Why a file system required in an embedded Device

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Hi,

I have this question in mind, Why do we need a file system as part of any
RTOS when it is intended for a target embedded device(Low memory and less
storage of data).

I can imagine a system having lots of data managed in terms of files in
need of File system but probably not many embedded devices store that
amount of data.


Is there a particular need/scenario which makes file system required in an
embedded system.


Thnx,
PJ      
                    
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Posted through http://www.EmbeddedRelated.com

Re: Why a file system required in an embedded Device
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A data logger that needs to be read by a PC would need a file system.

h

Re: Why a file system required in an embedded Device
  wibbled on Wednesday 24 February 2010 06:30

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Though there is a compromise position available:

Pre format the media with a simple filesystem (eg FAT but it could be
anything) and pre-allocate one single contiguous file for the whole media.

Let the embedded device have just enough knowledge of the filesystem to
locate the start and size of this file, then maintain the file in an
application specific way (eg simple buffer with a couple of pointers) to a
fixed block size list or something.

This allows the media to present itself naturally to a typical PC but
removes most of the metadata processing overhead from the embedded device.

Let the PC side application worry about interpreting the contents of the
file.

--
Tim Watts

Managers, politicians and environmentalists: Nature's carbon buffer.


Re: Why a file system required in an embedded Device
Hi Jalon,

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Don't confuse RTOS with "embedded".  Many real-time designs are
embedded systems but not all embedded systems are real-time devices.
And, many RT devices don't (!) use RTOS's.

Embedded devices need not have "low memory and less storage".  I'm
working on an embedded system with several GB of storage...

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Why not?  My iPod currently has 35G of music "stored" on it.
It is an embedded device.  And, it is also a real-time device.

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File systems provide a familiar interface to "persistent storage".

Also, if the device has to interface to other devices, it presents
a convenient structure/framework for the transfer of that data.

Real-time file systems present challenges for system designers
(i.e., you can't just port some existing file system implementation
to a real-time environment as most have highly nondeterministic
behaviours).

Re: Why a file system required in an embedded Device
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Sounds like Homework

Re: Why a file system required in an embedded Device
Quoted text here. Click to load it

Sounds like Homework

Re: Why a file system required in an embedded Device
Quoted text here. Click to load it

Sounds like Homework

Re: Why a file system required in an embedded Device
On Wed, 24 Feb 2010 00:12:25 -0600, "Jalon"

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Most real time programmers would like to stay away from any kinds of
mechanical disk drives if possible and hence there is not much of a
need for a file system.

In many RT systems, disk/flash file systems might be usable in the
startup phase to load parameters etc, before the actual RT work
starts.

The null task is also a usable place in doing non-deterministic
disk-I/O.

In actual RT processing, you simply can not use blocking I/O requests
such as typical read/write, but use requests like "read sector 6 track
56", then perform dozens of other operations and at some later time
after hundred of other operations have been performed,  handle the
callback or interrupt service routine that actually returned the
requested data.

While a file system might be usable for loading startup parameters
from a disk/flash and hence require a file system, those systems are a
nuisance for actual RT operations.
 

Re: Why a file system required in an embedded Device
says...
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I've built dozens of data loggers that collect oceanographic data at
120Hz and write it to a hard disk drive.  These are are real-time,
multi-processor systems with one processor dedicated to handling
the storage chores and the other handling the 120Hz data collection.
Coping with the non-deterministic file system does require lots
of buffer space  and lots of testing.   The real tough part is
keeping the average power consumption under 15mA at 7.2V.


Hey---if it was easy anyone could do it and I'd be out of a job!


Mark Borgerson



Re: Why a file system required in an embedded Device

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Do you have a web site ?

Re: Why a file system required in an embedded Device
snipped-for-privacy@nothere.com says...
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www.oes.to

The web site show mainly interface boards for Persistor CF-2 loggers
that are offered for general sale.  They are used by oceanographers
and others for data collection.   The custom loggers that use hard
disk or SDHC cards for storage  were developed for a single research
group and haven't been advertised or sold to others.

The data the loggers collect is discussed in this paper:

http://mixing.coas.oregonstate.edu/papers/mixing_measurements.pdf


Mark Borgerson


Re: Why a file system required in an embedded Device

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Any need for a file system will be imposed by the actual application, not by
the fact that the solution is "embedded" or that it uses an RTOS.

tim



Re: Why a file system required in an embedded Device
El 24/02/2010 7:12, Jalon escribió:
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Third-party software with standard file-based dependencies (web servers,
PLC packages, SSL packages... to name a few I have met in real life.)

--
Saludos.
Ignacio G.T.


Re: Why a file system required in an embedded Device

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You've made a false assumption that all embedded devices have
little low memory require little storage of data.  Some
embedded devices have hundreds of megabytes of RAM and have to
log gigibytes of data from a variety of sources. Filesystems
are great for that.

--
Grant Edwards                   grante             Yow! for ARTIFICIAL
                                  at               FLAVORING!!
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Re: Why a file system required in an embedded Device



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Nothing is requred, except for CPU and power supply. Everything else is
at your discretion. File system is just a matter of convenience if you
need to organize your data.

VLV

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