NCS System On sleep without XO

RE: NCS System On sleep without XO

grahamm — Wed, 15 May 2024 13:45:14 GMT

I have found placing a k_usleep() in front of my k_sleep() allows the nRF to enter the expected power state. I'm not going to dig into it further as running without an XO is not standard configuration.

k_usleep(1);
k_sleep(K_MSEC(10));

RE: NCS System On sleep without XO

Priyanka — Mon, 13 May 2024 08:48:05 GMT

Hi Graham,

Please take a look at this ticket and maybe this might help for the power management.

Regards,

Priyanka

RE: NCS System On sleep without XO

grahamm — Fri, 10 May 2024 12:55:03 GMT

This is good info, thanks! It is acceptable that accuracy is comprised with only the LFRC. However if I dig into these posts, discussion relates to the NRF SDK. Can you give some guidance in configuring the RTC to use LFRC, and configure this ULP mode, in nRF Connect SDK?

RE: NCS System On sleep without XO

Priyanka — Fri, 10 May 2024 09:57:51 GMT

Hi,

Technically yes, the RTC can be configured to use the LFRC even without a LFXO. The LFRC is the default source of the LFCLK in Nordic devices. However, please do note that using LFRC may affect the accuracy and power consumption of the device.

Please take a look at this ticket, where it is mentioned that you might be able to use it, but with a compromised accuracy and power levels.

Also, you can see in the Product Specification, that LFRC oscillator has two modes of operation: normal and ultra-low power (ULP) mode, enabling the user to trade power consumption against accuracy of the clock. The LFRC oscillator has to be stopped before changing the mode of the oscillator. Also, the LFRC frequency will be affected by variation in temperature and the oscillator can be calibrated to improve accuracy by using the HFXO as a reference oscillator during calibration.

Regards,

Priyanka

RE: NCS System On sleep without XO

grahamm — Wed, 08 May 2024 14:45:55 GMT

Thanks for your response. I should have mentioned, we are not using the radio on this board. In NCS, can RTC be configured to use only the LFRC, without an LFXO present?

RE: NCS System On sleep without XO

Priyanka — Wed, 08 May 2024 13:45:16 GMT

Hi Graham,

Considering to not use the HFXO or LFXO will not allow you to use the RADIO. The HFXO is typically needed when you are using the radio, in which case there is a radio protocol running (e.g. Bluetooth). The radio protocol will automatically start and stop the HFXO when it needs a high accuracy clock.

Also, the LFXO is often used for Real Time Counter (RTC) applications. However, if the LFXO is tampered with or stopped, it can pause the watchdog and RTC peripheral, as well as the SoftDevice depending on the executed BLE functionality.

https://docs.nordicsemi.com/bundle/ps_nrf5340/page/chapters/oscillators/doc/oscillators.html#ariaid-title1

Rgards,

Priyanka