Pin Classification Overview

Worked for 1 min 41 sec

I checked the Espressif datasheet for this module. Here are the pin groups you asked for:

Bootstrap / strapping pins

These pins are sampled at reset, then can be used as normal GPIO afterward.

Table

Module pin	Pin name	Reset role	Default strap
16	IO46	Boot mode select with IO0, ROM message printing control	Weak pull-down
26	IO45	VDD_SPI voltage select	Weak pull-down
27	IO0	Boot mode select with IO46	Weak pull-up

Boot notes

Table

IO0	IO46	Result
1	any	SPI boot
0	0	Joint download boot
0	1	Invalid combination, avoid

Input-only pins

Table

Module pin	Pin name	Notes
16	IO46	Input-only pin, fixed pull-down, also a strapping pin

That is the only input-only GPIO called out here.

Pins connected to internal memory / reserved by flash interface

These are the ones you should treat as memory-related or restricted.

Strongly reserved / not recommended for other use

These correspond to the SPI0/1 interface used for in-package flash, or recommended for flash/PSRAM connection.

Table

Chip GPIO	Module pin exposure	Module pin name
GPIO26	not exposed as GPIO26 label on module	not broken out directly
GPIO27	not exposed as GPIO27 label on module	not broken out directly
GPIO28	not exposed as GPIO28 label on module	not broken out directly
GPIO29	not exposed as GPIO29 label on module	not broken out directly
GPIO30	not exposed as GPIO30 label on module	not broken out directly
GPIO31	not exposed as GPIO31 label on module	not broken out directly
GPIO32	not exposed as GPIO32 label on module	not broken out directly

These are associated with higher SPI flash/PSRAM data lines or DQS, so use caution.

Table

Module pin	Pin name	Memory-related function in datasheet
24	IO33	SPIIO4 / FSPIHD
25	IO34	SPIIO5 / FSPICS0
28	IO35	SPIIO6 / FSPID
29	IO36	SPIIO7 / FSPICLK
30	IO37	SPIDQS / FSPIQ

Practical summary

Definitely memory-reserved / avoid: GPIO26 to GPIO32
Memory-related / use with caution: IO33 to IO37
Normal GPIO from your requested categories: the rest, except the special-case pins above

USB pins

Table

Module pin	Pin name	USB function
13	IO19	USB_D-
14	IO20	USB_D+

Short summary

Bootstrap pins: IO0, IO45, IO46
Input-only pins: IO46
Internal-memory / flash-related pins: GPIO26 to GPIO32 reserved, and IO33 to IO37 are memory-bus related / caution
USB pins: IO19 = USB_D-, IO20 = USB_D+

If you want, I can turn this into a pin classification table for all 41 pins next.

Use ESP32 datasheet

Flag restricted pins

Save pin notes

IO38

IO21

IO11

IO35

IO9

IO6

IO4

IO40

IO13

IO12

IO7

IO41

IO1

IO8

IO33

IO17

IO34

IO15

IO2

IO3

IO37

IO14

IO42

IO5

IO36

IO16

IO39

IO10

IO18

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