compact flash

[Bernd Felsche]

alexpeper writes:

>From: Bernd Felsche <bernie at perth.dialix.com.au>

>>How hard is it to drive a compact-flash? I'm considering it as an
>>option for data-logging using the SPI from an Atmel 8535...

>>Any definitive URL's with spec's and supplies for connectors, etc.
>>would be welcome.

>This would be of interesting thread for diy-fi since seems to be
>settting standard in memory in small devices, digital cameras, mp3
>players etc. thus reducing cost.  diy-fi is a memory intensive
>operation with  multi megabyte capacity his could provide less
>interpolation, more tables, data acquistion and improved adaption.

I wouldn't hold my breath on being able to get to the data in a
truly random way really fast... Data access is often by "page" and
through a serial interface.

However, it's perfectly adequate for data logging at sustained
speeds of around 250,000 bits/second if those data are stored
"serially".

>I am still somewhat confused on reliability of writes. and write
>times compared to EEPROM.

The Atmel devices (chips) are equipped with two buffers, you fill
one while the other is flashed to permanent store. Flash times are
in the order of 7 to 15 milliseconds for a 528-byte "page".  (Hence
the bandwidth limitation.) The Atmel chip (AT45DB161) I looked at
could be clocked at 13MHz, giving burst data transfers at around 1.5
megabytes per second. Reading from flash to buffer happens at as 250
to 350 microseconds allowing serial reads at full clock speed.

Random access is another game altogether - the 2 on-chip buffers of
528 bytes each need to be filled if the data required is at an
address not already buffered. You probably don't want to "spin"
waiting for the data! It may be used however, to assist in long-term
adaption and keeping a history of operating conditions.

Writes are pretty good in reliability; the chips themselves have
internal readback and compare with buffer - unless they are really 
cut-down (per-)versions. Only when you exceed the "life" rating of
the devices, do persistent storage problems arise.

However; I'd prefer (due to cost) to work at the commercially
pre-packaged CF level; I get zillions of hits on web searches but
the interface details are sketchy - haven't been able to find a
CF-socket either.

-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
     http://www.perth.dialix.com.au/~bernie - Private HP
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org