What are the consequences of using low-frequency GPIO lines with a high-frequency signal?

RE: What are the consequences of using low-frequency GPIO lines with a high-frequency signal?

havingnordicfun — Fri, 27 Mar 2020 20:32:24 GMT

Hi Andreas, just wanted to confirm what sort of modulation index you're referring to. Can you elaborate?

RE: What are the consequences of using low-frequency GPIO lines with a high-frequency signal?

Andreas — Thu, 26 Mar 2020 08:08:29 GMT

Hi,

No I probably just mixed up counter and timer when issuing my response to you, sorry about that. Using the HF crystal as source for the HFCLK will give a stable CPU clock, every sample should happen as accurately as possible. I do not believe have investigated whether there can be differences between the pins, the note in the PS only refers to degratation or radio performance parametres.

Best regards,

Andreas

RE: What are the consequences of using low-frequency GPIO lines with a high-frequency signal?

havingnordicfun — Wed, 25 Mar 2020 17:31:29 GMT

Hi,

Are you referring to a hardware timer going unaffected? To be sure, I'm asking about the ability to properly sense every change of the 3Mhz GPIO line in software alone, without GPIOTE or PPI or a timer tied to the HF crystal.

Thank you!

RE: What are the consequences of using low-frequency GPIO lines with a high-frequency signal?

Andreas — Wed, 25 Mar 2020 09:34:43 GMT

Hi,

Not exactly, the timer accuracy should not be affected, at least if using the HF crystal as clock source. RX sensitivity and modulation index are radio 'performance parametres', you might see degraded radio performance while the pin is being toggled.

Best regards,

Andreas

RE: What are the consequences of using low-frequency GPIO lines with a high-frequency signal?

havingnordicfun — Tue, 24 Mar 2020 14:47:29 GMT

Thank you for the reply. So would it be fair to say that the counter in the example above may not align properly in every case and miss cycles in the external clock due to decreased sensitivity?

RE: What are the consequences of using low-frequency GPIO lines with a high-frequency signal?

Andreas — Tue, 24 Mar 2020 11:12:40 GMT

Hi,

Expected consequences are degraded RX sensitivity and possibly modulation index.

Best regards,

Andreas