How do I use esp32 as an external RAM for other microcontroller?

[Mr-Techtron]

This might sounds quite stupid but I was wondering if esp32 can be used as an external RAM for other micro-controllers? Please, can someone shed some light on this topic, is there any way that I could achieve this? Thank you.

[Sprite]

That depends, what RAM interface does the other microcontroller have? In general, what are you trying to do, what problem are you trying to solve?

[Mr-Techtron]

Thank you @ESP_Sprite for your response, this is just a general question as a hobby project if this could be achieved. I'm thinking of using SPI if that is not possible could it be possible with FSMC of stm32f407?

[Sprite]

If you're thinking of using something with an SPI interface and code you can presumably control yourself, why not put a dedicated RAM chip (like an ESP-PSRAM64H or so) there instead of trying to abuse an ESP32?

[Mr-Techtron]

Yes, you're absolutely right but I want to use the wifi/ethernet/BlueTooth capability of esp32 too as a communication interface. If I could use it as an external RAM, it would be an icing on the cake. I just want to know if this could be achieved and to what extent. With this, I can extend the capability of our older boards we've without having to change the hardware design.

[Sprite]

Well, you have a whole heap of external interfaces (SDIO, UART, I2C, SPI, ...) you can use to communicate with the ESP32; as long as you write the software and the other side knows what protocol to speak, there's nothing stopping you from implementing a communication protocol that also allows you to save a few bytes on the ESP32.

[Mr-Techtron]

Thank your for your concern. I think I've to do some more digging myself then.