https://devzone.nordicsemi.com/f/nordic-q-a/5425/why-the-esb-ptx-example-does-t-have-any-clock-configThe Enhanced ShockBurst PTX Project just inits the ESB and start transmitting without ever configing either of the 16MHz or 32kHz clocks (none that I can see at least). Questions: Seems like both the 16MHz and the 32kHz clocks are disableden-USTelligent Community 13Thu, 05 Feb 2015 15:27:37 GMThttps://devzone.nordicsemi.com/thread/18927?ContentTypeID=1Thu, 05 Feb 2015 15:27:37 GMT137ad170-7792-4731-bb38-c0d22fbe4515:3f96b5ae-2c4e-4285-b8c4-93fbd161bb53Asbj&#248;rn<ol> <li>No, the 16 Mhz will be started by the ESB library when needed. It&#39;s hidden inside the library functions, but if you probe on the crystal, you&#39;ll see that it&#39;s started when the radio is transmitting. The 32 kHz is not needed for radio operation and will only be started if you need it from your application.</li> <li>Internal 16 Mhz RC oscillator for the MCU and external 16 MHz will be enabled when radio need it.</li> <li>Yes, SPI requires 16 MHz. You can request it to be started when you need it.</li> <li>You want to power down as soon as possible to save power. Powering down also means shutting down the clock sources. If you want to use the 32 kHz as a RTC source, that would be the lowest power consuming way to implement wakeup on timer.</li> </ol><div style="clear:both;"></div>