I received a Seagate 7200.11 hard disk in a BSY (busy) state. The hard disk drive spins, but it’s completely invisible to the BIOS. Apparently all these models are affected by a bug in the drive’s firmware: ST31000340AS, ST3500320AS, ST3750330AS and others too.
I found this very well written guide on how to fix the BSY state on Seagate 7200.11 drive. I needed some sort of serial TTL adapter to hook up to the drive’s serial port, but didn’t have one at hand. Then I remembered that I have an Arduino clone Freeduino lying around and I knew that it already has a FTDI chip that does the USB to serial conversion for the Atmega chip. Ok, so it’s not technically Arduino AVR chip used to fix the drive, just the board.