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Design of an embedded logging system
snowsara
#1 Posted : Friday, January 25, 2013 1:00:38 AM(UTC)
Rank: Newbie

Joined: 1/24/2013(UTC)
Posts: 1

Hello everyone,

I am designing an embedded system whom goal is to log sensors state continuously and that can be powered off at any time.

For specific reasons, I have currently to use Windows XP, and a Compact Flash storage media. Firsts prototypes use this configuration :
* 1rst partition readonly for the system (NTFS),
* 2nd partition for data logging (NTFS).
First tests are not so bad, but I am not fully satisfied of this solution (time to time filesystem or Compact flash is dead).

Do you have advices about a way to improve the solution that I am validating ?
Which solution would you use (HW is x86) if Windows XP and a compact flash were not a constraint (which storage media, which filesystem, which os configuration, etc.) ?

Thank you for your advices
Johan Dams
#2 Posted : Friday, February 01, 2013 3:58:42 PM(UTC)
Rank: Advanced Member

Joined: 9/16/2012(UTC)
Posts: 35

Hi.

First off, I got a little surprised reading WindowsXP and Embedded in the same sentence :-)

I'll start by replying to your post from the bottom: if I had to use x86 and would be allowed to pick my own OS, I'd go for Linux. At least I would be able to run the thing headless. I must admit though that for a simple application like logging sensor information (by the way, how many sensors? What data rate are we talking about?) I'd go for something much smaller, like an SOC based system or even micro controller based.

Selecting the medium on which to log your data depends on your data rate, so not too easily answered and some more details would be welcome. If this is one box standing in the corner (and assuming a big OS like Linux on an overly powerful processor), you could go for a RAID setup of a bunch of hard drives with mirroring and something like ZFS or XFS.

When you say "powered off at any time" what do you mean with that? Hot power off without proper shutdown? In that case, definitely not Windows.

Perhaps you can give us some more background information, so we can answer your post better. Personally, when I see sensor data logging I think of tons small embedded systems talking to a server somewhere over a network where the data gets logged into a powerful database server ready for analysis.


Johan.
Erkki
#3 Posted : Sunday, February 03, 2013 2:40:26 AM(UTC)
Rank: Newbie

Joined: 2/3/2013(UTC)
Posts: 1

Hi.

About compact flash.. we had similar problem. Eventually they become dead (most likely due excessive file access. Don't know for sure). One workaround for this is to keep sensor data in memory and then write changes of states periodically (minimize writes to cards).

Can you check your CF cards? Some of them does not have good wear levelling systems and will die faster.

Remote reading of sensors over network would be good idea (like Johan mentioned in his answer) in general.

Erkki
Finland
cdhmanning
#4 Posted : Sunday, February 10, 2013 1:35:06 PM(UTC)
Rank: Newbie

Joined: 10/24/2012(UTC)
Posts: 2

I would certainly use Linux rather than Win anything. Linux provides many more file system options to choose from and you have a far better chance of finding a more robust FS.

There are at least 3 levels at which the system can be corrupted:
* At the application level.
* At the file system level.
* In the CF card itself.

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