Connectors on 2.5” SATA to R Pi adapter board

There is a connector, j13, and some empty solder pads, j4 and j9, on the bottom of the 2.5” SATA to R Pi adapter board.
J9 looks like pads for a micro compact flash card socket.
J13 is a connector for a 22 conductor flat ribbon cable.
J4 looks like solder pads for a 22 conductor flat ribbon cable, but no connector.
What are they for?

Hi, these were originally implemented to support a microSD card and camera connector. At that time, the focal application was media player with CM1, so the microSD and camera connectors were not needed, and I believe we never validated functionality. I’ll check with the engineering team.


Thank you for your reply.
I had an inquiry to WD support to find out if the device was compatible
with the RPi Compute Module 3 Lite.
I never received a reply so I bought the WD device and a Raspberry Pi
device anyway. They are not compatible.
The RPi Compute Module 3 Lite needs a compact flash card for the operating
system start up routines, as it lacks the internal memory of the Compute
Module 3.
If the RPi device can read a flash card attached to your device, it could
solve that problem.
If those connections do function, your device could be marketed for more
than one purpose.
The connector at J13 is not quite wide enough for the camera cable sold by
Raspberry Pi, but the terminals are correct spacing in the connector.
I can attach a flash card socket to J9 and see what happens.
There are also empty solder pads at J3. That location is on the bottom of
the board near the micro USB connector J10 on the other side of the board.
It would be interesting to know what was planned there.

Thanks again for replying. I will watch for your info from the engineering


Hi, the team reported that the SATA adapter board’s sdcard layout is not compatible with CM3 Lite. The board will support CM3 (where microSD is not needed because boot files can be programmed on the CM3’s eMMC).

You can, however, use the CM3 Lite in the SATA adapter connected to a SATA drive and implement the MSD (Mass Storage Device) boot feature that can be enabled in Pi3 firmware. You will need a CM dev board (CMIO3) to do this, however. It takes some work to set up because you need to enable the feature in the Pi’s firmware, copy boot and root directory files to the SATA drive and modify cmdline.txt and fstab files to point to the drive instead of sdcard. Forum member whheydt was able to get it working, and his report is copied further below (originally posted on this site). I started working on it last week, but didn’t quite get it to work yet myself (I’ll get back to it in a few days). The R-Pi Foundation provides instructions on setting-up MSD boot, but it requires a CM3 dev board (CMIO3) with sdcard:

Will the MSD boot approach work in your application? If so, do you have a CMIO3 to set-up the MSD boot feature?

If none of the above fits your needs, please send me an email so I can look for ways to support your application (my email:


(Below post from forum member whheydt on CM3L MSD boot:)


Thank you for your reply.

The biggest reason to buy the WD 2.5” SATA to R Pi adapter board Is so the
Raspberry Pi CMio3 board is not required. The RPi board retails for more
than three times the price of the WD board. Buying both is a little much.

I am familiar of the posts on the RPi forums.

I will get out my handy-dandy soldering iron and install a compact flash
socket on my RPi CM3L.

The MSD bit cannot be set without using a RPi CM IO 3 board because the RPi
cm3L must be booted to do so.

I still want to know what the empty solder pads on the bottom of the WD
2.5” SATA to R Pi adapter board at J4, J13,J3 and J9 are for.

Thank you fore your assistance.


J9 is a microSD card holder
J4 and J13 both appear to be CSI interface for RPi camera - same smaller interface as on RPi 0w and RPi 0 2 - I assume for ‘3D vision’ type support
J6 seems to be UART

J3 is still a mystery to me