"Target error - Medium error" puzzle

I stuck an SD card into my (multi-size) card reader and stuck that in a USB hub connected to my PandaBoard. On attempting to access it, a “Message from SCSI Filer” appears saying “Target error – Medium error”.
Well, I was glad it was only a medium error and not a serious error. :-)
I tried several different SD cards in the same slot of the card reader, but got the same error message. I couldn’t believe all the cards were unreadable. I then looked for a micro SD card to see whether that was readable in the smaller slot, but couldn’t find it.

So what was the problem?

“Medium” is SCSI-speak for the physical media which is storing the data – i.e. a CD-ROM or floppy/hard drive platter. For “smart” media like SD cards the meaning can get a bit muddled (it could be an error with the controller or interface circuitry on the card, rather than an error with the flash chip), but since SD cards are removable and CDs are removable the concept is the same.

If you’ve tried multiple cards, it suggests that the problem exists somewhere between the controller chip in the card reader and the controller chip on the card – e.g. dirty or broken contacts in the card reader, or a problem with the power supply that’s being fed to the card.

A hint: whenever you see “target error”, it is an error (or more precise: something called a “sense key”) from the low level world of SCSI.

In theory, the layers above that low level should have extensive lists of sense keys, sense codes and assorted qualifiers to give users more meaningful errors. However, theory – practice…standards changed over time, the lists got bigger, and many devices just seem to randomly choose those keys and codes and qualifiers, so having such extensive lists would need a lot of work to make them really useful. So RISC OS basically choose to just give the raw sense key to the user in the vague hope that he is an expert that can adequately judge what was really going on.

So whenever you see “target error”, just assume that something deep down went wrong and ignore the text following the “target error” because you now know that it is usually misleading :-)

Maybe the error message could be show the real low-level error in all its sense key/code/qualifier glory to be more helpful when analysing what went wrong? Not sure on what level of the code the error is generated. I don’t even know who handles the decision if a Request Sense command should be done :-(

You overlooked something I said. The clue is there. The card reader is working.
Anyone else?

Anyone else?

Er, yes.

1. You left out the statement that the card reader is working in your first post
2. You don’t say how you’re certain the card reader is working (used on a different system perhaps?)
3. Jeffrey suggested dirty contacts (which would carry over as a fault on other systems) and power (which for a powered hub would again carry over) but didn’t mention possible contact problems on the USB hub to Pandaboard USB – have you tried another USB port?

You overlooked something I said. The clue is there. The card reader is working.

What you said up to now: There was an error when accessing various SD cards you tried.

I cannot find any further clues in your posting. Why you think that the card eader is working is not something that can be deduced from your posting. But I am still willing to help you despite your best efforts to the contrary.

Clue is the penultimate sentence:

I then looked for a micro SD card to see whether that was readable in the smaller slot, but couldn’t find it.

Do you get it now?

Do you get it now?

You couldn’t find any micro SD card? You couldn’t find the smaller slot for the micro SD card (because the card reader probably has none)? You have completely misconfigured your system so that clicking on the icon you thought was the SD card slot was a different slot? You hammered the SD card into the CF slot?

The suspense is killing me.

Do you get it now?

Yes.
You aren’t going to give a complete and coherent list of the symptoms to help people try and diagnose. Steffen also seems to have gained the same understanding.

I came to the conclusion that David tried to make a joke, but nobody is getting it because he posted to “General” instead of “Aldershot”. “Puzzle” probably means different things to different people.

The micro SD card is already in the reader.

That would make sense. Perhaps this card reader just has the various SD slot sizes wired in parallel, so having two media inserted results in fighting and gibberish as interpreted by the system.

nemo has got it. I laughed at myself when I realised that I couldn’t find the micro SD card because it was already in its slot in the card reader. I didn’t see it because it’s so small it hardly shows above its slot.
Has anyone else made the mistake of having 2 SD cards in a card reader? I have never done it before.

As for Aldershot, the only thing I think of is the army barracks. Is it known for anything else other than a ROOL subforum? Why do we name a subforum after an army barracks? It’s barrmy.

Why do we name a subforum after an army barracks?

I suspect that Rick will know, a voice absent from this thread!

It’s an in-joke that was kind of my fault.

Basically, the Aldershot forum was for random off-topic posts. I say “was” because it was reasonably lively and some people objected to the noise… so it’s a lot quieter now.

It is so named because it’s a nowhere place where nothing interesting happens. Just like the real Aldershot – at least, the only thing of interest in the period of circa 1980 to 2002 when I knew the town was a big redevelopment of the shopping centre that was mostly failed when it was clear that existing shops were closing faster than new shops could be created. A quick wander on street view shows so so many bargain/pound shops and places willing too convert stuff into cash. Hmm. I knew Woolies went (cos they all did), but it looks like M&S has also gone. Oh, and the train station, still got that God awful underpass that felt like it was flooded with urine and inhabited by raving lunatics? Some days I wondered if it would be safer just going to the end of the platform and crossing the rails…

Anyway, that’s why Aldershot is Aldershot. ;-)

Another quick Google suggests they want to redevelop the town centre AGAIN. Here’s a hint, ditch the overpriced stupid parking fees. People go to the out of town Tesco because it’s bloody massive and parking is free. In town? A general lack of parking and it isn’t free. You want a better town centre? Have less obstacles in actually getting there. Stuff like that puts people off.

Thanks for explanation, Rick.