Clarification on what exactly is impacted by - "Standard drive, low frequency I/O only"

[Richard-CRT]

Hello all,

I've done a search and seen there are lots of questions related to this problem of what does "Standard drive, low frequency I/O only" actually mean. Several answers make reference to the concept of "radio performance", and how using these pins for GPIO faster than 10 kHz will degrade "radio performance". What is unclear is exactly what everyone means by "radio". It seems reasonable to assume they are talking about at least the multi-domain 2.4 GHz radio transceiver, but I want to clarify if there is any impact at all on the 13.56 MHz NFC interface, which is arguably also a "radio".

Thanks!

Richard

[ketiljo]

It's the receiver that will affected. High frequency IO with high drive will create noise on the power supply internally in the chip. This will affect the sensitivity of the receiver. If you look at where the pins with this note are placed, they are all on the same side as the radio.  The closer to the radio and the higher the frequency, the more will the sensitivity be affected. Less than 10 kHz is safe, no sensitivity degradation will ocure with any pin.

NFC is not affected.