This may be an obvious question, but I wanted to make sure that my assumptions are correct.
The nRF51822 is able to use an external 32kHz crystal oscillator for its low-frequency clock. The nRF51 series reference manual also mentions that other clock sources are possible:
The 32.768 kHz crystal oscillator is also designed to work with one of the following alternative external sources:
- A rail-to-rail clock signal applied to theXL1pin. The XL2 pin shall then be left unconnected.
- A low swing clock signal applied to the XL1 pin. The XL2 pin shall then be left unconnected.
I use sd_softdevice_enable() to start my low frequency clock. This function takes a Nordic-provided #define as a parameter describing the low-frequency clock source. However, none of the #defines describe the type of digital clock I'm using. They either describe the internal low frequency RC oscillator, a low frequency clock synthesized from the high frequency oscillator (which I've read on devzone is not recommended for use), or an external crystal.
When using a one of these non-crystal sources, which #defines should I use when calling sd_softdevice_enable()?
I'm assuming I should use a #define for an external crystal (e.g. NRF_CLOCK_LFCLKSRC_XTAL_20_PPM) with the same frequency stability as my source and the hardware will handle the rest, but I want to make sure.
Thanks Nordic folks!
