Hi developers,
while using the LogStorage component of the at45db chip,
in circular mode with a volume consisting of n pages,
I observed the following:
I. After erasing the chip, writing n-1 pages,
and triggering a reset of the mote, no further writing
or reading is possible.
The reason seems to be procedure locateLastRecord()
in tinyos-main/tos/chips/at45db/LogStorageP.nc.
496 void locateLastRecord() {
497 if (firstPage == lastPage)
498 {
499 /* We walked all the way back to the last page, and it's not
500 valid. The log-volume invariant is not holding. Fail out. */
501 endRequest(FAIL);
502 return;
503 }
...
For a dirty workaround I replaced
if (firstPage == lastPage)
with
if ( (firstPage == lastPage) && (metadata.pos/PAGE_SIZE != lastPage) )
but this probably violates some assumptions or invariants.
II. After erasing the chip and writing x pages,
the following number y of pages can be read:
If x < n, then y = x.
If x >= n, then y = n - 2.
That means that if I write at least n pages, then I lose
the n-th and (n-1)-th "newest" ones.
I am aware that these observation
are possibly due to errors
in my test application but
maybe you can give me some hint --
I am grateful for any help.
Best regards,
Michael Rink
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