SPI peripheral clock and frequency question

RE: SPI peripheral clock and frequency question

debbietray — Wed, 13 Feb 2019 16:58:53 GMT

Great, thanks for the quick responses and help!

RE: SPI peripheral clock and frequency question

Einar Thorsrud — Wed, 13 Feb 2019 11:24:40 GMT

Hi,

Yes, you are right. I was not aware, but this does not work with the higher clock frequencies supported by SPIM3. Then you are unfortunately stuck with either 8 MHz or 16 MHz.

RE: SPI peripheral clock and frequency question

debbietray — Tue, 12 Feb 2019 17:10:29 GMT

Hi Einar,

Thanks for the quick reply. Do you have more information on how I can tweak the frequency register? I tried several various settings for the frequency register, but when it wasn't recognized as one of the preset frequencies, it seemed to always default to 32MHz. Thanks!

RE: SPI peripheral clock and frequency question

Einar Thorsrud — Tue, 12 Feb 2019 08:47:09 GMT

Hi,

We have not tested anything other than the frequencies specified in the documentation for the FREQUENCY register. The supported frequencies can be exactly generated from the HF clock, so that you will have a stable clock signal with 50 % duty cycle.

You can try to tweak the FREQUENCY register, but as you can see by checking the CLK signal on a logic analyzer it will not be very clean. It might not be OK for the internal timing of your slave device, and it might not be OK for the nRF SPIM peripheral itself. Moreover, even if it does work it might be that it is only just, so that it might fail in some occasions on some devices.