Why a file system required in an embedded Device

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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Reply to
Jalon
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A data logger that needs to be read by a PC would need a file system.

h
Reply to
hamilton

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...

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.

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).

Reply to
D Yuniskis

hamilton wibbled on Wednesday 24 February 2010 06:30

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.

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Tim Watts

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Reply to
Tim Watts

n

Sounds like Homework

Reply to
bigbrownbeastie

n

Sounds like Homework

Reply to
bigbrownbeastie

n

Sounds like Homework

Reply to
bigbrownbeastie

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.

Reply to
Paul Keinanen

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

Reply to
tim....

El 24/02/2010 7:12, Jalon escribió:

Third-party software with standard file-based dependencies (web servers, PLC packages, SSL packages... to name a few I have met in real life.)

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Ignacio G.T.
Reply to
Ignacio G. T.

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.

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Reply to
Grant Edwards

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

Reply to
Vladimir Vassilevsky

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

Reply to
Mark Borgerson

Do you have a web site ?

Reply to
hamilton

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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:

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Mark Borgerson

Reply to
Mark Borgerson

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