AP-16 status LED flashing red

[bsnut]

SD cards with an actual data transfer rate work much better than the cheap ones with no rating.

Brian,

What are you meaning by the "actual data transfer rate"? 

[JonnyMac]

If you look on an SD card should see a C with a number in it, this is a reference to the transfers speed.  In this image:



You can see that this is class 6 card.  A little information on speed class can be found here:

-- http://www.sdcard.org/developers/tech/speed_class/

Still, there is circuitry inside the card that keeps track of usage per area and will spread out the writes so that the memory space gets even usage, since each write operation wears the card a bit.  What this means is that, unlike a real hard disk that can be defragmented, SD cards are almost always fragmented.  Fragmented files take more time to read so the faster the card the better we are.  Here's a blurb from the page I just referenced:

The memory of a card is divided into minimum memory units. The host writes data onto memory units where no data is already stored. As available memory becomes divided into smaller units through normal use, this leads to an increase in non-linear, or fragmented storage. The amount of fragmentation can reduce write speeds, so higher SD card speeds help compensate for fragmentation.

[JackMan]

This is why it's important that the SD card only contains files that will be used by the AP-16+.

[ConceptShed]

Aha thanks that is good info. Both of my cards are class 2 so i guess the 4GB card is under a fair bit of strain. I've ordered a class 10 4GB card, so hopefully that should be ok. When it arrives I'll let you know if it's all good.
It's relieving to know what exactly it is that makes more expensive cards 'better'
Do you know if the 4GB limit to the SD capacity is limited just by the speed of the card in relation to the fragmentation of the data across it? Or is it a different file structuring system?
Cheers anyway

[JonnyMac]

I believe the speed really has to do with the type and quality of flash memory used.  Some vendors probably have better "leveling" firmware that others which probably makes a difference as well.

I have some 2G Patriot branded cards that I bought at Fry's with no specified rating and they work flawlessly.  Sadly, we're going to be faced with these situations when using SD cards with products that require high-speed access.

[ConceptShed]

Thanks a lot for the info. I bought a bunch of Transcend brand 4GB class 10 cards and they all work completely fine. They were the cheapest class 10 ones I found, but so far so good.

I would recommend buying a good class SD card to anyone if you are having issues similar to what's described here.

Cheers for the support.

[JonnyMac]

Do download and install the 1.7 update -- beta tester reports indicate that the increased buffer size allows even "cheap" SD cards to work very well.