Re: [Libusb-devel] Using libusb with a USB SD Card reader.

[Tim R. <ti...@pr...>]

Eric Sepich wrote:
> Actually what I have been using is a program called F3 by Michelle
> Machado.

I don't know what that is, and Google was not helpful.

> The program works very well but I am having a very specific issue with
> thousands of SD cards that my client bought. Essentially I can not get
> any SD card readers to read the cards at all. I know it is a long shot
> but I was going to try to write some code at the hardware level to try
> to "wake the cards up" so to speak and make an attempt at formatting them.

Are you aware there are several different kinds of SD cards?  An SD card
reader cannot access SDHC or SDXC cards, and no amount of software or
driver effort can every make it happen.  The hardware is simply not
compatible.

It would be much more productive for you to get some electrical
engineering help to figure out where the problem lies.  Right now, what
you are proposing is nothing more than a shot in the dark.  There is
nothing you can achieve at a low level that the existing drivers are not
already doing.

> I don't think any of you really understand that with tens of thousands
> of dollars on the line that it is indeed worth it to make an effort.

Of course we do.  We all live in the business world in our real lives. 
However, time costs money, too.  Starting from scratch, you are a couple
of months away from achieving your goal.  How much is your time worth? 
Who is paying for that?  Is it your client?  It's quite possible that
the most economic solution is to sell those SD cards on eBay and go buy
another bunch that are known to work.

> Your warnings about how much there is to learn I do heed however being
> a self educated systems administrator as well as a self educated
> programmer in too many languages to list I felt up to the task.
> Mastering systems is something of a lifelong quest for me. In any
> event I am the first to admit that I do have much to learn. Thanks for
> the help out but perhaps I should get a book on programming the USB
> port and start cracking away at that.

USB is the easy part.  The USB Mass Storage Class specification uses the
SCSI command set to communicate with the drive on a low level, so you'll
have to understand SCSI.  The MSC specification can be downloaded from
the USB web site at www.usb.org.  Then, you'll have to understand
partitions and file systems.

-- 
Tim Roberts, ti...@pr...
Providenza & Boekelheide, Inc.