ESP32 Forum

Hi,

I'm working on a project using of only ESP32-S3FN8 chip. The Chip hasn't external flash memory.

-I want to use Pin32~Pin35 (SPICS0,SPICLK,SPIQ,SPID) pins as GPIO but I didn't it. This way not recommended on documents but I need to use it like this.

-I tried change pin function for each pins via gpio_hal_iomux_func_sel(PERIPHS_IO_MUX_SPIQ_U, FUNC_SPIQ_GPIO31). MCU is continuously resetting When I load the code. Not working.

-I understand that MCU supposing have an external flash and It wanted use it. If this is true, How can I disable "External flash mode" and switch to "Internal flash mode". If this is not true, What can I do for using theese pins as GPIO ?

The internal flash is connected to the same pins. That is why we strongly do not recommend using it, and that is why your ESP crashes when you try to connect to those pins.

Firstly, thanks your reply.

Does the same apply to using the SPI feature ? If the internal flash and external flash are connected to the same pins and there isn't any external flash on my system, Not recommended use GPIO and SPI mode theese pins Is it true ?

- Should I use theese pins only when there is an external flash on my system? Otherwise, I shouldn't use these pins. Is is true ?

An addition. I want to use Shift Register or Sensor on these pins. Can I use these pins in SPI Mode for read Shift Register or Sensor.

If you look at section 2.6 'Pin-to-Pin Mapping Between Chip and In-Package Flash/PSRAM', it defines which pins you can't use for your specific ESP32-S3. For the S3FN8, your image is indeed correct.

In theory, you could use other SPI devices on this port as well, but at this particular point in time, no driver supports it, and we're unsure if we'll ever add it into our driver as it comes with a bunch of complications. So in practice: no, you should leave these pins N/C.

thanks @ESP_Sprite it was very helpful.