Avoid SDK modules who need app timers

RE: Avoid SDK modules who need app timers

Susheel Nuguru — Fri, 13 Apr 2018 05:45:02 GMT

When softdevice is enabled using it will use the RTC0 interrupts for time keeping with highest priority. So your application timers will be affected with it since your application timers are running with lower priority than softdevice timer (RTC0)

What you see is normal

RE: Avoid SDK modules who need app timers

Sumanth Murali — Sat, 07 Apr 2018 04:26:47 GMT

Starting LF clock using nrf_drv_lf_clk_request() instead of SOFTDEVICE_HANDLER_INIT changes the timing of the system. Interrupts come in at a different rate. Any idea why this could be happening?

RE: Avoid SDK modules who need app timers

Susheel Nuguru — Mon, 30 Jan 2017 16:55:15 GMT

if the app_timer was using the same LFCLK as softdevice will be using, then there will be no problem. But if you ask the softdevice to switch to other (for example from RC to XTAL) then the switch might cause a temporary glitch in the app_timer accuracy

RE: Avoid SDK modules who need app timers

bloobird0 — Fri, 27 Jan 2017 08:39:12 GMT

Hello, what is the softdevice is present but not activated, LFCLK started manually like described above and later SOFTDEVICE_HANDLER_INITis called. Is there any probleme there that the SoftDevice tries to start a clock that is already in use by app_timer?

RE: Avoid SDK modules who need app timers

ppatierno — Tue, 28 Jul 2015 13:43:50 GMT

Great to know Aryan !

I'm using SoftDevice S130 and I was scaried that without external oscillator (on our target board for a wereable) I couldn't use the great app timers feature. Now I know that I can use them for my project.

Thanks, Paolo

RE: Avoid SDK modules who need app timers

Susheel Nuguru — Tue, 28 Jul 2015 13:42:25 GMT

copy paste from reference manual about the options you have to choose from for LFCLK

LFCLK clock controller
As illustrated in Figure 15 the system supports the following low frequency clock sources:
• LFCLK crystal oscillator: 32.768 kHz crystal oscillator
• LFCLK RC oscillator: 32.768 kHz RC oscillator
• LFCLK synthesizer: 32.768 kHz synthesized from HFCLK

If you do not have the first one on your product, you can choose the others. Read about clocks before you make major changes to your code.

RE: Avoid SDK modules who need app timers

Susheel Nuguru — Tue, 28 Jul 2015 13:36:37 GMT

Normally with softdevice, you select the LFCLK when you call SOFTDEVICE_HANDLER_INIT

In your case you call for example

SOFTDEVICE_HANDLER_INIT(NRF_CLOCK_LFCLKSRC_RC_250_PPM_4000MS_CALIBRATION, NULL);

Then softdevice will start the LFCLK for your application. If your application does not use softdevice then you can do this in your app like below

NRF_CLOCK->LFCLKSRC            = (CLOCK_LFCLKSRC_SRC_RC << CLOCK_LFCLKSRC_SRC_Pos);
NRF_CLOCK->EVENTS_LFCLKSTARTED = 0;
NRF_CLOCK->TASKS_LFCLKSTART    = 1;

while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0)
{
    // Do nothing.
}
    
APP_TIMER_INIT(APP_TIMER_PRESCALER, APP_TIMER_MAX_TIMERS, APP_TIMER_OP_QUEUE_SIZE, NULL);

And the APP_TIMER will use internal oscillator, you just need to select and start the LFCLK once

RE: Avoid SDK modules who need app timers

ppatierno — Tue, 28 Jul 2015 13:25:13 GMT

Hi Aryan, I'm new to the Nordic platform so some features are new to me. Do you mean that I can use the app timers without external oscillator for RTC1 so that I can avoid to change the entire application ? Can you give me more tips or reference about that ?

Thanks, Paolo.

RE: Avoid SDK modules who need app timers

Susheel Nuguru — Tue, 28 Jul 2015 13:09:34 GMT

Why are you not using internal RC LFCLK?