Can you I use 16Mhz internal clock to run peripheral uart example? With out using / having any external clock on nrf51422?

Question

Hi,
Can i use internal 16Mhz clock of nrf51822, to run peripheral uart example? I don't want to use any external clocks? 
 If yes what are the changes i need to make in example peripheral uart project? 
 Thanks and Regards,
Faizan

MartinBL · Accepted Answer

Hi 
 Both nRF51 and nRF52 have an internal clock manager that automatically handles the high and low frequency clocks. The manager will automatically start the internal RC oscillator (RC) whenever a peripheral needs a clock source. To save power the manager will also turn it off again when it is not needed anymore. Regarding the external crystal (XTAL), it is actually only required in special circumstances. E.g. the radio needs a frequency with higher accuracy than the RC can provide and hence you need the XTAL. The analog modules like the ADC also use the XTAL to get more accurate measurements. Beyond that, most of the other peripherals, including the UART, will automatically be clocked by the RC if you have not explicitly started the XTAL. If you choose to start the XTAL the manager will turn off the RC automatically. 
 If you don't use the radio you don't actually need an XTAL at all, everything else will work. 
 Clock manager documentation for nRF51 can be found in the Reference Manual V3.0, Ch 13 .