What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Not all SD cards are created equal...

Sparky

Well Known Member
...at least that's my observation.

When I tried to update the firmware in my dual AFS EF/EM-4500 EFIS installation (not yet flying) several weeks ago, I had difficulties getting the EFIS/EMS units to recognize the SD cards upon power-on.

Without making a short story long, it turned out the problem was the SD cards I was using for the update. I was using 2GB Dane-Elec SD cards initially, since I found them at a better price than the SanDisk 2GB cards originally supplied by AFS. I could not get the Dane-Elec SD cards (yes, I tried more than one) to work reliably, but I finally got one to load after several tries.

So I reformatted on of the SanDisk 2GB SD MAP cards supplied by AFS and it worked flawlessly (but I had to reformat it and reload the MAP software afterwards). Both the Dane-Elec and SanDisk cards were properly formatted to FAT32 per the instructions using Windows Vista and there were no problems reading the cards on my PC, but the AFS 4500's would not reliably read the Dane-Elec SD cards. I may have just gotten a couple of bad cards, or it may be an issue with the AFS units, I don't know.

For the most recent update I went out and bought a couple of SanDisk 2GB SD cards, formatted them to FAT32, loaded and upgraded the software without a glitch.

Lesson learned... (YMMV)
 
I had the same problem using generic SD cards with the 4500. After using the Sandisk brand to install the lastest software on the 4500 the generic cards work just fine. Rob said that the latest software addressed the issue and it did. I flew for 2 years with a 3500 & a 3400 and liked them a lot but I LOVE THE 4500. Larry
 
Yes, this applies not only to AFS but also to MGL equipment.
SD cards are indeed not created equal - there are several standards and not every manufacturer implements things exactly the right way.
We find many cards do not start up correctly when left in the instrument while it is powered up and have not been able to find a solution - the cards do start up communications quite correctly and the system has to wait for a specific message telling it that that card is ready - it never arrives and any attempt at retry fails.
Some older or no-name brand cards also can show strange effects.

Having spent a few gray hairs trying to sort out SD card issues we have also found a worrying tendency of some cards loosing data over time. Further reseach and testing revealed that not only excessive writing to the card destroys it (this we knew of course), but also reading destroys it - just that you can read it a lot more often than you can write it.
This effect is in fact known by the manufacturers of the NAND flash chips used to store the data. Every time a bit is read, it looses a few electrons and eventually the bit "flips". The suggested sulution is to keep a count of how often a card sector is read and after say a few million times, rewrite the sector to refresh the data.

Some of the better, modern SDHC cards do this automatically now and they also start retiring sectors that have been used too often (the card capacity gets smaller over time).
We have found SDHC cards much more reliable and we have moved away from SD cards for all of the above reasons.

I'm not sure if the AFS can accept SDHC cards but if the answer is "yes", my recommendation is to try those, they are much more "bullet proof", so much in fact that we use them as internal "hard drives".

Rainier
CEO MGL Avionics
 
Again, like Ranier and others have said this is not necessarily a limitation of the EFIS but morever likely a limitation of the media. This has been a well known issue as long as there has been EFISes using various cards for updates. Chelton was among the first using SM (Smart Media), as well as others along with way with Compact Flash, USB, SD, XD etc.. If you think SD cards can be cranky, the Cheltons and the SM could make you want to scream sometimes! Anyway, just wanted to re-iterate that even the certified guys can struggle with the media so it's wise to use what they supply/recommend and try not to be pennywise on something like media cards. What I can say is that use of a card is still so much easier than having to plug in a computer so I view that is a plus all the way around!

My 2 cents as usual.

Cheers,
Stein
 
Interesting. I have never thought of Kingston as a 'no name'!...

--Paul

Our very first SD card issues when we first started shipping the Enigma many years ago where with "Kingston" cards. I remember this well.
I have a "Kingston" card here that simply does not work in our systems - but I don't feel too bad about it - if I insert it into the card reader of my PC, the whole PC simply locks up, strangly, it seems to work in another PC, but not very reliable.

A word of warning: If it says "Kingston" or any other brand name on the card, that does not mean anything. Every brand name has been copied in huge quantities and it is all but impossible for a buyer to identify what is the real thing and what just looks like it.
We have gathered a few "real" copies - the only way to identify the copy is to query some of the low level card identification registers and compare these with what the card manufacturer says should be in there. Also, copies usualy are not actual copies - they tend to be low performance cards using the cheapest possible silicon and then all that is actually copied is the label that is stuck on the card and this is then put into a nice blister pack so it looks just like the real thing.
Of course it is fraud, but there seems to be little to no action taken against this...

Rainier
 
Back
Top