Pin Classification and Function Summary

flux

1:04

Considering file usage.

Deciding on citations.

Considering input types.

Espressif encountered an error.

From the datasheet and Espressif pin notes for this module, here are the pin groups you asked for:

Bootstrap / strapping pins

These are sampled at reset, then can act as normal IO afterward:

IO0 / GPIO0 — pin 3
- Boot mode strap
- Default internal pull-up
IO45 / GPIO45 — pin 39
- VDD_SPI voltage strap
- Default internal pull-down
IO46 / GPIO46 — pin 40
- Boot mode strap
- ROM message printing strap
- Default internal pull-down

Boot-mode detail:

SPI boot: GPIO0 = 1, GPIO46 = any
Download boot: GPIO0 = 0, GPIO46 = 0
Avoid: GPIO0 = 0, GPIO46 = 1

Input-only pins GPIO input-only

IO46 / GPIO46 — pin 40
- Explicitly listed as input only

Dedicated input pin

EN — pin 41
- Chip enable input
- Not a general-purpose GPIO
- Must not be left floating

Pins connected to internal memory

These are the exposed module pins tied to the internal flash/PSRAM interface, so they should be treated as reserved rather than general-purpose IO:

IO26 / GPIO26 — pin 25
- Connected to PSRAM CS
- Datasheet says it cannot be used for other functions
IO33 / GPIO33 — pin 27
- Memory interface signal
IO34 / GPIO34 — pin 28
- Memory interface signal
IO35 / GPIO35 — pin 29
- Memory interface signal
IO36 / GPIO36 — pin 30
- Memory interface signal
IO37 / GPIO37 — pin 31
- Memory interface signal
IO38 / GPIO38 — pin 32
- Memory interface signal

Practical takeaway:

Definitely reserved: IO26
Also normally reserved / use with caution: IO33 to IO38
Espressif also notes the SPI0/1 memory bus pins are usually not recommended for other use.

USB pins

Yes, USB is present:

IO19 / GPIO19 — pin 22 — USB_D-
IO20 / GPIO20 — pin 23 — USB_D+

If you want, I can turn this into a pin classification table for the whole module next, including:

power pins
ground pins
strap pins
reserved memory pins
USB/UART/JTAG pins
safe general-purpose IO pins

Use attached datasheet

Add exact part number

Include pin numbers

a day

Reviews

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