wait_still_screen($stilltime_sec, $timeout_sec, $similarity_level)
Wait until the screen stops changing
Determines the starting offset within the serial file - so that we do not check the previous test's serial output. Call this before you start doing something new
Returns the output on the serial device since the last call to set_serial_offset
wait_serial($regex, $timeout_sec, $expect_not_found)
Wait for a message to appear on serial output. You could have sent it there earlier with
script_run("echo Hello World > /dev/$serialdev");
Wait until the system becomes idle