I have done something similar with a 2Mbyte SPI FLASH and an EEPROM
to keep track of positions in the FLASH. I use a block of 16 bytes as
the smallest unit in the FLASH. Every log entry can have a different
length and can contain a different number of blocks. I use a log
header for every log entry which contains the block number (pointer)
of the previous log header and the number of blocks for this log
entry. This way I can traverse the log entries easily for reading,
both forwards and backwards. In the EEPROM I save the next free block
number and the block number to the last written block (to go
backwards from the end when reading). I always write sequentially
from the beginning to the end. For me, the oldest logs are more
important than newer logs so I stop writing when the FLASH is full. I
could implement a circular buffer if the newer logs are more
important than older logs and then I would also need to save the
block number to the first (earliest) log header in the EEPROM.

I use Microchips SPI FLASH routines from the TCPIP stack and these
only erases a page when the first byte in a page is written to so
they expect the FLASH to be written to sequentially, one or several
bytes at a time.

If I would use a circular buffer I would have to keep track of when a
page is erased before written to and if the erased page already
contains log data the block number for the first log has to be
adjusted to the first log header in the next page.


/Ruben


>=20
> Em 22/12/2013 16:05, Andre Abelian escreveu:
> > all, thanks for your replay,
> >
> > my question was about a method to write and read back data and keep tra=
ck of
> > it. I am not sure why do I need to know the page size? I can write even=
 single
> > byte when it comes to erase I will erase all after download all. I am u=
sing
> > SST25VF032 and it is not important to save space at all. mostly the fla=
sh will
> > be empty any way.
> >
> > thanks
> >
> > AA
> >
> >

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124
200 39 Malm=F6 Sweden
Tel +46 40142078
ruben@rjjournal.net
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

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