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Whistler Wendy's Tips

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WhistlerWendy

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#1
Ok, so "Whistler Wednesday" was a little bit too much to keep up with. So, we're going to go with "Whistler Wendy's Tips"

These may (or may not) come out each Wednesday :)

****So for today's tip:*****

Many of you have questions about Boot/Load times of the Whistler SD card scanners

At boot, the code looks through the entire File Allocation Table, counting “free” clusters.
This is necessary so that we know how much free space is available on the card at startup.
The number of clusters that must be counted is directly related to the size of the card.

As a result, a change in card capacity at a minimum will impact the “Init SD FileSys” time.

In addition to card size, the “Verifying Data” time is dependent on the usage of the card and is heavily dependent on file system fragmentation, used space, etc...

Happy Scanning!
 

pro106import

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#5
So, what is the smallest card you can get away with on a WS1098 if you don't do any recording?
I'm not sure if you can get anything new less than 2GB. Unless you have something in your junkbox that is smaller. The 2GB I am using works fine and loads in a second or 2. I have recorded days and days of activity and haven't filled it. I empty it out every so often.
Doesn't quite answer the question, but it gives my experiences.
 
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#6
So, what is the smallest card you can get away with on a WS1098 if you don't do any recording?
256MB, if you can find one, would likely be plenty if you don't do any recording or logging and don't use "V-Scanner" folders.

The only problem might be getting Windows to format a 256MB card with 32kB clusters (the scanners require that cluster size for speed and memory purposes).

However, I've seen posts elsewhere describing small partitions on 2GB+ cards. Like the 300MB partition described here.
 
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#8
As Wendy said, the scanner spends a bit of time at boot counting free clusters in order to figure out how much space is available on the card.

On a FAT16 card (2GB and smaller), this is both a) the only way to do it and b) pretty fast (a second or two). It's fast because there is, at most, 128kB of FAT data to read.

On a FAT32 card (anything greater than 2GB), it's slower. There's a lot more data to read (more clusters, and it's now 4 bytes per cluster instead of just 2).

Some might note that FAT32 specifies a "FS Info" sector which contains, among other things, a "Free Cluster Count" field. This field, if it's known to be valid, would be a great way to quickly and easily determine how much free space is available on the SD card.

From the portion of the SD card file system spec describing this field:
This field shall contain the last known free cluster count on the volume. The value FFFFFFFFh indicates the free count is not known. The contents of this field shall be validated at volume mount (and subsequently maintained in memory by the file system driver implementation). It is recommended that this field contain an accurate count of the number of free clusters at volume dismount (during controlled dismount/shutdown).

The field is supposed to be (well, it's "recommended that" it be) appropriately updated during controlled dismount/shutdown.

However, there's a potential problem / risk. The "FS Info" sector is sitting right after the Partition Boot Sector and just before the File Allocation Table. Writing data in that area is a bit dangerous when shutting down because "power is going away". A single bit error could wipe out the entire file system.

Another issue: the spec says the field "shall be validated at volume mount". How do you validate it (make sure it's real and accurate) without actually counting free clusters in the File Allocation Table (as the scanner does now)?
 

03msc

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#9
So the solution to get past the now-ridiculously-long 30 second "verifying" step is...what? I partitioned my card and the Init step is a second or less now, so that's great, but verifying takes an excessive amount of time, whether using a 4gb or 8gb card (it's the same).
 

kandrey89

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#12
or just leave it powered up! :)
In a car that's unused 16-22 hours per day? I already have dashcams draining the battery 24/7, I don't need an extra ~3Wh drain.

Uniden doesn't have this problem, so there's a solution. Why do they need to count unallocated space, just write, an if an error occurs due to no space left, well so it does, the scanner will lockup anyway, had a SD write error and it locked up.
 

N6PIV

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#15
I just tried an old 256 Meg card and I am now down to 30 seconds from power on to scan. With a 32 Gig card it is 55 seconds. Hopefully they will find a way to avoid the verifying step.


Sent from my iPhone using Tapatalk
 

kandrey89

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#16
25 secs to verify a 4GB card, it's the original card that came with the scanner.
Previously it was probably only a few seconds using the original firmware 1.0/1.0

Wendy, you seriously need to get rid of this free space verification. What is it for anyway?
If the card runs out of space, it's not like the scanner can do anything about it but throw an error.
 
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Stockholm, Sweden
#17
And please, make that "verifying data" function an option one could select in the menu.

I guess it was only a couple of people that where having problems with corrupt filesystems and probably
only when mobile, so the rest of us users with base scanners doesn't need to be punished from that.

/Ubbe
 

kandrey89

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#18
And please, make that "verifying data" function an option one could select in the menu.

I guess it was only a couple of people that where having problems with corrupt filesystems and probably
only when mobile, so the rest of us users with base scanners doesn't need to be punished from that.

/Ubbe
No, do a proper job and find a solution that avoids corruption and avoids verification. There are ways to write to SD card without corruption, dual configs files, CRC, etc that can be used to keep the scanner stable if it does not shut down properly and happens to corrupt one file or the other.
Don't give us half baked solution. You need to get rid of free space verification and find a robust solution to avoid corrupting the config files so that the scanner can continue to function.

I plan on running mobile, so I don't want to run to a computer everytime your writing scheme craps out and corrupts the card, it'll be twice as hard since it would be hidden in the car.
 

kandrey89

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#20
Whistler is not the only maker having the SD card problem. It is the nature of the SD card scanners.
Really... I've powered off (hard-reset, yanked the power without shutting down) my BCD436HP without batteries for the last 1.5 years, at least twice per weekday and have not had any corruption issues even though I record audio all the time. ZERO!
 
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