RE: How to enable external clock

Vidar Berg — Fri, 21 May 2021 07:46:35 GMT

Hi,

The CLOCK_CONFIG_LF_SRC setting will only have an effect if you use the SDK clock driver, but it doesn't look like the ESB example use this driver. Another option to using the driver is to start the the crystal oscillator directly as shown in the code snippet below.

void clocks_start( void )
{
    // Start HFCLK and wait for it to start.
    NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
    NRF_CLOCK->TASKS_HFCLKSTART = 1;
    while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0);

    // Start LFXO and wait for it to start
    NRF_CLOCK->LFCLKSRC = CLOCK_LFCLKSRC_SRC_Xtal << CLOCK_LFCLKSRC_SRC_Pos;
    NRF_CLOCK->TASKS_LFCLKSTART = 1;
    while (NRF_CLOCK->EVENTS_LFCLKSTARTED == 0);
}