external RAM for arduino?

Forum 2005-2010 (read only) Hardware Interfacing
1

Does anyone have suggestions for easy/simple/cheap (yeah, pick one or two) RAM solutions for the Arduino? I'm not talking about flash, EEPROM, or FRAM which all have a limited number of write cycles and are slow. I need several kB.

I'd like to have a serial (preferably SPI) interface so as not to occupy too many pins. I could probably use a couple of shift registers and connect a parallel RAM of some flavor, but I would like to keep the component count low.

I've done a bit of googling with no luck. Any suggestions?

-j

2

not sure if the chip is comparable, but these guys are using 32K external ram on an Atmeaga 128...
http://www.ethernut.de/

3

Thanks, but this is standard parallel memory; that 32k SRAM takes 16 lines for addressing, 8 for data, and 3 more for control, which uses roughly 100% of available I/O on the arduino.

I guess I could make my own "SPI SRAM" by using a dedicated ATmega8 in SPI slave mode and a typical SRAM, but I'm hoping for something a bit simpler.

thanks,
-j

4

Have a look at ELM - Cheap DSP Experiments
First check if the component is still available.

I hope this will help

Nicolas

5

Not that I could give any advice on how to make it work, but in browsing Jameco's catalog I see EEPROM and FLASH memory in serial versions. For example, the ST Serial flash memory I am looking @ is 20MHz, 3V, SPI bus for <$2.00 (#659913).

I would like very much to be able to hook up extra memory to the serial pins too.

6

There's a tutprial on using an SPI interfaced flash chip - see http://www.arduino.cc/en/Tutorial/SPIEEPROM .

Flash and EEPROM are slower than RAM but, more importantly, they have a fixed number of write cycles before they fail.

-j