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Flash translation layer for NAND flash

Posted by rasty1 on July 18, 2016

Hi, Is there any recomended basic translation layer for NAND flash for FreeRTOS+FAT? 1. Bad sector list 2. Wear levering 3. Error detection 4. Redundant FAT

Purpose is firmware storage and logging of non-critical data.

Thanks Rasty

Flash translation layer for NAND flash

Posted by heinbali01 on July 18, 2016

It would give me headaches to write an efficient and fast and low-RAM FAT-driver for NAND.

You have to deal with an ERASE size of more than one block. Erasing means: writing "all ones". When you want to change one 512-block, you probably have to read/erase/write a much larger block of e.g. 2 or 4 KB.

For most projects where +FAT is needed, I would use an SD-card. SD-cards are optimised for FAT tables if you store the table after an offset of 4MB from the start. That part may be re-written much more often than any other part of the card.

As far as I know, a NAND flash chip has homogeneous memory, which can be re-written N times. You will have to write all logic that an SD-card will do for you. You will also have to deal with bad sectors: mark them as bad and repair a file system.

Depending on the data needs, you can also decide not to use a file system on NAND.

I hope that someone else has a more optimistic view on this :-)


Flash translation layer for NAND flash

Posted by rasty1 on July 19, 2016

Hi Hein, You're right . SD card or eMMC is simple and reliable option, but not every MCU can load/boot from eMMC. Some commercial file systems provide that layer. Flash block handling is major IP. Thank you very much for the reply.


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