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Thread: [EE] PCMCIA (PC CARD) data xfer to laptop
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face picon face BY : Byron A Jeff email (remove spam text)



On Thu, May 04, 2000 at 02:14:03PM -0700, James Newton wrote:
> I wasn't clear enough... I need to be able to write to this thing from a PIC
> in a remote device. Megabytes of data. Then pick it up, pull the card
> (Compact Flash, SanDisk, PCMCIA FLASH, whatever), push it into the Laptop,
> copy the file or files to hard drive, erase, reinsert into device and leave.
>
> Critical points:
> A) ultra fast transfer speed. 16 Meg in several seconds.
> B) standard unaltered laptop and no fancy software.
> C) multi-meg storage ability.
> D) fairly low power. will only fire up briefly, capture data, then shut down
> so can't be ram or hard drive.
>
> Basically, if I could buy that part of a digital camera...

You can. Just spent a few minutes reading up on CompactFlash for a future
MIDI sequencer project. Basically CF is a flash memory with an embedded
controller that makes it look very much like an IDE device. In fact it has
what's called True-IDE mode that makes it look exactly like a minature IDE
disk. You read/write the disk using the 8 byte IDE task file and the 16 bit
dta bus. The bus can programmatically be reduced to an 8 bit bus if you need
to conserve pins.

Your project would have to maintain a DOS filesystem with a 12 bit FAT. This
limits your filesystems to 32MB but I'm sure you can live with that. Dave
Dunfield has a sample 12bit FAT implementation in C in this file:

ftp://ftp.dunfield.com/embedpc.zip


As for power consumption it seems to be quite small in standby but can grow
up to 90ma a pop when writing. You can probably conserve simply by buffering
512 bytes of data in RAM then writing a whole sector when full.

Interface to the PC is dead dumb simple. Plug in with a CF to PC-Card adapter,
slide into the PC-Card port, treat as a hard disk.

One caveat about True-IDE mode. It does require power-cycling the card to
set this mode as it's detected on power-up. So you need a way to power-cycle
the CF when you remove it.

Take a look here for an Hitachi CF family that has all of the relavent
specifications:

http://semiconductor.hitachi.com/products/product_abstract.cfm?p_id=895

Also Digikey has the 50 pin connectors for CF.

It looks like the winner to me.

BAJ
>
> ---
> James Newton jamesnewtonEraseMEspamspamgeocities.com 1-619-652-0593
> http://techref.massmind.org
> All the engineering secrets worth knowing
>
> {Original Message removed}
<20000504211030.A21844@cleon.cc.gatech.edu>

In reply to: <001101bfb60d$acb90560$0100a8c0@a.efplus.com>; from jamesnewton@piclist.com on Thu, May 04, 2000 at 02:14:03PM -0700
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