Arduino Forum

Using Arduino => Storage => Topic started by: legoritmo on Oct 03, 2011, 06:30 pm

Title: Max capacity external memory RAM
Post by: legoritmo on Oct 03, 2011, 06:30 pm
Hi everyone! I am working in a project about realiable wireless communication, and I need a external memory for store data when the Arduino is out of range. So, my question is very simple. Does anybody know which is the bigger memory RAM that i can add to the arduino? Because the biggest that i found it was 23K256 (32KB), and this is too small. Thanks!
Title: Re: Max capacity external memory RAM
Post by: RuggedCircuits on Oct 03, 2011, 07:01 pm
How much memory do you need and how fast do you need to access it?

We have a MegaRAM shield (http://ruggedcircuits.com/html/megaram.html) for the Arduino Mega/Mega2560 that adds 128kilobytes of fast RAM. You can get more storage if you move to FLASH memory, or use a shield that has an SD card interface in which case megabytes or even gigabytes of RAM become accessible, but it is slower to write to these media.

Tell us more about your desired memory size and speed of access.

--
The Basic Motor Driver (http://ruggedcircuits.com/html/basic_motor_driver.html): simple, inexpensive motor driver for 1 stepper motor or 2 DC motors
Title: Re: Max capacity external memory RAM
Post by: pito on Oct 03, 2011, 10:43 pm
..You may try ramtron's FRAM FM25H20 (256kBytes, SPI 40MHz, 8pin smd). It works as a ram, and you get a bonus as it is nonvolatile.. Pito.
Title: Re: Max capacity external memory RAM
Post by: SH2011 on Nov 10, 2011, 10:44 am
There is a device IP12B512C serial SRAM with 64Kbyte available.
See www.ipsilog.com
Title: Re: Max capacity external memory RAM
Post by: Grumpy_Mike on Nov 10, 2011, 10:55 am
Quote
Does anybody know which is the bigger memory RAM that i can add to the arduino?

Yes in theory it is infinite, now how big do you need it to be?
Title: Re: Max capacity external memory RAM
Post by: relaxing on Nov 15, 2011, 04:22 pm

Quote
Does anybody know which is the bigger memory RAM that i can add to the arduino?

Yes in theory it is infinite, now how big do you need it to be?

1 megabyte.
4 megabytes would be even better.

I need low-latency read/write access to large amounts of memory for audio applications. It's a shame no one makes a board that supports this.
Title: Re: Max capacity external memory RAM
Post by: Grumpy_Mike on Nov 15, 2011, 04:45 pm
Well this looks good:-
http://uk.farnell.com/bsi-brilliance-semiconductor/bs62lv1600eip55/sram-16m-2mx8bit-3v-55ns-tsop44/dp/1488953 (http://uk.farnell.com/bsi-brilliance-semiconductor/bs62lv1600eip55/sram-16m-2mx8bit-3v-55ns-tsop44/dp/1488953)

Quote
I need low-latency read/write access to large amounts of memory for audio applications.

Well it's not the memory that produces the limit on access speed (assuming that is what you mean by latency*) It is the things you have to do to generate the address bus and data bus to support the part. You will need a fist full of port expanders and getting data into and out of those will increase the effective memory access time.

Quote
It's a shame no one makes a board that supports this.

They would if they thought there was a market for it.

*Latency is the time between a trigger and the action and the word is normally used to indicate the responsiveness of something in human terms.
Title: Re: Max capacity external memory RAM
Post by: relaxing on Nov 15, 2011, 05:43 pm

Well this looks good:-
http://uk.farnell.com/bsi-brilliance-semiconductor/bs62lv1600eip55/sram-16m-2mx8bit-3v-55ns-tsop44/dp/1488953 (http://uk.farnell.com/bsi-brilliance-semiconductor/bs62lv1600eip55/sram-16m-2mx8bit-3v-55ns-tsop44/dp/1488953)

I'm aware such chips exist. My question was who makes a board that can interface with the Arduino.

Quote
*Latency is the time between a trigger and the action and the word is normally used to indicate the responsiveness of something in human terms.

Yes that is the concept I speak of.
The delays associated with initializing a read/write operation to SD cards are be unacceptable for real-time audio applications.
Title: Re: Max capacity external memory RAM
Post by: Grumpy_Mike on Nov 15, 2011, 05:55 pm
Quote
My question was who makes a board that can interface with the Arduino.


No it was not, your original question was:-

Quote
Hi everyone! I am working in a project about realiable wireless communication, and I need a external memory for store data when the Arduino is out of range. So, my question is very simple. Does anybody know which is the bigger memory RAM that i can add to the arduino? Because the biggest that i found it was 23K256 (32KB), and this is too small. Thanks!


You did not ask about who makes a board you said which is the bigger memory RAM that i can add to the arduino?

Was the phrase:-
Quote
that i can add to the arduino

accompanied by any more information, like I don't want to design it myself I want to buy something someone has already made. If so I missed it.

Quote
Yes that is the concept I speak of.

So that doesn't make sense in relationship to memory access of external RAM. It would only make sense if accompanied with things like sampling rate and number of memory accesses per sample. It is not an inherent function of any particular access architecture.
Title: Re: Max capacity external memory RAM
Post by: Simpson_Jr on Nov 17, 2011, 02:52 pm

No it was not, your original question was:-



Maybe you should check who... wrote what.
Title: Re: Max capacity external memory RAM
Post by: relaxing on Nov 18, 2011, 07:10 pm

If so I missed it.

You didn't miss it. You specifically addressed it one of your posts with a smarmy, off-the-cuff appeal to market economics.

Quote
Quote
Yes that is the concept I speak of.

So that doesn't make sense in relationship to memory access of external RAM. It would only make sense if accompanied with things like sampling rate and number of memory accesses per sample. It is not an inherent function of any particular access architecture.

What are you talking about? Latency is absolutely a quality that applies to RAM, independent of how I access it.
Title: Re: Max capacity external memory RAM
Post by: graynomad on Nov 19, 2011, 12:43 am
How fast do you need? IIRC the AVR will do a native access to the external RAM pretty quick, there may be a wait state inserted I can't remember. But every time you change pages you will have to write to a port and if the access is random you will also have to test the upper N bits of the address for every access

OTOH if the access is in say 32k bursts you can just blat the data out with no address tests.

______
Rob 
Title: Re: Max capacity external memory RAM
Post by: relaxing on Nov 22, 2011, 06:42 pm
I'm looking at audio playback with no human-detectable latency... so I need reads of say 8 words to complete in ~1ms.

I only brought up latency because that rules out external flash cards. I think external RAM should be able to handle the latency requirements easily.

The issue is getting access to enough of it... like a 4 Mbyte chip would be golden.