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hello all from Edmonton, Alberta

Iron

Good presentation.

One article that fills in some of the blanks and amplifies this presentation can be found at:

http://en.wikipedia.org/wiki/File_Allocation_Table

Does anyone else have a favorite article to share on the subject

I got new knowledge about FAT based filesystems ecosystem
Iron
thank you. Eric, nice job.
Iron
as always, MS has patents for obvious things. Slightly bad news, fortunately VFAT or exFAT needed for Windows communication by via card only. So long file name support really do not have be realised if we count using card exlusively inside embedded system.
Iron
Nice presentation as always - slides and audio track
Iron

Good information, see you tommorrow.

Iron

Great info. Thank you, see you tomorrow.

Iron

Thanks Eric. Yes I am planning to use USB storage on a Embedded system.

Iron

Thank you. See you tormorrow

Iron

and yes, the file size in directory entries for files is needed because although we have a fixed amount of storage space allocated, the actual file will probably be smaller and hence we need to know where it actually ends.

Blogger

Thanks everyone for attending, I hope to see you again tommorow for the lecture titled "Balancing Performance, Safety and Resource Usage in an Embedded System".

Blogger
Mark1200: yes, you are right, the first LFN entry is the one that immediately precedes the normal directory entry. The last one is the first that appears in the directory table and it has a specific bit in the sequence number that indicates that it's the last entry.
 
Blogger

Thank you for today's presentation Eric

Iron

Did not realize that there was a patent on FAT.

gbegin: the correct way of handling that would be to ignore the directory entries and eventually free them for further use.

Blogger

gbegin: it's actually not CRC, but a checksum of the DOS (8.3) filename, so that it can make sure that the LFN directory entry really goes with a specific normal directory entry.

Blogger

gbegin: not sure, I'd like to check before I say anything wrong, but I think the LFN entries should be ignored in that case.

Blogger

Atlant: they're using some workarounds that they claim does not infringe Microsoft's patents. Microsoft did go after linux-based products (TomTom), however.

Blogger
mharkins: It's hard to say if exFat will get widely adopted. For now, its adoption is slow, but with the Secure Digital Association adopting exFAT as its recommended file system for SDXC cards, it might become more widespread.
Blogger

Does anyone know: With Linux, who's paying Microsoft their $0.25/copy for the use of their patent on LFNs?

Iron

Altant: yes, NAND flashes have a spare area that can (and must...) be used for Error Correction Codes (ECC). Without those, you can expect your file system to become corrupted really fast. HDDS also have OOB storage for ECC, but that's all hidden by the controller.

Blogger
srdmahesh: It would depend on your application, if you need to interoperate with a desktop PC either through a removable media or through USB Mass Storage Device Class, having FAT is certainly a good bet. If that's not required, FAT might still be a good choice since it's relatively lightweight. Also, some journaling add-ons can make it more reliable and protect it from unexpected power-losses on embedded systems where you're exposed to unexpected power-losses

 

Blogger

bitbanger: Most Flash memories have extra "Out-of-Band" data storage for the necessary CRCs/ECCs.

Iron

The low level disk interfaces save track/sector and crc for each sector as part of the magnetic patterns, historically. So for data integrity, something like that would need to wrap the data when saved to EEPROM or Flash.

Alaskaman66: there are no CRCs for data in FAT, only for LFN file names.

Blogger

Alaskaman66: Yes, any checksums that you (as a user/programmer) write are just ordinary data to the FAT32 filesystem.

Iron

jcabacas: well it`s similar to FAT, but has significant differences which means that a FAT compatible system will not be able to read an exFAT volume.

Blogger

@Eric.  Well, how likely is it for SD cards to move to exFat then?  (Or do I need to plan on re-writting the FAT32 embedded code I'm just getting ready to release! 

Iron

If your data is using something like CRC for accuracy, is this seperate from all the file system checks?

is exFAT compatible with any previous version of FAT filesystems ?

Iron
mharkins: exFAT volumes can't be read in systems that don't have exFat specific support, if that's what you meant
Blogger

In our case, *CERTAIN MODELS* of USB sticks were indicating that they had finished writing before they actually had, so the power-cut that followed was causing the last several writes to not actually get committed to the Flash media inside the USB stick. This led to corrupted FAT32 file systems.

Iron

Speaking of file corruption, I see that there is a checksum in the LFN field. I would like to know:


* what is protected (covered) by the checksum

* what happens if it fails

Iron

Yes, we have had data once in about 1 year. Using a 2GB SD card & running the ChanFAT FS. We are not sure what caused it

Iron
mharkins: Did I say 2GB for file size limit? Should have been 4GB, sorry.

 

Blogger

First time I'm studying File systems.... A lot to learn.

Thanks Eric

Iron

Or did you miss speak and its the 4G shown on your slide for Fat 32, without using extended Fat?  ALso, is exFat backwards compatible with fat32?

Iron

Yes, data corruption on embedded system, USB thumb

You said file size was limited to 2G on Fat 32, its 4G due to the 32 bit variable for file size isn't it?

Iron

Thanks Eric. I learnt more from this ;ecture.

 

Iron

Do you recommend any particular File system for low power embedded design ?

 

Iron

Have had data corruption on power down. Fixed by using an EEPROM with power down protection. 

Iron

Thanks Eric, Lauren, & Digi-Key

Iron

Intermediate writes to FRAM or NVRAM in case of power failure

No, I have not done yet

Iron

Thank you Eric. Very interesting

Iron

No Experience.

Thank you Eirc and Lauren.

Iron

Thank you for the lecture.

Iron

no curruption for any of the embedded FAT stuff I have done

Iron

No data corruption yet.

 

Iron

FS. Where and what?

Iron

No data corruption problem; Thanks Eric & Lauren

Iron

Yes.  I have a version of CHKDSK with auto correction that runs on our embedded system.

Iron

Have not worked with embedded systems, yet.

Iron

Not as of yet, but just getting started with embedded filesystems.

NA I have not done any FS in embeded

Iron

Not ran into any data corruption on the embedded fat systems I've done to date. 

Iron

no data corruption issue so far

 

Iron

Never experienced data corruption

Iron

Yes, data corruptions on USB sticks.

Iron

Thank you for showing the slide number

Iron

@bartholemew: slide 24 - chewing the FAT

Iron

naval: How long do you like your filenames to be? ;-)

Iron

What is the typical need for LFN?

The order of the file name segments in LFN entries is not as expected.  The last segment is in first directory entry used by the file name.

Iron

Alaskaman66: No, just one cluster-size per FAT32 volume.

Iron

answer to file size why needed is that the bytes in a file may not be the same as the bytes available in a sector so an exact file size would be needed.

Iron

Can you have more than one cluster size in a file system?

Efficency when listing directory contents

 

Iron

clusters may not be entirely full

Iron

It let's you know the file size without actually reading the file.

 

Iron

Since file size is not necessarily an integral number of clusters, an expl;icit file size is needed

Iron

File size needed in case of file corruption.

Iron

You need file size so you can allocate memory in system memory to store the file when reading it.

Iron

two checks to check in the event there is an error

Iron

the file may not fill the last cluster...

Iron

Size of File is required because File sizes will not necessarily be multiple of power of 2.

If EOC corrupted, file size is backup

Iron

file size not guaranteed to be an integral number of clusters

 

Iron

CPM used an EOF character (CTRL-Z ?) to mark end of text. MSDOS FAT has a byte count to allow file granularity of byte.

Full clusters aren't always used.

 

double-checking like parity code?

 

Iron

The file may not fill the last cluster.

Iron

bitbanger55  The slide presentations for the Wednesday through Friday courses have been fixed. Thank you so much for bringing that to our attention.

I had no problems with sound yesterday. Today it brakes very often

Iron

I guess I'll catch it in the archives!

 

Iron

No audio problems on firefox (behind a corp firewall)

Iron

@srdmahesh are you behind a firewall?  BlogTalkRadio may be blocked

Iron

Also, try Firefox or Google Chrome is you're having trouble using IE.

Right above Eric avatar at the top of the Classroom page,click on the sidebar

Iron

loosing audio periodically

Iron

audio is great, just try refreshing and hit play button on left hand side

Iron

I am not able to see the audio play button

 

Iron

Hello from wet Huntsville, Al

Iron

Look like some of us don't have any audio connection...

Iron

Yes, and we are on slide # 3

@rnotani...yes

 

Iron
rnotanirefresh and hit play button
Iron

have we started yet?

Iron

Good afternoon from Moncton.

Good afternoon from Montreal

 

Iron

@rruther2 - it means we are not pretty, but we are strong and carry most of the load

Iron

Good evening from Iasi, Romania

Iron

Hello from Edmonton, AB

Iron

CurtD: Used to live in Skokie back in the day.

Hello from cloudy Atlanta

Iron

@Lauren Musket, what does GOLD mean?

I hear that IRON is Information Radio Online Network

gut, SILVER and GOLD ???

Iron

Good Morning from Sunny Valdez.  Two hundred sixty inches of snow so far this year

Good morning, everyone... Sunny day here in Chihuahua Mexico... No wind, no cold... Nice weather today =)...

Iron

@levitonDave  LOL Speak for yourself :)  We've had some where we live in Gresham.  But I agree, nothing like what's going on in the midwest and back east.

Iron

Hello from Millington Michigan

Iron

The streaming audio player will appear on this web page when the show starts at 2pm eastern today. Note however that some companies block live audio streams. If when the show starts you don't hear any audio, try refreshing your browser.

Platinum

@vsrollins - you have my sympathy. I moved away from Milwaukee to get away from the snow. Portland really doesn't see much of that (none for the year :) )

Good luck and keep warm.

Greetings from eastern Mass.

Iron

Hello from Lynn Haven Florida

Iron

Digging out to say hi on a snowy Chicago day!

Iron

Hello from Chicago

Iron

hello from Ottawa, ON.

 

Iron

Good morning everyone.

Iron

Good Morning from San Jose, CA.

It's 46°F right now with a High of 62°F. Expecting Rain tonight,

Iron

The downloads for Wed-Fri have mis-coded links. I was able to hand edit the URL to match today's version style/base . Then they downloaded and converted fine.

Greetings from Vermont - @bartholemew - good one - Isn't that also known as a corrupted directory?

Iron

Good Morning from CLOUDY Boston!

Iron

Hi There from Toronto

 

Iron

Here's hoping everyone survives the impending snow storm in the midwest and coast.

Good morning from Portland Oregon

 

Iron

Good Morning from Mobile, AL

Be sure to click 'Today's Slide Deck' under Special Educational Materials above right to download the PowerPoint for today's session.

Platinum

Good morning from Milwaukee!

Iron

Good Morning from GA

Iron

Looking forward to chewing the FAT.  ;)

The slides are super as usual

Iron

Slide Deck Downloaded... Just waiting for tomorrow's session =)...

Iron

Yeah, FAT is old but venerable.



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