Questions about i/o pins

[Leef_me]

I wanted to use the ESP32-Gateway board for WIFI, Ethernet, Uart-serial and I2C.

I was just reviewing the signals in the I/O pin header for ESP32-Gateway.
I have (2) rev E boards.
Reviewing the published PDF schematics of these boards, some of the I/O pins
have a Usage note:

    GPIO6 TO GPIO11- DEBUG ONLY!
    USED FOR INTERNAL FLASH MEMORY!

Does this mean for Rev E, I'm limited to using the signals
            GPIO16,17,32,33,34,35,36,39?

Can you explain why GPIO34,35,36,39 are input only?

[LubOlimex]

The revision doesn't matter, GPIO6 to GPIO11 are always used for the internal flash memory if the board has ESP32-WROOM-32 module. Maybe we should have simply left those pins unrouted since they cause a lot of confusion.

You can read about these pins in the ESP32-WROOM-32 documentation here:

https://www.espressif.com/sites/default/files/documentation/esp32-wroom-32_datasheet_en.pdf

Page 4 notice:

* Pins SCK/CLK, SDO/SD0, SDI/SD1, SHD/SD2, SWP/SD3 and SCS/CMD, namely, GPIO6 to GPIO11 are connected to the integrated SPI flash integrated on the module and are not recommended for other uses

> Can you explain why GPIO34,35,36,39 are input only?

It is not related to Olimex design, the ESP32 creators espressif made the chip that way. Refer to the same document and the table on page 3 and check "Type" column - it indicates if a pin can be input, output, both, or if it is related to the power circuit. You see pins IO34 and IO35 - they are type "I", which means only inputs.