ESP32 Forum

First time here and somewhat new to ESP32, especially S3. I recently designed a board and used the ESP32-S3 as the MCU. The problem is when I created the BOM the wrong part number got used and I have prototype boards with the ESP32-S3-WROOM-1-N16R2 instead (contains onboard PSRAM). This is causing problems when we try to use GPIO 35, 36 & 37.

Before creating a new PCB (to use the correct S3), is there a quick way to disable the onboard PSRAM in the R2? The sad news is we are using the Arduino framework in PIO, so it seems access to some of these bits is tougher ... unless there's a way to set the PSRAM state to disabled that persists across power cycles.

Any thoughts?

If I read it correctly, it shouldn't be an issue and the pins should be available. Per the datasheet of that module, those pins are occupied if the module has OSPI (=octal) PSRAM; per the same datasheet the -N16R2 uses quad PSRAM and flash. (If you used an -N16R8, you would have an issue, as that module *does* use octal PSRAM).

Sorry, my mistake; it is the R8 variant. So the original question still remains - is there a way to disable the internal PSRAM so we can test the proto boards we currently have?

I think you can if PIO/Arduino allows you to ignore the PSRAM. In that case, you can configure the PSRAM CS (SPICS1, GPIO26) pin as a GPIO and make it always high; that should allow you to use the remaining pins freely.

Thank you for the help here!

After instrumenting the code to show the amount of PSRAM and coaxing PlatformIO to build without support for PSRAM, it now works fine. There was also a problem with getting the right pins to be configured for SDA & SCL. A logic probe cleared that up.

This is the problem with pre-packaged libraries and code; sometimes it's not clear who is doing what! We ended up creating a board variant and defining the board so now we control all the defaults/assumptions.

Thanks for your help!!

Hi @meisner

I am having the same issue. trying to get pins 36 and 37 to work with I2C. Could you please explain a bit more about how you solved this problem.
How do you disable that feature to free up the pins? I am using Arduino code to flash.

Thanks