NRF52 GPIO located near the radio

[liron]

Its stated in the Product Spec that one shouldn't place high frequency or high sink/source IO at GPIOs 22-31. My question is what is considered as high frequency for that manner?

In my case, one of these IO's (P0.26) is used as a CS (for SPI communication) and is being toggled at ~4KHz. Consequently, there is no radio activity (i.e if I toggle P0.25 instead, then no problem).

By the way I'm using the WLCSP version on a custom bourd, but on the development kit (QFN package) I see no such problems.

[run_ar]

I think it's best to avoid using those pins on the WLCSP while the radio is active. Consider using radio notifications to avoid that.

[liron]

Thanks. For sure in my future designs I will avoid using them, but in the meanwhile, how would you suggest using the radio notifications? by making sure not to toggle these IO's during radio?

[run_ar]

Yes, These pins are very close to the radio, so toggling the pins could affect radio modulation. You can use radio notifications to avoid toggling it during radio activity, but if you have a lot of SPI communication it would be better to use another pin for that.