Datalogger with Flash

Hi, I have a datalogger with an eeprom memory, and i want to upgrade it
to a serial flash memory.
the problem is that when the memory is full it will start writing at
the begining of the memory, and thats ok with the eeprom, but with the
flash i will have to erase the whole block, so that its not ok.
the message that im writing its 16 Bytes Long. anyone can help me with
that?

Thank you!

peres wrote:

> Hi, I have a datalogger with an eeprom memory, and i want to upgrade it
> to a serial flash memory.
> the problem is that when the memory is full it will start writing at
> the begining of the memory, and thats ok with the eeprom, but with the
> flash i will have to erase the whole block, so that its not ok.
> the message that im writing its 16 Bytes Long. anyone can help me with
> that?

For a flash you need a RAM buffer anyway.
This because the flash is block oriented.
A good path are the Atmel Dataflash, because
they have buffers included.

Rene
-- 
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
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peres wrote:
> Hi, I have a datalogger with an eeprom memory, and i want to upgrade it
> to a serial flash memory.
> the problem is that when the memory is full it will start writing at
> the begining of the memory, and thats ok with the eeprom, but with the
> flash i will have to erase the whole block, so that its not ok.
> the message that im writing its 16 Bytes Long. anyone can help me with
> that?
> 
> Thank you!
> 
If your moving up to a flash part, your increasing your memory size
by leaps and bounds. 2 times, 8 times, 1,000,000 times.

Write your code with the erase block size in mind.

Keep two blocks available, and erase the oldest block.

Which device are you looking at using.

The Atmel devices have 256 to 1024 byte blocks.

You are already over writting 16 bytes in a full eeprom.

Good Luck

donald

"peres" <beto.barba@gmail.com> skrev i meddelandet 
news:1142365844.016078.65940@j33g2000cwa.googlegroups.com...
> Hi, I have a datalogger with an eeprom memory, and i want to upgrade it
> to a serial flash memory.
> the problem is that when the memory is full it will start writing at
> the begining of the memory, and thats ok with the eeprom, but with the
> flash i will have to erase the whole block, so that its not ok.
> the message that im writing its 16 Bytes Long. anyone can help me with
> that?
>
> Thank you!
>

With AT45 Dataflash you do:

    Read Page (256-1024 byte) into SRAM buffer inside the serial flash chip
    Update SRAM buffer with the new 16 bytes
    Write SRAM buffer to Flash

-- 
Best Regards,
Ulf Samuelsson
This is intended to be my personal opinion which may,
or may bot be shared by my employer Atmel Nordic AB 

In article <MeSdnbvMS8UFOorZRVn-iA@forethought.net>, 
donald@dontdoithere.com says...
> peres wrote:
> > Hi, I have a datalogger with an eeprom memory, and i want to upgrade it
> > to a serial flash memory.
> > the problem is that when the memory is full it will start writing at
> > the begining of the memory, and thats ok with the eeprom, but with the
> > flash i will have to erase the whole block, so that its not ok.
> > the message that im writing its 16 Bytes Long. anyone can help me with
> > that?
> > 
> > Thank you!
> > 
> If your moving up to a flash part, your increasing your memory size
> by leaps and bounds. 2 times, 8 times, 1,000,000 times.
> 
> Write your code with the erase block size in mind.
> 
> Keep two blocks available, and erase the oldest block.
> 
> Which device are you looking at using.
> 
> The Atmel devices have 256 to 1024 byte blocks.
> 
> You are already over writting 16 bytes in a full eeprom.
> 
> Good Luck
> 

I handled a similar problem with a logging instrument using am
8 MByte Atmel data flash by:

1. using the onboard 1Kbyte+ (data block size) buffers.
2. Having the data storage wrap around at the end of flash.
   That way you lost the oldest data, but kept the most
   recent megabyte.
3. Using the extra bytes in the block (1024 data, about 32
   'extra' bytes) to keep track of the date and time that
   the block was written, as well as some other session
   data.  It was simpler than implementing a DOS-type
   directory system and wear leveling.  (or so I thought
   at the time.  With the availability of Lewin's
   DOSFS and cheap SD cards, I'm reconsidering for my
   next project).


The problem with this scheme is that you will potentially lose
data in the buffer if you lose power.  I handled this with
a backup battery  and power supply switcher.   If the
main power dropped out,  I wrote the data and went to sleep.


Mark Borgerson

"Mark Borgerson" <mborgerson.at.comcast.net> wrote in message
news:MPG.1e81533d22b13be498a17b@newsgroups.comcast.net...
> In article <MeSdnbvMS8UFOorZRVn-iA@forethought.net>,
> donald@dontdoithere.com says...
> > peres wrote:
> > > Hi, I have a datalogger with an eeprom memory, and i want to upgrade
it
> > > to a serial flash memory.
> > > the problem is that when the memory is full it will start writing at
> > > the begining of the memory, and thats ok with the eeprom, but with the
> > > flash i will have to erase the whole block, so that its not ok.
> > > the message that im writing its 16 Bytes Long. anyone can help me with
> > > that?
> > >
> > > Thank you!
> > >
> > If your moving up to a flash part, your increasing your memory size
> > by leaps and bounds. 2 times, 8 times, 1,000,000 times.
> >
> > Write your code with the erase block size in mind.
> >
> > Keep two blocks available, and erase the oldest block.
> >
> > Which device are you looking at using.
> >
> > The Atmel devices have 256 to 1024 byte blocks.
> >
> > You are already over writting 16 bytes in a full eeprom.
> >
> > Good Luck
> >
>
> I handled a similar problem with a logging instrument using am
> 8 MByte Atmel data flash by:
>
> 1. using the onboard 1Kbyte+ (data block size) buffers.
> 2. Having the data storage wrap around at the end of flash.
>    That way you lost the oldest data, but kept the most
>    recent megabyte.
> 3. Using the extra bytes in the block (1024 data, about 32
>    'extra' bytes) to keep track of the date and time that
>    the block was written, as well as some other session
>    data.  It was simpler than implementing a DOS-type
>    directory system and wear leveling.  (or so I thought
>    at the time.  With the availability of Lewin's
>    DOSFS and cheap SD cards, I'm reconsidering for my
>    next project).

There aren't any 'extra' bytes! They are for error correction codes (ECC) to
correct small numbers of bit errors in the sectors. The devices are not very
reliable - sectors fail or go bad and this situation needs to be detected
and allowed for.

> The problem with this scheme is that you will potentially lose
> data in the buffer if you lose power.  I handled this with
> a backup battery  and power supply switcher.   If the
> main power dropped out,  I wrote the data and went to sleep.

Peter

In article <LwRRf.2417$Tv.2208@newsfe5-gui.ntli.net>, first{dot}
surname@ukonline.co.uk says...
> "Mark Borgerson" <mborgerson.at.comcast.net> wrote in message
> news:MPG.1e81533d22b13be498a17b@newsgroups.comcast.net...
> > In article <MeSdnbvMS8UFOorZRVn-iA@forethought.net>,
> > donald@dontdoithere.com says...
> > > peres wrote:
> > > > Hi, I have a datalogger with an eeprom memory, and i want to upgrade
> it
> > > > to a serial flash memory.
> > > > the problem is that when the memory is full it will start writing at
> > > > the begining of the memory, and thats ok with the eeprom, but with the
> > > > flash i will have to erase the whole block, so that its not ok.
> > > > the message that im writing its 16 Bytes Long. anyone can help me with
> > > > that?
> > > >
> > > > Thank you!
> > > >
> > > If your moving up to a flash part, your increasing your memory size
> > > by leaps and bounds. 2 times, 8 times, 1,000,000 times.
> > >
> > > Write your code with the erase block size in mind.
> > >
> > > Keep two blocks available, and erase the oldest block.
> > >
> > > Which device are you looking at using.
> > >
> > > The Atmel devices have 256 to 1024 byte blocks.
> > >
> > > You are already over writting 16 bytes in a full eeprom.
> > >
> > > Good Luck
> > >
> >
> > I handled a similar problem with a logging instrument using am
> > 8 MByte Atmel data flash by:
> >
> > 1. using the onboard 1Kbyte+ (data block size) buffers.
> > 2. Having the data storage wrap around at the end of flash.
> >    That way you lost the oldest data, but kept the most
> >    recent megabyte.
> > 3. Using the extra bytes in the block (1024 data, about 32
> >    'extra' bytes) to keep track of the date and time that
> >    the block was written, as well as some other session
> >    data.  It was simpler than implementing a DOS-type
> >    directory system and wear leveling.  (or so I thought
> >    at the time.  With the availability of Lewin's
> >    DOSFS and cheap SD cards, I'm reconsidering for my
> >    next project).
> 
> There aren't any 'extra' bytes! They are for error correction codes (ECC) to
> correct small numbers of bit errors in the sectors. The devices are not very
> reliable - sectors fail or go bad and this situation needs to be detected
> and allowed for.

I agree about the estimates of low reliability.  In a data logging 
application as in my project,  I would guess that each block might
get written  perhaps 5 times per year.  That would only happen if
the instrument was sampling continuously---which is very unlikely
as you have to pull it out of the water and clean off the biofouling
on a regular basis.   I was satisfied that checksums would suffice,
as there was significant redundancy in the directory information and
the data consists of individual 4-byte floating point values  where
later values do not depend on earlier values.  Were I working with
a compression scheme or a data format where a single byte error
could compromise a whole block, I would have done things differently.
> 
> > The problem with this scheme is that you will potentially lose
> > data in the buffer if you lose power.  I handled this with
> > a backup battery  and power supply switcher.   If the
> > main power dropped out,  I wrote the data and went to sleep.
> 
Mark Borgerson

Thank you very much!, you have been a great help!

Regards,