It took a second to figure out how to format an SDCard with a MS-DOS FAT16 partition, so I wanted to share with everybody. This applies to any type of external disk drive.
There are some links to be found…such as http://www.bergek.com/2008/10/27/partition-usb-disk-with-fat16-on-mac-os-x/ and another one that’s almost identical.
First of all, the second set of instructions result in a “/Volumes/SDCARD/ does not appear to be a whole disk” error in OSX Lion. The drives listed in /Volumes by OS X are the mounted logical drives, and partitioning needs to occur on a physical disk, so I think using “/Volumes/”-anything would not work, but maybe it did in an older version of diskutil.
Regardless, both sets of instructions are approximately the same. When entering this command:
diskutil partitiondisk /dev/disk2 1 MBRFormat "MS-DOS FAT16" "XYZ" 1024M
in OS X Lion I kept getting this error message:
XYZ does not appear to be a valid volume name for its file system
I’m not sure why that isn’t a valid partition name. From what I recall MS-DOS FAT16 partitions support an 11-byte ASCII name. Rather than digging into that I tried this command:
diskutil partitiondisk /dev/disk2 1 MBRFormat "MS-DOS FAT16" "" 1024M
and got the error:
The size (1024M) must not be greater than the size of the whole disk
My SDCard is 1G = 1024M, so I’m not sure why that doesn’t work either. Rather than dig into that hole I used this command:
diskutil partitiondisk /dev/disk2 1 MBRFormat "MS-DOS FAT16" "" 1G
And my SDCard is now formatted. Hope this helps!
UPDATE 8/23/2012: The above worked for a 1GB micro SD card that was used and had been partitioned for an Android G1 previously. On another, brand new SDCard, the steps work but OS X complains that it can’t read the card. Trying to format an SDCard > 1GB is likely the problem – if I find a workaround I’ll post.