Can the nRF52840 use other clock frequencies than 64 or 32 MHz?

[henryh]

I'd like to clock the nRF52840 at the same frequency as my converters. Is there any problem with using a somewhat different frequency than the 64 MHz (or 32mhZ) crystal? If it is OK, what is the permissible frequency range?

[endnode]

nRF52840 specification is clear: similar to all other nRF5x chips only specific high-frequency clock source is possible (and required if you want to use 2.4GHz radio interface). In case of nRF52840 it is 64MHz crystal.

[Turbo J]

The radio will only work with the correct crystal.

If you don't need the radio, you would be better off using a different chip. The crystal oscillator is tailored not just for the specified frequency but also for a rather fast startup time <1ms. This usually results in a very narrow range of allowed crystal frequencies.

Oh, and switching from the internal 64 MHz RCO to the crystal based osc and back would more likely produce glitches that can cause various errors - even if you get the crystal running.