Author Topic: SD card area for other data  (Read 5787 times)

Offline FAQ

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SD card area for other data
« on: January 07, 2010, 07:57:11 PM »
Is it possible to have two partitions on an SD card - one with utFAT filesystem for HTTP Server, and the other partition without any file system to store raw data in 512 bytes sectors ?

Offline mark

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Re: SD card area for other data
« Reply #1 on: January 07, 2010, 08:03:25 PM »
Hi

It is certainly possible to have multiple FAT partitions on an SD card - I think that also 4 are possible using the standard partition record. I understand that even more are possible using some extension techniques which I haven’t looked into yet (I think I read something about it though).

However you are not really inquiring about FAT partitions, but more about using ‘unused’ space on the SD card for others purposes.

1)   When PCs or the utFAT module partition a disk they probably try to use as much of the available space as possible. See the utFAT users’ guide example, where there are only about 3k not used on a 2G card.

2)   This can however certainly be changed – there are a few values in the boot sector which inform of the partition size. If these are simply made smaller, the rest of the space can be used for other things. By using low-level access routines data can then be stored in any format (it would, for example, be possible to also have a uFileSystem part on the disc somewhere – or simply binary data… It may also be possible to increase the size of the reserved area of a single partition (this is a define) and use that for other purposes. This may be slightly riskier since I don't know whether there are any rule here about what is allowed - and data output of a partition will however not be protected and a formatting tool may even be able to be used to overwrite it with a new partition (since the data is not in any standard format it would not recognise it any allow it to be overwritten).

Regards

Mark


Regards

Mark


Offline timadria

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Re: SD card area for other data
« Reply #2 on: December 17, 2012, 02:09:04 PM »
Mark,

Is it possible for the µTasker to make these 2 partitions and use them as separate partitions?

Tim

Offline mark

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Re: SD card area for other data
« Reply #3 on: December 18, 2012, 09:48:01 PM »
Hi Tim

The present code supports creating only a single partition on an SD card.

Regards

Mark