Okay I found some cores that work well with the 644P and the SDFat beta listed here compiles and the examples run well.
I'm wondering what the strategy for writing as fast as possible is? With Fat16 I would write to the file and keep track of how many packets I sent, and when I started to approach 512 bytes I would call sync(). I see this library also has a 512 byte buffer. Should I use the same strategy or will this library manage when to sync most efficiently?
also, I am wondering if it is necessary to call close()? This is a data logging app, which means the users are just going to cut power or yank the chip whenever they feel like it. Will that corrupt the file or will we just lose data in the write cache?
Thanks!