Baud rate for SPI

[Riccardo78]

Hi,

I have a question regarding the frequency of the SPI peripheral of the nrf52.

According to the Product Specification v1.4, the minimum value for the frequency is 125kbps, setting the register to 0x02000000

We have made a test with lower values and the spi peripheral seems to work fine.

Would it be possible to have your feedback about using lower values, not reported in the Product Specification document ?

Would it be possible to know the function f for f(clock_frequency) = Register Value, if exists ?

Thanks in advance for the support.

Kind regards

Riccardo

[Dmitry]

Hi Riccardo,

you can find the formula in this thread, it's the same for SPI.

[Riccardo78]

Hi Dmitry,

Thansk so much for the prompt reply. 

Is the formula described in the post also available in some official documents ?

Is there any problem/issue if we use a peripheral with a lower baudarate ?

Thanks again!

[Dmitry]

I didn't find it in official documents.. just can say that I used it to turn SPI interface into a simple tx-only UART, and it worked at 115200.

[Riccardo78]

Hi Dmitry,

Ok. Actually my goal it would be to use the spi peripheral at 2400 bps to implement a driver for the DALI protocol. So, if there are no official restrictions about lower baudarate, I might give a try.

Thanks again.

Kind Regards

Riccardo

[Riccardo78]

Hi Dmitry,

Once more thing.

I noticed that the Frequency register of the SPI is shared with TWI (I2C) one. But the values reported in the Product Specification v1.4 (see the image below) are different from the ones I obtained from the formula in the post. Are they computed with a different formula or am I doing something wrong ?

Values obtained through the formula in the post

Could you kindly give your feedback on those values please ?

Thanks in advance !

KR

Riccardo