nRF52832 external crystals needed or not

RE: nRF52832 external crystals needed or not

Mattias — Wed, 02 Aug 2017 07:16:00 GMT

Thanks! I understand your comment about using a general purpose MCU. If the configuration in the final product will be as I described in my question this will probably be the case. At the moment we are in an early concept evaluation phase and want a prototype that can support different configurations with minor changes (e.g. add crystal and support BLE in unit B).

RE: nRF52832 external crystals needed or not

endnode — Tue, 01 Aug 2017 14:28:39 GMT

Hi Mattias,

There are like dozens of similar questions on the forum but let's go through it again;)

You always need external HF clock source on nRF52, no exceptions (more about that in last point).
You don't need to have LF external clock source but then you are either on "power hungry and not officially supported for Nordic BLE stack" synthesized clock from HF or on internal RC which need some SW routine to periodically calibrate. There are many hints on infocenter and this dev zone about this so it should be still safe way.
The same as previous point.
I believe that running nRF52 on internal HF clock (which is normally used only before external 32MHz crystal is stable and can be used) is highly not recommended. You can probably run nRF2 on it but that means you cannot use radio which brings the question: why would anyone on Earth use chip dedicated for BLE for something else when any general purpose ARM Cortex-M MCU can be used instead?;) Just with STM32 product line you get cheaper, smaller, more power effective (when you don't need 2.4GHz radio) and smaller PCB footprint items, similar with other vendors...

Cheers Jan

RE: nRF52832 external crystals needed or not

RK — Tue, 01 Aug 2017 14:24:18 GMT

yes
no - but you'll get possibly bad RTC accuracy with the LC oscillator. If you don't care that 10ms becomes 12ms, that's not an issue.
you do not
you do not, the unit will run off RC for as long as you like. Might find UART timing at high baud rates a bit interesting, but it'll run

you can test all this stuff with the dev kit by just writing code which doesn't even turn the LF or HF crystal oscillators on.