s110_nrf51822_6.0.0 limitaion, Synthesized low frequency clock source and calibrated RC

[Jan Krejsa]

Hello everyone, thx in advance for answers.

there is limitation written for 6.0.0 as follows:

Synthesized low frequency clock source is not tested or intended for use with BLE stack.

What does that mean? It will not work or it will, but it is not tested. I unerstand that this takes extra power consumption. How can I implement scenario with RC source and calibration?

1. How often do I need to perform calibration if I need to advertise for long period. Is the calibration made automatically?
2. Is there chance after connection is make to switch to synthetized clock?
3. Is possible to perform calibration during the ongoing connection?

Thx very much, Jan Krejsa

[Håkon Alseth]

Hi,

I think you're mistaking this option (NRF_CLOCK_LFCLKSRC_SYNTH_250_PPM) with the internal 32 kHz RC oscillator (NRF_CLOCK_LFCLKSRC_RC_250_PPM_xMS_CALIBRATION).

The Synthesized low frequency clock source is a 32.768kHz sourced from the 16M crystal. This will cause the systemon sleep current consumption to be much higher than if you're running on external 32k or using the internal RC 32k. The synthesized 32k-feature still works, but it is not covered by our internal test vectors.

1. If you're initializing the ble_stack with "NRF_CLOCK_LFCLKSRC_RC_250_PPM_*", then the stack will take care of the calibration routine for you, so you do not need to do any of this in your application space.

2. Not without disabling the stack.

3. Softdevice handles this for you.

Best regards Håkon