Baseband Bootrom Protocol
This is the protocol used to talk to the old, and probably the new baseband, at the bootrom level. The old bootrom didn't have an sig checking, the new one does.
AT 0x30 2 byte length n byte data 2 byte checksum sends A5 on success, 5A on failure
Correct me if I am wrong, but it looks like the last part should be this for the 3G bootrom...
sends 01 on success, FF on failure