nrf52, clarification on Low Frequency I/O for input

[jgartrel]

I see that the PS for the nRF52 series shows that some pins (including all of the Analog pins) are recommended to be used as: "Standard drive, low frequency I/O only" pins, with "low frequency I/O" defined as "signals with a frequency up to 10 kHz" while using the radio due to the proximity of the pins to the radio.

1. Does this restriction only apply to applications that drive the pins (i.e. GPIO output, toggling the pin at frequencies greater than 10kHz)? What about using the SAADC to read signals greater than 10kHz; will that negatively impact the radio performance?
2. Similarly, what about using the pin as GPIO Input with pull-up resistor engaged while monitoring port events with an external source driving the pin at frequencies greater than 10kHz; will that degrade radio performance?
3. What about question #2 without monitoring port events for that pin?

Any clarification you can bring to this question would be greatly appreciated.

Thanks in advance,

James

[Simonr]

Hi James

1. This restriction is only related to radio performance. The pins that have this "recommended usage" tag will likely affect the radio if running at frequencies higher than 10kHz and/or in high drive modes. Both reading and writing signals above 10kHz may affect radio performance I'm afraid.

2/3. I'm afraid all operations on these GPIOs above 10kHz may affect the radio negatively if run simultaneously as the radio. It should be fine however, if the GPIOs and the radio are not run simultaneously. 

Note that Analog inputs AIN2 and AIN3 do not have this restriction, and can be run at higher frequencies without affecting the radio, as these are located physically further away from the radio.

Best regards,

Simon

[jgartrel]

Thank you so much for the clarification.