ESP32 Forum

Another question - I added led to my board to pin no 11.
I uploaded sketch, and I barely see led light instead of bright flashes - When I measured voltage on gpio11 - it shows 1.57V.

So what's wrong with using: in blink example?

Hi zhivtko,

GPIO 11 is used as the SPI flash CS line by default (pin name SD_CMD), so it's not a good choice for general purpose I/O. I think the dim light & low voltage you're seeing is caused by the high duty cycle on this pin as it's being used to load code from SPI flash.

Consult the ESP32 pin list document (available from the reference documents section for a list of pins, or you can consult the WROOM32 schematic. The pins named SD_xxx (under Pin Name heding, GPIO 6-11 inclusive) are used for SPI flash so are best left unconnected otherwise.

Angus

Oh that's a shame - I just followed pinout picture and pin11 is indeed shared for flash and gpio...
But if gpio could not be used - why put it on this image?
https://www.google.si/url?sa=i&rct=j&q= ... 2399122428

As I am concerned my post is solved.

Why they mark GPIO11 when it is flash reserved? Ughh...
So basically all this SD_ pins fall under same flash operation pins that user could not use since then flash would be useless?

This is correct, unfortuntely. It is possible to use these pins to share other devices on the SPI bus of the SPI flash if you're very careful (use a separate CS line, only talk to the other SPI device(s) while the SPI flash cache mapping is disabled). But in general it's best to not use them.

The diagram you linked was not created by Espressif, but I've emailed the author with a couple of suggestions about extra labels.

This is correct, unfortuntely. It is possible to use these pins to share other devices on the SPI bus of the SPI flash if you're very careful (use a separate CS line, only talk to the other SPI device(s) while the SPI flash cache mapping is disabled). But in general it's best to not use them.

The diagram you linked was not created by Espressif, but I've emailed the author with a couple of suggestions about extra labels.

Would really like to use these for sdcard limited r/w operations. Possible with separate cmd lines? Or maybe SD card cmds are mutually exclusive with flash commands?