SPI RAM - Support for other chips

[caseymdk]

Hi all,

I love the fact that the ESP32 supports SPI RAM. I understand that there are limitations to putting a lot of RAM on-die, so I appreciate the option of being able to implement external RAM.

However, I was surprised to see that the only chip that's supported is the PSRAM chip manufactured by Espressif. There are a lot of SPI RAM chips available on Digikey that only use a slightly different instruction set. Is it difficult to modify the code to support these chips?

I looked at the "PSRAM.c" code, but it's a bit over my head, and I suspect there may be some hardware functionality that's going on that I can't see...(the file looks too small to implement all functionality). So I'm wondering, what's the limiting factor to supporting other types of external SPI SRAM chips?

Thanks!

Casey

[loboris]

Hi all,

I love the fact that the ESP32 supports SPI RAM. I understand that there are limitations to putting a lot of RAM on-die, so I appreciate the option of being able to implement external RAM.

However, I was surprised to see that the only chip that's supported is the PSRAM chip manufactured by Espressif. There are a lot of SPI RAM chips available on Digikey that only use a slightly different instruction set. Is it difficult to modify the code to support these chips?

I looked at the "PSRAM.c" code, but it's a bit over my head, and I suspect there may be some hardware functionality that's going on that I can't see...(the file looks too small to implement all functionality). So I'm wondering, what's the limiting factor to supporting other types of external SPI SRAM chips?

Thanks!

Casey

I couldn't find any SPI RAM chip available on DigiKey, could you give a link to any.

Except Espressif SPIRAM, Lyontek's psRAM chips also works with ESP32.
I have also tested IPUS IPS6404 SPIRAM (the 3.3V version available at Electrodragon and it works without issues.

[WiFive]

https://www.digikey.com/en/product-high ... am-devices?

But $2/mbit vs $0.10/mbit

[loboris]

https://www.digikey.com/en/product-high ... am-devices?

But $2/mbit vs $0.10/mbit

And max size 128 KB + max clock 20 MHz, quite unusable as ESP32 external RAM.

[caseymdk]

And max size 128 KB + max clock 20 MHz, quite unusable as ESP32 external RAM.

Yes, but even more unusable is the lack of the ESP-PSRAM chip from distributors...I would much rather use a different, 128KB chip than nothing.

Is the 20MHz a deal-breaker? Looks like the ESP32 runs external RAM at 40MHz by default...could this be decreased to 20MHz?

[WiFive]

Yes, but even more unusable is the lack of the ESP-PSRAM chip from distributors.

Did you try to buy direct from espressif?

[caseymdk]

I have not, I'm not at a point where I can buy large volumes, which I assume I'd need to in order to get it direct.

[WiFive]

Usually the first 2 sample orders have no volume requirements. Especially if the part is not available through distribution I think they will be more accommodating.

[mrbhou]

Except Espressif SPIRAM, Lyontek's psRAM chips also works with ESP32.
I have also tested IPUS IPS6404 SPIRAM (the 3.3V version available at Electrodragon and it works without issues.

Hi loboris,
I also add more Rams for ESP32 Wroom 32D by using IPUS IPS6404, what you recommend.
But it doesn't work.
Do you have to modify anything in code ?
Of cousre, I connect it following reference design of ESp32 Wrover, which has 4Mb Psram External.
Can you help me?
Thanks.

[loboris]

Hi loboris,
I also add more Rams for ESP32 Wroom 32D by using IPUS IPS6404, what you recommend.
But it doesn't work.
Do you have to modify anything in code ?
Of cousre, I connect it following reference design of ESp32 Wrover, which has 4Mb Psram External.
Can you help me?
Thanks.

You just have to connect SPI-RAM chip to the right pins and use one 10K pull-up on CS pin.
You can check my post here.