0
\$\begingroup\$

I need to connect a SATA device to a development board which does not have a dedicated SATA connector but exposes SATA over a common 2x30 female header instead. My question is what cabling do I need for short length (say 15 cm)? Do I need to bother with cable shielding or is it possible to run SATA reliably over unshielded cable? The setup will operate in a passenger vehicle. The board I use is a phyBOARD-Mira i.MX6.

\$\endgroup\$
  • \$\begingroup\$ It's not possible to connect SATA on normal header connectors. SATA uses LVDS signaling, besides restrictions in shielding and capacity, also the length of wires and it's impedance must match! \$\endgroup\$ – Paebbels Oct 8 '15 at 12:52
1
\$\begingroup\$

SATA employs differential-signalling, which in and of itself, makes it fairly robust in terms of noise immunity. However, the serial data rate is quite high, which may limit exactly which cabling types may work. Over short distances (15cm) even a ribbon cable would likely work, but attention to wiring order may be important. (Note how the SATA cable is wired - differential signals run next to each other, and are separated by ground wires.)

\$\endgroup\$
  • \$\begingroup\$ Thanks for your answer! So is the standard SATA cable (for internal use in PC case) shielded only by wire order? I got an impression that both those differential pairs are shielded like a normal wire - I mean 2 shields with each having 2 differential pairs inside itself. I have not cut a cable yet just to see the reality... \$\endgroup\$ – Kozuch Oct 8 '15 at 11:59
  • 1
    \$\begingroup\$ It looks like from this article that the differential pairs are shielded in a SATA cable. Whether the shield is electrically conductive or not is unknown. The interesting thing is, I expected them to be twisted pairs, however this article shows a cable being shortened, which implies they must not be twisted. In any case, shielding the pairs is a good idea for increased noise immunity inside (an end-user-configurable) PC case. \$\endgroup\$ – rdtsc Oct 8 '15 at 13:53
  • \$\begingroup\$ Most SATA cables are twin-axial AFAIK. The idea is to present a transmission line to the signal and twin-axial was chosen as one of the common transmission line implementations. \$\endgroup\$ – Krunal Desai Dec 24 '15 at 6:10
2
\$\begingroup\$

The biggest problem with a high speed digital interface is not so much shielding but impedance mismatches. You really want to minimise the length of any section with incorrect characterstic impedance.

In your situation I would suggest building an adaptor using wires that are as short as possible and then using a standard SATA cable to connect between your adaptor and the drive.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.