Did you check your signals with a good oscilloscope? What you are
experiencing could it be noise or transmission line effects, etc?

Isaac


On 17/03/2015 01:04, IVP wrote:
> Hi all,
>
> I wonder if I've found another, interesting if frustrating, failure
>
> I sorted out the previous s/w read problem by paring the re-
> initialisation routine back to the barest necessities and so the
> read delay now no longer impacts downstream processing
>
> So I expectantly put the card and application s/w on test. You
> may recall this is an 8GB Strontium SDHC and a dsPIC
>
> There are about 60 files, 300MB in total, containg various
> sets of data that are retrieved as and when needed
>
> For the purposes of the test I chose two and accessed them
> continuously and alternately about 1s apart
>
> Sometime during the night, after probably 12 hours running,
> something went wrong. Clk was just going and going when I
> got up. "Oh", I thought. What should happen (and was for
> several hours before I went to bed) is that the dsPIC holds a
> Busy line up whilst reading and processing the file data. It
> drops the Busy line, telling the 18F it's OK to try and access
> another file. So, when I looked at the system without powering
> down, Busy was high and Clk was running. For some reason
> it apparently hadn't finished reading the file. It's only 58kB and
> is normally read in a fraction of a second. It was probably in
> the state I found it in for quite some time
>
> On subsequent re-boots reading that particular file causes the
> same incompletion problem. But it fails to complete anywhere
> from 1s to 15 minutes, which is from 1 to 900 reads at ~1s
> between reads. ie after a re-boot it could fail at any time.
>
> With all the testing taken into consideration, that file has been
> access maybe 40,000 times over a couple of weeks, the
> majority of them on that one day it failed, perhaps 30,000. As
> the FAT is copied into RAM I'm sure it's the file that's broken.
> If it wasn't in RAM then the FAT would have been read twice
> as often as the file
>
> I checked the board but couldn't see any intermittent electrical
> problem. An analyser grab of a failure didn't produce anything
> useful, except to show what I already knew. Clk simply ran out
> of data to get and didn't turn off as the byte count wasn't finished
>
> What seems to have fixed the problem is re-formatting and re-
> loading the card. It's now been running for a day without incident
> and I'll leave it going to see if it fails again in the same way
>
> If reading a file is going to cause it to slowly deteriorate then it
> seems I'll have to put some sort of block refresh regime in,
> otherwise the application is going to fail in months rather than
> decades.
>
> Has anyone had experience or some knowledge of what I've
> seen and how it appears to have been corrected ?
>
> TIA
>
> Joe
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 2015.0.5751 / Virus Database: 4306/9318 - Release Date: 03/16/15
>

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