ESP32 Forum

So GPIO 34-39 and input only. Internal flash 7-10 are unavailable (yet exposed on the board). Are there any other differences or limitations of other GPIO pins? Like for one wire or CS for SPI devices?

riklaunim wrote:Are there any other differences or limitations of other GPIO pins?

Hi riklaunim,

A good top level overview is provided in section "Peripherals and I/O" of https://learn.sparkfun.com/tutorials/es ... okup-guide.

This is the general functionality overview. What I have problem with is some odd behavior of some GPIO. Like one-wire with neopixel LEDs - some GPIO "just work" while other sometimes also give some interference. Adafruit OLED aside of SPI uses two IO pins extra and like GPIO 26, 27 did not work correctly while 32 or 4 did. It may be specific to the PCB design but still makes me wonder if every GPIO is equal in terms of basic digital I/O functionality.

The low level details for all the pins / pin groups are covered in "Appendix A" of the ESP32 Datasheet.

In your case I would check:
1. A.1. Notes on ESP32 Pin Lists
2. A.4. IO_MUX"

Seeing different behavior between seemingly identical pins (according to the datasheet), I would first check the board design and verify how internal pull up / pull down is configured after reset and If the application code is changing this configuration.