all the following functions related to RTC(1) timer are not called (break points don't hit)

void rtc_update(drv_rtc_t const * const  p_instance); 

void timer_req_process(drv_rtc_t const * const  p_instance);

void rtc_irq(drv_rtc_t const * const  p_instance);

void timer_request_proc_trigger(void);

ret_code_t timer_req_schedule(app_timer_req_type_t type, app_timer_t * p_timer);

What is the role of this timer in the sending of radio packets?

Thank you,

David Zhou

[TigerD]

Hi Marte,

I have an urgent question, I would like to turn on DCDC regulator. In the radio_cmd.c file, (radio_test, or transmitter projects),

void toggle_dcdc_state(uint8_t dcdc_state)
{
    if (dcdc_state <= 1)
    {
        NRF_POWER->DCDCEN = dcdc_state;
    }
}

But in this link:

https://devzone.nordicsemi.com/f/nordic-q-a/33233/enable-dc-dc-regulator-without-an-external-lc-filter

and PDF document states that it needs internal LC filter.

So why it the toggle_dcdc_state function simply turns on DCDCEN regulator without ensuring LC filter? Is the LC filter on the nRF52840 DK board always connected?

Or simpler question: NRF_POWER->DCDCEN =0 or 1 is save to the DK board?

Otherwise, how to turn on the LC filter?

OK, I set it anyway.

NRF_POWER->DCDCEN = POWER_DCDCEN_DCDCEN_Enabled << POWER_DCDCEN_DCDCEN_Pos;

It seems working ok.

Thank you,

David Zhou

[Marte Myrvold]

Hi David,

TigerD said:

Or simpler question: NRF_POWER->DCDCEN =0 or 1 is save to the DK board

Setting DCDCEN to 1 enables the DC/DC regulator for REG1 stage.

If you do not connect an external LC filter when DC/DC regulator is enabled you might damage the chip. Please see the reference circuitry for the nRF52840 SoC. When looking at the different circuit configurations, you will see that when DCDCEN0 and/or DCDCEN1 are enabled there are LC filters connected for each of the DC/DC regulators, such as the inductor L4 between VDD and DCCH in circuit configuration no. 4.

Best regards,

Marte

[TigerD]

Thank you Marte,

David Zhou