nrf52840 load capacitor

[Nop Microwave]

Hello,

I need to set very fine tunning on the 32 MHz oscillator frequency in order to get syncrhronisation on multiples devices using th Timer.

I there any register that can be used to set 32 MHz IC (inside) load capacitance, in parralele with external capacitor ?

Thanks

Nop

[ketiljo]

Hi Nop

No, there are no adjustments that can be made in FW. But given that the radio requires the HFXO to be within 30 ppm, do you really need much better accuracy for the timer? If this is a hard requirement, you need to use crystals with better tolerance. Also use high accuracy load caps or even consider using a TXCO.

[Nop Microwave]

Hi

Thanks for this answer. I need accuracy with ~ 1 PPM resolution between nodes in a network. Up to now, I adjust timer compare values to adjust Timers nodes in the network.

Is there any register that can read CFO (Carrier Frequency Offset) in the radio peripherical ?

Thanks.

Nop

[ketiljo]

To get CFO, you need a reference to something. As the system clock is what it is, you can't use that There's no feedback on the offset of the received signal either if that's what you mean. The transceiver isn't designed for this kind of use. The only possible solution would be to use a very accurate external oscillator. But those aren't cheap.

The radio peripheral is clocked at 16 MHz so at best, you will get 1 bit resolution on the timing, 62.5 ns

[Nop Microwave]

Thanks a Lot,

I was in fact talking about the receiver CFO.

[ketiljo]

The receiver doesn't have that.