Main Site Documentation

External Flash


Hi everyone,
Is there someone try connect external flash to cobra to extend storage space for files?
I looking for some solution which replace sdcard with some chip. What Im find until now:
SanDisk iNAND

But both look very expensive…
I need 1-4GB space and I would like use it standard PersistentStorage.

Any sugestion?


Cobra supports SD Card and USB Host.

Can’t you use a SD Card or USB thumb drive ?

May be, you have some other goal ?


I know that cobra support SD Card and USB Host. Currently I use SDCard but in my own designed board with EMX module I would like use some unremoveable storage. So I don’t wan’t that users remove SDCard because then device is not useable(Have settings file on it, log files, http files, xml files with data, a lot of jpeg images…). this is reason why I looking for some “chip” solution which can be harder removed…


You can connect dataflash easily on SPI bus


GUS do you maybe have some recomendation which one I can use or if some of you customer use it?
Something in range 1-4GB …
Will something like this work:
Hynix: HY27UF084G2B-TPCB Link:


Look at microchip and atmel websites


Im check Atmel site:
SerialFlash: It have SPI interface but not enought space(1-64MB)

Im also check microchip site:
Serial EEPROM: Only 1MB
SST Flash: Max 64MB

So nothing do not meet my requirements.


@ Dejan:
The chip you linked to is 4Gb, Gigabits, not gigabytes. That is 512MB.

You should be able to wire it up, but you will have you write your own driver for it.

Also note that NAND is notorious for bad blocks and blocks failing, so you will have to add wear leveling\bad block managedment. Even a brand new NAND chip will have a few bad block which has to be located and skipped.

SD card uses NAND but contains a driver chip that does all this behind the scenes.


Oh! you need something in GB on MB! I am not sure about a good source but I can guarantee it will be allot more expensive than buying an SD card.


You can look at this:
It’s 8Gb, 1GB, and $17 a piece.

From the datasheet:

[quote]Micron NAND Flash devices are specified to have a minimum of 2,008 (NVB) valid blocks
out of every 2,048 total available blocks. This means the devices may have blocks that are
invalid when they are shipped. An invalid block is one that contains 1 or more bad bits.
Additional bad blocks may develop with use. However, the total number of available
blocks will not fall below NVB during the endurance life of the product.[/quote]

[quote]Over time, some memory locations may fail to program or erase properly. In order to
ensure that data is stored properly over the life of the NAND Flash device, certain precautions
must be taken:
• Always check status after a PROGRAM, ERASE, or DATA MOVE operation.
• Under typical conditions, use a minimum of 1-bit ECC per 528 bytes of data.
• Use a bad-block replacement algorithm.[/quote]


how about using an SD Card and seal it with HOT Clue possibly Black Colored and make it look like a big black square of plastic…
and to make it ever more realistic stick a cheap $0.25 chip on top of the hot clue and make it look like it a processor of some sort…
that will throw many people off, leading them to think that the $0.25 chip is actually doing something magical LOL :wink:

just a tough.


MicroSD cards lock in sockets so there is no need to glue anything and they are CHEAP :slight_smile:


Hi Gus,
yes that is true.
but i thought he was more concerned about people hacking his card and getting its content using a standard PC/MAC…

I’m sure what I’ve said is an overkill. but it will get the JOB done… messy but surely :wink:

Or you can always crack open a USB stick and and soldering directly to the BOARD USB Port, by getting rid of the USB Connectors of course. (plenty of those come in very tiny packages)

Good luck.


Then encrypt the data going into the card :slight_smile:


Thanks for responses.

@ Errol: Im miss that they use bits and not bytes. I think that making wear leveling\bad block managedment it to complex for me so Im looking simple solution.

@ Jay Jay: Hehehe what idea :smiley:

@ Gus: I don’t want that everyone who have 5 min free time take sd card out and read it’s content… I think encrypting data on it will slow down device and reading from it a lot. Now reading JPEG image from SDCard and show it on 3,5" LCD take around 2 sec and If I enrypt it with some strong algoritm it will be slower…

Im talk with customer and 64mbit(8MB) SPI Flash will be ok for settings and sensitive data storage other things(Images, http CSS files, and log files) can be stored on sdcard if I can normaly use SPI Flash & SDCard on same time…


And solder the microSD card onto the board.

In stead of hot glue, use thick super glue. I have glue they call miter glue, i think, that is almost gel-like super glue, with an aerosol spray to instantly cure it to a transparent hard plastic blob.

You need special superglue remover to remove it. stuff like acetone doesn’t work.

Just a little heat will soften hot glue. Done it before… :slight_smile:


SPI is new for me and Im see cobra have 2 on it.
Micron have 512Mb Serial NOR Flash(N25Q512A13GSF40F) and also 256Mb Serial NOR Flash(N25Q256A13ESF40G) which will be enought and I don’t need SD card.
Hardwiring flash I think it will not be problem. But what about software side? Will flash react as PersistentStorage or I must manualy write bytes to it and somehow know on which addresses are some files?


If you use a flash chip you will have to develop your own file system. If you use a SD then you get the file system with NETMF.


This is to complicated for me(For now when Im start with embedded systems) :slight_smile:
Maybe Im find solution for me :slight_smile:
I think I will open some USB Pen Drive like SanDisk Cruzer Micro 4GB(or 2GB), unsolder USB connector and put it into PCB board like EMX module and solder it :smiley: On USB Pen as I know I can normaly use NETMF File System :slight_smile:


Great idea! :clap: