Electronics > Beginners
SPI SRAM
Tom Harker:
I need to store a reasonable amount of data and I'm trying (and failing) to find a chip with:
-PDIP/SOIC package (I can solder these)
-more than 4Mb of storage (storing short uncompressed audio clips)
-SPI interface (for lower pin count and to match the rest of the data flow)
-very high endurance read/write
-not too expensive (FRAM!)
I've found VTI7064MSME which fits the bill but it seems a bit dubious and I don't think it has a 'HOLD' pin (to avoid repeat address transmission).
I'm aware there are flash storage chips but they have limited overwrite endurance and I'm trying to make something that will last.
Can anyone help?
Thanks
Benta:
Check ISSI. They have SPI SRAM in SO-8 up to 4 Mb. Good supplier with long life product support.
No affiliation, but I've worked with them and was very satisfied.
T3sl4co1l:
Just how much audio, in total, are you looking to store?
Example, stereo 44.1kHz sample rate 16 bits, is 5.94 seconds. As a continuous circular buffer, a net-size Flash chip will last a week, assuming you need rated retention time. But needing only a 6 second retention time, you'd probably get the better part of a year, maybe several years of useful life, call it planned obsolescence with a graceful failure mechanism (i.e., the audio gradually corrupts with pops and hiss -- which would be a good idea to detect and mute).
Huge Flash chips are readily available. You're literally paying as much, or more, for a small Flash chip, as for a gigabit one.
If this is for brief snippets, forget about it, stuff it in Flash. Even if it's continuous buffering, use Flash.
Otherwise, something like self refreshing DRAM (pseudo-SRAM). No idea if that's available in SPI flavor.
Your PDIP/SOIC requirement is easily satisfied: get a micro-SD breakout board. Now you have oodles of gigabytes on an SPI header. You'll never run out!
I don't get the lack of compression. Even on a $2 MCU, you have enough clock cycles to do at least a simple compression: mu-law scaling, Huffman encoding, various kinds of DCT, or fancier methods like SMASH or lzop or gzip. A combination of these will net you at least a very worthwhile 2x savings, or easily more than 16x if you allow some degradation in quality.
Tim
Tom Harker:
Thanks, I've actually ordered some of these ISSI FBGA chips, at huge expense from mouser.com:
https://www.mouser.co.uk/ProductDetail/870-WVH8M8ALL166B1LI
I don't think I'll get far with them given how tiny they are! I'm sure I've seen a 4Mb SOIC chip from them, but I can't find a place to order it |O
voltsandjolts:
Yeh, I vote for NOR FLASH or SDCARD
e.g. 100K prog/erase cycles, SOIC8 - even the small 64Mbit can be wear levelled to give you at least 64Mb/4Mb= 16 * 100K = 1.6million prog/erase cycles
http://www.cypress.com/file/316661/download
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