Disk drive using loopback to calibrate transmission amplitude

A disk drive for connecting to a host, the host comprising loopback circuitry operable to loop a pattern received from the disk drive back to the disk drive, the disk drive comprising:

• (a) a disk;
• (b) a head actuated over the disk;
• (c) interface circuitry for interfacing with the host, the interface circuitry comprising:
• a transmitter driver operable to transmit transmission signals at a transmission amplitude;
• and
• a receiver driver operable to receive reception signals;
• and
• (d) control circuitry operable to calibrate the transmission amplitude by:
• configuring the transmitter driver to transmit at an initial transmission amplitude;
• transmitting a calibration pattern to the host through the transmitter driver;
• monitoring the reception signals received by the receiver driver to detect a loopback pattern representing a loopback of the calibration pattern;
• processing the loopback pattern to detect an error;
• and
• adjusting the transmission amplitude in response to the error.