[sdiy] external memory for microcontrollers

[Eric Brombaugh]

I've used the STM32 FSMC/FMC with both PSRAM and SDRAM up to 64MB which 
is probably sufficient for the 5 minute buffer lengths you mentioned. 
It's easy to set up and works without too much fuss. You'll generally 
find that you have to move to the 144-pin package to get sufficient pins 
for a memory connection though, and that will increase the cost of the 
MCU somewhat.

Large SRAM is fairly expensive, PSRAM (self-refreshing DRAM) is getting 
hard to find in non-BGA packages. SDRAM is very cheap and readily 
available but requires you to get an MCU that knows how to drive it - in 
the STM32 that means only some of the newer F4 and F7 parts which have 
the FMC interface.

Eric

On 02/15/2017 03:41 PM, Chris McDowell wrote:
> Howdy list,
>
> I've been thinking about delays, reverbs, and loopers a bit lately, and wondering what the best way to add more memory to a microcontroller.
>
> I've been using STM32, especially the F3 series that tops out around 32k. The part I'm really digging on (STM32F334) has 12k only. I've played with the 23LC1024 SPI SRAM chips, and it seems like they're fast enough with dual or quad SPI (and maybe just barely fast enough with regular SPI @ 18Mbits/sec). They cost about as much as the micro itself, though, which isn't quite cool, and I'd really need a few. I know some of the ST parts have the "FSMC" memory controller for SDRAM etc, and maybe that's the way to go here. not worried about the storage being non-volatile, I just want more ram to play with. I'm seeing some ~$50 looper pedals from not-too-huge manufacturers with over 5 minutes of time, so I figure this must be reasonably affordable.
>
> anyone have better ideas or experience here?