nRF52 GPIO near radio

[jcondon]

Greetings. Could you provide more information on the issues with GPIO located near the radio in the nRF52 (PS 18.2.1)? Specifically, what is considered "high frequency digital I/O with large sink/source current." Are situations that are high frequency and low current fine? At what point should we start worrying?

For example, would an 8MHz SPI clock cause an issue? What about a 1kHz 5mA pulse?

[Susheel Nuguru]

Not remember exactly but I think GPIO 18 and 19 are really close the the radio module. And 8MHz clock is harmonics of 16MHz system clock that radio uses and this could cause relatively more noise. If you choose some other pins and/or choose different SPI clock frequency which are not the harmonics of radio clock, then you should not have anything to worry about.

[jcondon]

According to the Product Specification (18.2.1), pins 27-29 and 37-43 are all considered affect the radio with high frequency IO & large sink/source current.

As far as I'm aware, the only available SPI clock frequencies are all harmonics of the system clock because there is only a single clock divider (vs pre/post divisions). Is there another SPI register I'm missing or somewhere else to adjust the peripheral clock speed?