AVR parasitic pin capacitance < 10pF

[ralphd]

Not satisfied with the 10pF rule-of-thumb, I decided to measure the parasitic capacitance for AVR IO pins.  While 10pF may be a reasonable number for a chip and a trace a couple cm long, the capacitance of a floating pin with no trace is as low as 6pF.  Even with an attached trace and header, and plugged into a breadboard, parasitic capacitance is as low as 7pF with a QFN-32 ATmega328p.

http://nerdralph.blogspot.ca/2015/10/parasitic-capacitance-of-avr-mcu-pins.html