nRF5340 clock sources

[Hiihtaja]

Hello !

It is not so clear default clock sources on nRF5340 app and net cores.

1.

As zephyr clock sources, SYSTICK timers are in use in both cores and timer clocking from external 32kHz XTAL oscillator.

Is this so ?

Should I specify  CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=y in prj.conf this line and for what core ?

2. RTCx timers is not used by default.

if I need to use those ( RTC0 on app core, RTC1 on net core), I should specify CONFIG_CLOCK_CONTROL_NRF_K32SRC_XTAL=y on both core's configuration ?

3. App core CPU clock is 128Mhz by default.

How to be sure if it clocked from XTAL oscillator ?

How to change clock to 64Mhz ?

4. Net core CPU clock is 64 Mhz by default.

How I be sure if it clocked from crystal oscillator ?

I can see clock_init() what use

clk_mgr = z_nrf_clock_control_get_onoff(CLOCK_CONTROL_NRF_SUBSYS_HF);

Should I use this code for app core as well or only on net core ?

On net core I use NRF_TIMER2 and RADIO and they need to be clocked form HF XTAL.

Regards,

Eugene

[Jared]

Hi,

It's best to specify for each core what clock source they should run at. 

The RTC is not a viable clock source for the Low Frequency Controller. 

The documentation states:

Each core has a number of low frequency clock (LFCLK) control instances. Each instance distributes one or more clocks to the core.

The LFCLK control instance in each core distributes the 32.768 kHz PCLK32KI peripheral clock to its corresponding core. The LFCLK clock is sourced from the power and clock subsystem to each LFCLK control instance.

In order to generate the LFCLK clock, the LFCLK controller uses the following LFCLK sources:
32.768 kHz RC oscillator (LFRC)
32.768 kHz crystal oscillator (LFXO)
32.768 kHz synthesized from HFCLK (LFSYNT)

The RTC will run off the LFCLK.

When started, the RTC will automatically request the LFCLK source with RC oscillator if the LFCLK is not already running.

You can check what clock source the LFCLK is running at by checking the LFCLKSTAT register.

regards

Jared 

[Hiihtaja]

Hi Jared !

But what about HFLK XTAL. Should I do some enabling of it ?

Some radio samples requiest it by _nrf_clock_control_get_onoff(CLOCK_CONTROL_NRF_SUBSYS_HF);

other not.

Regards,

Eugene

[ovrebekk]

Hi Eugene

Thanks for the detailed description, now I understand the issue more clearly. 

What you say is correct. The DPPI implementation in the nRF53 has a limitation that the PPI controller in the nRF52 doesn't have, and this is the fact that a task can only publish to one DPPI channel at a time, and an event can only subscribe to one DPPI channel at a time.  

So while a single channel can have an unlimited number of subscriptions or publishers, a single subscriber or publisher can only connect to a single DPPI channel. 

This does mean that there are certain PPI configurations that can not be properly duplicated using the DPPI controller. 

In order to connect the READY, ADDRESS and END events of the radio to the CAPTURE1 task you need to use a single DPPI channel for this, which means you can't easily disable one or the other connections. 

Do you have 2 free CC registers in the timer? 
If so, would it be an alternative to use separate CC registers for READY, ADDRESS and END?

Best regards
Torbjørn

[Hiihtaja]

Hi Torbjorn !

Thank you !

This is explain behaviour what I have. Does it really written in DS or other document somewhere ?

I will try to use different timers channel but I should rearrange code a bit.

Could you point me to sample where 3 events are  attached to one channel /single task ?

What I should do with other case :

NRF_RADIO_EVENT_ADDRESS -> NRF_TIMER_TASK_CAPTURE1

NRF_RADIO_EVENT_ADDRESS -> NRF_CCM_TASK_CRYPT

It looks as simple fork but again the same event should force 2 tasks and ADDRESS can be part of group

where 3 events force one task.

How you handle those cases in your SoftDevices.

Can EGU peripheral be used as proxy  in those cases and simplify these ?

Regards,

Eugene

[ovrebekk]

Hi Eugene

Hiihtaja said:

This is explain behaviour what I have. Does it really written in DS or other document somewhere ?

The difference between PPI and DPPI is not really documented. You would need to read the PPI and DPPI chapters in the respective product specifications and understand that there is an architectural difference between the two, even though they essentially do the same thing. 

Hiihtaja said:

Could you point me to sample where 3 events are  attached to one channel /single task ?

All you have to do is have 3 events publish to the same DPPI channel. 

Hiihtaja said:

What I should do with other case :

NRF_RADIO_EVENT_ADDRESS -> NRF_TIMER_TASK_CAPTURE1

NRF_RADIO_EVENT_ADDRESS -> NRF_CCM_TASK_CRYPT

i think your EGU proxy idea will work, yes. 

Essentially you have to use one DPPI channel to connect RADIO_EVENT_ADDRESS to two distinct EGU TASKS, for instance EGU_TASK_TRIGGER[0] and EGU_TASK_TRIGGER[1].

At this point you have basically converted the single ADDRESS event into two events (EGU_EVENT_TRIGGERED 0 and 1) which will both happen when the ADDRESS event occurs. 

Then you can use two more DPPI channels to connect EGU_EVENT_TRIGGERED[0] to TIMER_TASK_CAPTURE1, and EGU_EVENT_TRIGGERED[1] to CCM_TASK_CRYPT. 

These last two DPPI channels can then be assigned to groups, allowing you to enable and disable them easily. 

Best regards
Torbjørn

[Hiihtaja]

Hi Torbjorn !

In DS written

"One event can trigger multiple tasks by subscribing different tasks to the same channel."

It means I should be able to map address event to 3 tasks at list

nrf_radio_publish_set(NRF_RADIO, NRF_RADIO_EVENT_ADDRESS, ppi_radio_events_address);

nrf_timer_subscribe_set(NRF_TIMER2, NRF_TIMER_TASK_CAPTURE4, ppi_radio_events_address);

nrf_ccm_subscribe_set(NRF_CCM, NRF_CCM_TASK_CRYPT, ppi_radio_events_address);

For what reason I need EGU in this case ?

Regards,

Eugene

[ovrebekk]

Hi Eugene

If you want to have all three tasks connected to the ADDRESS event all the time then there is no need to use the EGU. 

But if you need to change dynamically which tasks get activated on the ADDRESS event and which does not, then you will need to use the EGU, since the DPPI does not allow an event to publish to two different DPPI channels at the same time. 

Best regards
Torbjørn

[Hiihtaja]

Hi Torbjorn !

I also can see that one event can be distributed to multiple tasks easily by using one channel.

I will try to add to the same channel GPIOTE task for toggle external GPIO line.

Regards,

Eugene

[ovrebekk]

Hi Eugene

Sounds good. If you have any more questions or comments just let me know. 

Best regards
Torbjørn

[Hiihtaja]

Hi Torbjorn !

Does gpiote task is also can't be added in 2 places ?

I create GPIOTE task for toggle GPIO pin and would like to measure TX frame duration between READY and END events.

nrfx_gppi_fork_endpoint_setup(ppi_radio_event_ready, nrfx_gpiote_out_task_addr_get(DBG_PIN5));

nrfx_gppi_fork_endpoint_setup(ppi_radio_event_end, nrfx_gpiote_out_task_addr_get(DBG_PIN5));

nrfx_gpiote_out_task_enable(DBG_PIN5);

Should it work or not ?

Regards,

Eugene

[ovrebekk]

Hi Eugene

It should be possible to associate two different events with the same GPIOTE OUT task, yes. 

Are you not able to get it to work? 

If so, could you try using the nrfx_gppi_task_endpoint_setup(..) function instead and see if it works better?

Best regards
Torbjørn

[Hiihtaja]

Hi Torbjorn !

It dosn't work for me.

But looks like SET and CLR tasks are created automatically and I can use OUT or SET with READY_EVENT and CLR with END event.

Can it be counted as right solution as well OR better try to use OUT task twice ?

and nrfx_gppi_task_endpoint_setup(..) ?

I use like this now.

nrf_radio_publish_set(NRF_RADIO, NRF_RADIO_EVENT_READY, ppi_radio_event_ready);

nrf_timer_subscribe_set(NRF_TIMERX, NRF_TIMER_TASK_CAPTURE1, ppi_radio_event_ready);

uint32_t channels_mask = BIT(ppi_radio_event_ready);

and attach different GPIO lines ( RX and TX activity ) after that as usually :

if (is_tx) {

nrfx_gppi_fork_endpoint_clear(ppi_radio_event_ready, nrfx_gpiote_set_task_addr_get(DBG_PIN6));

nrfx_gppi_fork_endpoint_setup(ppi_radio_event_ready, nrfx_gpiote_set_task_addr_get(DBG_PIN5));

nrfx_gpiote_out_task_enable(DBG_PIN5);

 

} else {

nrfx_gppi_fork_endpoint_clear(ppi_radio_event_ready, nrfx_gpiote_set_task_addr_get(DBG_PIN5));

nrfx_gppi_fork_endpoint_setup(ppi_radio_event_ready, nrfx_gpiote_set_task_addr_get(DBG_PIN6));

nrfx_gpiote_out_task_enable(DBG_PIN6);

}

I will also try to use RXREADY and TXREADY events instead of READY,( I have radio shortcut READY)

Regards,

Eugene