On page 3 of the esp32-wroom datasheet (PDF) it shows a series of pins with type "I".

What does pin type I mean? Are these different to the pin type I/O pins? If so, how?

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    \$\begingroup\$ It's Input. \$\endgroup\$ – Eugene Sh. Feb 27 '18 at 22:15
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    \$\begingroup\$ @RenegadeAndy, what does I/O mean? \$\endgroup\$ – jsotola Feb 27 '18 at 22:16
  • \$\begingroup\$ @jsotola Hm... One/Zero?? :) \$\endgroup\$ – Eugene Sh. Feb 27 '18 at 22:18
  • \$\begingroup\$ @EugeneSh. So, undefined or infinity (if you are taking the limit)? \$\endgroup\$ – Samuel Feb 27 '18 at 22:23

Some pins can be input and output: I/O (or sometimes General Purpose I/O: GPIO).

Some pins can be outputs only: O.

Some pins can be inputs only: I.

Some pins can be power: P (note that some datasheets will differentiate between input power and ground).

And some pins can be not connected: NC.

  • \$\begingroup\$ There is a P type as well. For Power.. \$\endgroup\$ – Eugene Sh. Feb 27 '18 at 22:23
  • \$\begingroup\$ @EugeneSh. I didn't actually look at the datasheet... I know, for shame. \$\endgroup\$ – Samuel Feb 27 '18 at 22:26
  • \$\begingroup\$ Sorry Samuel but I/O is a pin direction type, whereas GPIO is a pin label prefix used by microcontrollers. So they've distinctly different meanings and are not alternative names for the same thing. GPIO1 is the name of pin of type I/O, same as D7 is a pin of type I/O. \$\endgroup\$ – TonyM Feb 27 '18 at 22:47
  • \$\begingroup\$ @TonyM No need to be sorry, they're not as mutually exclusive as you seem to imply with "distinctly different meanings". Both are of the direction category which is input/output, so yes, in some cases they are in fact the same thing. All squares are rectangles, but not all rectangles are squares. All GPIOs are I/Os, but not all I/Os are GPIOs. \$\endgroup\$ – Samuel Feb 27 '18 at 22:52
  • \$\begingroup\$ Oh, I wasn't implying a point with "distinctly different meanings", I was firmly stating it. GPIO is a pin function and label for microcontrollers but it's not a direction. The General Purpose part describes a pin that a microcontroller's CPU can read or write. Logic chips, memories, FPGAs etc don't have GPIO pins, they have I/O pins. Important not to confuse the two, one's a noun and one's an adjective. \$\endgroup\$ – TonyM Feb 27 '18 at 23:17

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