I heavily recommend you to use other GPIO pins if you have the opportunity. Using the external 32 kHz crystal will give you much lower average current consumption than using the RC oscillator.
Anyways, here is a link showing the SB1,SB2,SB3 and SB4.
For using the RC oscillator, you need to use NRF_CLOCK_LF_SRC_RC as a clock source. You normally do this in the function ble_stack_init()
I heavily recommend you to use other GPIO pins if you have the opportunity. Using the external 32 kHz crystal will give you much lower average current consumption than using the RC oscillator.
Anyways, here is a link showing the SB1,SB2,SB3 and SB4.
For using the RC oscillator, you need to use NRF_CLOCK_LF_SRC_RC as a clock source. You normally do this in the function ble_stack_init()
Let's say that you in RX uses 9.2mA, and the LFRC oscillator is configured to 500ppm, and the alterative LF crystal is 20 ppm. Then you have a 480 ppm diff, which gives you an average increase at ~4,5 µA. Adding 2µA for calibrating the LFRC oscillator at 4 seconds interval, gives you in total a 6,5µA increase approximately.
