Chip/Ceramic antenna plus external crystal

[Raja]

I am planning to use MDBT42Q with Chip/Ceramic antenna. I can see in the data sheet they have mentioned an optional 32.768khz crystal.

see page 32 (8. Reference Circuit): statics3.seeedstudio.com/.../MDBT42Q-Version_B.pdf

Now in order to use the optional 32.768khz crystal in code should i use this setting?

SOFTDEVICE_HANDLER_APPSH_INIT(NRF_CLOCK_LFCLKSRC_XTAL_20_PPM, true);

Also i wanted to clarify with this optional crystal will we have now 3 crystals in total. One in nrf52 chip, second in MDBT42Q and third in our pcb board?

So what do other 2 Crystals do if application is using this optional external crystal?

[RK]

No. There are at max only two crystals and the crystal has nothing at all to do with the antenna.

The MDBT42Q has one HF crystal on it (required). It doesn't have the optional 32kHz crystal on the board, if you want to use an external crystal, you have to supply it. There is no 32kHz crystal 'in the nrf52 chip'. The chip has an internal RC oscillator.