Nrf 52840 SPIM3 slew rate issue at 16 Mhz

[Sam-IIT]

I've been trying to communicate with an external device which supports up to 25 Mhz on its SPI. So, to improve performance, I'm using the SPI3 at 16 Mhz. I have no issue at 8 Mhz but, when doubling the speed, the slew rate on the clock behaves weirdly. 

I'm also using a fast-GPIO to be safe (P 0.21), but it did not have any effect on it. I'm configuring the SPI through the nrfx interface and the oscilloscope correctly detect the speed of 16 Mhz, but of course the data is corrupted due the clock behavior. I also switch the CS manually to improve its performances, but no luck.

Is there any extra configuration that I should be aware of?

[Turbo J]

Check that high drive mode is enabled in DTS overlay: Its the nordic,drive-mode = <NRF_DRIVE_H0H1>; entry in the pin confg group.

This setting is not enabled by default. You can also check the corresponding pin cfg bits in the debugger.

[Sam-IIT]

That did the trick, thanks! Is there any documentation about this point? I still get some weird data and I want to check if I'm missing something else.

[Turbo J]

You probably missed the errata that makes the fast SPI peripherial basically unusable on an NRF52840.

[Sam-IIT]

do you mean the CONFIG_NRF52_ANOMALY_198_WORKAROUND ? in that case i do have it in my conf file. if there is something different could you point me to it? thanks!