Has someone succeeded extending RAM on the nRF53 series?

[cstches]

Hi, although there are many guides and stories about attaching the nordic to external storage NVM, there aren't infos about doing the same with RAM. 

I even found some threads recommending usage of cheaper SD-Cards, but this is crazy. I am talking about RAM here.  I understand NVMs can be misused for this, but this can not be considered for serious work, considering wearing out.  I am sure there are competitors offering chips able to extend their ram with SPI compatible PSRAM but I don't get why it may not be possible to achieve this with nordic chips. Any suggestions?

[AMarch01]

You don't supply many details, but I have had some success with Everspin products. They don't have great $/bit but they have virtually unlimited read/write capability. 
A M

[Kenneth]

Hello,

It's not supported by design to extend the RAM, I would think main reason is that it would be very inefficient without some very large cache and high speed interface, because if the CPU need to use a variable you would end up to use very many clock cycles to fetch any data through an external QSPI interface.

I guess you can still use external memory if you just need a way to store, update and read external memory, but you will need to make the application manually use the serial interface to do this.

Kenneth

[AMarch01]

It would be fun to see an "nrf57" with M7 and external SRAM interface, but I can't think of use case for such a monster... unless Bluetooth in the 6Ghz range can bring about some need.

[cstches]

Well, I tried to remain as much abstract as possible to focus directly on how to expand memory instead of challenging the reasons, why much memory might be needed in the first place. But anyway to give more context, I may want to control a BlueTooth MESH network of sensors/actuators from a system outside the MESH world.  Lets say I need kind of a HUB/Gateway able to do provisioning, configuring of the network. Outside MESH I would for example connect to the HUB via Ethernet/WiFi/UART or whatever other technology the HUB may translate into.  Then I could retrieve information from the network or send commands via the HUB, or tell the HUB to reconfigure the network, etc.   Therefore the HUB may need to keep some data during runtime from all the Nodes of this network. Based on this I don't know if internal Memory may be sufficient to manage a network of hundreds, dozens or just a few Nodes.  This is the place where I know that the Chip may have sufficient power to process all the information, but the limitation would be memory.  I want to avoid having to get a much more powerful chip with either more internal memory, or with expansion possibilities.    Perhaps the nRF53 is not intended to support "centralized" applications and encourage the "decentralized" approach intrinsic to the nature of e.g. MESH.  So the CHIP may be fine for individual sensors/actuators but definitely not for a HUB. Other opinions?

[AMarch01]

The reason I asked about details, is that I wasn't sure how quickly you wanted to the data in this memory to be available or perhaps if you wanted to execute from it or something. 

I gathered from your consideration of an SD drive, that you just need extended storage, but you didn't want to worry about wear.
For that I would look at SPI serial MRAM or FRAM products, they have the bonus of retaining data on power off, but for your needs a near limitless r/w wear count. 

What they don't give you, is a lot of extra storage, but anything you put in these would save your processor space, in exchange for waiting for the spi controller to read your records from the device.

A. M.

An example you could test with 
Adafruit SPI Non-Volatile FRAM Breakout - 2 Mbit / 256 KBytes [MB85RS2MTA] : ID 4718 : Adafruit Industries, Unique & fun DIY electronics and kits

These guys might be able to give you a board to test with.
Evaluation Board - Serial Peripheral Interface (SPI) MRAM Products | Everspin