According to the ESP32 Hardware Design Guidelines, a 0.1uF cap should be added to the SENSOR_VP and SENSOR_VN pads when using them as an ADC. Why is it then that the subcircuit schematics shown in the document don't include it? The Sparkfun ESP32 Thing schematic also doesn't include the 0.1uF cap in their design.

Another curiosity, why does it show these pins as part of the RF matching circuit? Can we not use the SENSOR_VP and SENSOR_VN pins for ADC if they're part of the RF matching? And in what way do they contribute to the RF functionality?

ADC Instructions RF Subcircuit

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    \$\begingroup\$ It's not part of the RF matching, it's just drawn near it and someone excepted that area of the schematic without bothering to painstakingly erase it. \$\endgroup\$ – Chris Stratton Jan 3 at 5:07
  • \$\begingroup\$ Thanks @ChrisStratton, that answers my secondary questions. More urgently though, what does the NC stand for (no connect?) and why are there 270pF capacitors instead of the 0.1uF cap? \$\endgroup\$ – YNGVV Jan 6 at 20:54
  • \$\begingroup\$ You shouldn't really ask brand new questions in a comment: there are no doubt existing questions here on the meaning of "NC". As for the particular capacitor chosen for the sensor in this drawing, you'd have to ask the designer. But a drawing presented for the purposes of illustrating the RF circuitry is probably not a good reference for that - it might be stale, having been drafted before the chip was characterized for example and may not reflect the most developed wisdom on the sensor. It's not hard to find 0.1uF and 270 pF caps in the same package, you can try both and compare results. \$\endgroup\$ – Chris Stratton Jan 6 at 20:58

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