SD Card Hidden Text / Error Messages ? - [Solved thanks]

CassLan

I'm running into some strange behavior, where some error messages or warning strings·that are built into the SD Card (perhaps during a format?) are being·placed onto my display.

The thing is that the file buffer that the screen refresh function uses doesn't contain·these characters, so I'm unsure how they are ending up in the Display Drivers buffer.

Does anyone know anything about these strings? I have attached a pic of what I'm talking about.

They are:
Remove disks or other media.
Disk error.
Press any key to restart.

Thanks,

Rick

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Post Edited (CassLan) : 1/14/2010 6:22:06 PM GMT

localroger

These strings are probably the remnants of a bootloader that was installed on the card. If the card were used like a hard disk to boot the device, it would need a program with those kind of prompts.

rokicki

Sounds like something is trashing some fsrw variables, causing the "next block" to be block 0, the boot block.

That would be my best guess.

You can add a function to fsrw that says, if the block we are fetching is #0, blow up with a special error code.

CassLan

After a bit of fooling I can tell this IS being written to the Display Buffer by the ASM routine that I wrote, even though the buffer its supposed to be reading from IS empty.
I have to see what addresses its actually reading from and why.

I bet my code is trashing the fsrw variables, perhaps with an incrementing loop that overflows onto some fsrw values.

Still it was surprizing to see those strings on the display [noparse]:)[/noparse]

Rick

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rokicki

It's also possible that you are picking up the results of the "mount" command. After the mount command, one of the buffers
in fsrw contains stuff like this. Maybe some pointer is going awry and you are copying data from the fsrw buffer after the
mount. If you want to test this, after the mount, make fsrw open a file (any file) and read a single character. If the stuff
changes, maybe to the file contents or to odd junk, then this is probably the problem; you're not copying from the buffer
you think you are but instead from fsrw's buffers.

CassLan

@rokicki,

Thats exactly what was happening, a pointer in the routine was incrementing passed the location of buffer I was intending to read from...and well you know the rest [noparse]:)[/noparse]

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