it is possbile, but i ask to address these aspect:
a) the ATA protocol is just a subset of the CF standard.
b) IDE/SATA drives implement only that subset.
c) canon uses the CIS and FCR structures which are not part of ATA
-> dumb adapter will not work without software hacks
This information I gathered about the CIS. It is very rare to find a CF card slot implemented as anything other than a hardwired True-IDE device. You can't access the CIS unless the slot is wired as a PCMCIA-type implementation. There's no reason to look at the CIS for a flash disk card; it's only useful for I/O type cards. So, Canon cameras are what, memory mapped I/O cards?
In some situations, you can however use the ATA Identify command to get some vendor information about the card. There's a command hdparm -I (or -Istdout for the raw data) to see what this will give you in a system but not from USB attached device.
To prove the specification I will perform a elementary tests(like in the past);I'll connect a CF microdrive to my Canon 50D,7D, and see if the camera recognizes the card. In theory , this test setup should work. I'll get a microdrive first. I don't care about the transfer rate at the moment, 16Mb/s. We'll see.
To be continued...