Aaeon SBC-551 Manual page 36

You can connect an LED to indicate that an IDE device is in use.
The pin assignments of CN1 are as follows:
Pin
1
2
You can attach two Enhanced Integrated Device Electronics hard
disk drives to the SBC-551/552's internal controller. The card comes
with a 40-pin flat piggyback cable. This cable has three identical
40-pin flat-cable connectors.
Connecting drives is done in a daisy-chain fashion and requires
one of two cables, depending on the drive size. 1.8" and 2.5" drives
need a 1 x 44-pin to 2 x 44-pin flat-cable connector for CN6. 3.5"
drives use a 1 x 40-pin to 2 x 40-pin connector for CN5.
Wire number 1 on the cable is marked as red or blue, and the other
wires are gray.
1. Connect one end of the cable to CN5 or CN6. Make sure that
the red (or blue) wire corresponds to pin 1 on the connector,
which is labeled on the board (on the right side).
2. Plug the other end of the cable to the Enhanced IDE hard drive,
with pin 1 on the cable corresponding to pin 1 on the hard
drive. (See your hard drive's documentation for the location of
the connector.)
28 SBC-551/552 User Manual
Signal
-R/W IDE
VCC