ESP32-U4WDH PSRAM: wiring, which chips, how to use ?

[vhaudiquet]

Hello,

The official espressif FAQ on hardware says:

The ESP32-U4WDH chip supports external PSRAM chips. However, only the ESP-PSRAMXXH chip released by Espressif is supported. Third-party PSRAM chips are not supported.
For hardware design, all the PSRAM pins except for the CS pin can be multiplexed with Flash. For more information, please refer to the ESP32 Hardware Design Guidelines.
Also, when designing the PCB, please make sure that the GND of the PSRAM to the GND of the ESP32-U4WDH is as short as possible; Otherwise, the signal quality may be affected.

(cf. https://docs.espressif.com/projects/esp ... sram-chips)

I'm struggling to understand multiple points:
- I could not find any of those ESP-PSRAM chips, but I found LY68L6400 chips which are supported by esp-idf. Given idf support, shouldn't those work as well ? I don't see how the hardware could be limited to specific QSPI chips if there is software support behind
- The flash mapping are as follow:

Capture d’écran du 2025-06-03 22-29-41.png (28.65 KiB) Viewed 126 times

Should I just connect the PSRAM the same way ? Maybe change CS pin to another GPIO ? Which one then ? Any GPIO would do ? Or just GPIO17 maybe ? I'm kind of lost.

Would this be the right way to wire the PSRAM ?

Capture d’écran du 2025-06-03 22-31-11.png (87.08 KiB) Viewed 126 times

I already ordered PCBs wired this way, and esp-idf does not detect the PSRAM. Can I fix it, with this specific chip ?
I tried re-wiring CS (CE#) to GPIO0 and changing configuration, but it did not work either.
Is there a way for me to use that ? Even by manually connecting to the PSRAM ?
Or is it doomed and should I re-design differently ?

EDIT: More specifically, with CS wired to the same as the flash, it triggers a reboot (boot loop) ; I guess its trying to select the flash and the PSRAM at the same time which obviously does not work. However, when connected to pin 0, it gives me "id 0xffffffff" not recognized, or something like that, which must means that it is only reading ones on the line, and I'm not exactly sure why.....

Thank you !