ESP32 Forum

Mod note: This topic has been split off from viewtopic.php?f=10&t=6912

Thanks for info. I thought ive been reading some time ago that esp32 can support only 4MB of ram, but still its very good module, especially version with 128Mb of flash and is worth to mention its available now.

Ah, sure, and the upper 4MiB can still be useful for people implementing big ringbuffers; just thought I'd mention this before people get ideas of happily doing malloc(7*1024*1024) in their minds.

ESP_Sprite wrote:Ah, sure, and the upper 4MiB can still be useful for people implementing big ringbuffers; just thought I'd mention this before people get ideas of happily doing malloc(7*1024*1024) in their minds.

As this is the official Espressif module, it would be good to provide the (official) example of using the upper 4MB part of the SPIRAM.
How exactly can we "implement a big ringbuffer" in the upper 4MB.

One way could be to reduce the amount of spiram heap and use the free mmu pages as windowed access to the rest of the ram with your own read/write functions.

Should this topic be in News?

Yes, that's going to be supported by esp-idf. And no, this discussion shouldn't be in news; if people want to ask or say more, I'll split those things off to a new topic.

WiFive wrote:One way could be to reduce the amount of spiram heap and use the free mmu pages as windowed access to the rest of the ram with your own read/write functions.

Should this topic be in News?

There are several ways how this could be accomplished, but none is documented by Espressif, neither esp-idf has any means to do it.
My point was, if Espressif released the module with 8MB of SPIRAM, there should be some support for it in esp-idf, and some documentation how to use it.

The topic should probably be moved to hardware.

Edit:

ESP_Sprite wrote:Yes, that's going to be supported by esp-idf. And no, this discussion shouldn't be in news; if people want to ask or say more, I'll split those things off to a new topic.

Thanks.

In that case i have question about possible usage of extra 4mb of psram. This is what i can think of:

• use ram to shadow application from flash for example if app requires a lot read/write operations to decrease wearing of flash;
• i remember there was a question if its possible to load/download app to ram and execute from there; i can imagine home/industrial applications with power grid and battery backup that can be used this way
• is it possible to have 2 separate memory banks (4mb each), one for each cpu core?

Hi, I am using an ESP-Wrover-Kit which has a ESP-Wrover module installed in it. It features a 4 MB external SPI flash and an additional 8 MB PSRAM. In the datasheet, it is mentioned that up to 4 MB of PSRAM can be mapped into CPU data memory space at a time. As only 4 MB memory space is considered for External SRAM (0x3F80_0000 to 0x3FBF_FFFF), how can I use (map) the extra 4MB? What would be the CPU data memory address to map that extra 4MB? Thanks!

There will be an option to use part of the 4MiB mappable address range to bank-switch the remaining memory in. Afaik it hasn't made it into esp-idf yet, though.

ESP_Sprite wrote:There will be an option to use part of the 4MiB mappable address range to bank-switch the remaining memory in. Afaik it hasn't made it into esp-idf yet, though.

Bad ESP_Sprite, bad bad bad , we have this API and you didnt tell us about it

I think we have new field to discover and few people will get hands dirty with it:
https://docs.espressif.com/projects/esp ... himem.html

Have a fun