I just installed a few of the newer Samsung Smart LEDs and was able to get the Ex-Link working after some trial and error. Well, a lot of trial and error. If the pinout of the interconnect is correct, it should work using these serial specs-

The most important part is that there is NO delimiter after sending commands, so don't tack on a carriage return or line feed. Also, send it as a hex command. Each pair of characters in brackets represent a hex byte, so include or omit the brackets as necessary.

9600,8,n,1

{08}{22}{00}{00}{00}{02}{D6} Power On
{08}{22}{00}{00}{00}{01}{D5} Power Off

{08}{22}{01}{00}{01}{00}{D4} Volume Up
{08}{22}{01}{00}{02}{00}{D3} Volume Down
{08}{22}{02}{00}{00}{00}{D4} Mute Toggle

{08}{22}{0A}{00}{05}{00}{C7} Input: HDMI1
{08}{22}{0A}{00}{05}{01}{C6} Input: HDMI2
{08}{22}{0A}{00}{05}{02}{C5} Input: HDMI3
{08}{22}{0A}{00}{05}{03}{C4} Input: HDMI4
{08}{22}{0A}{00}{04}{00}{C8} Input: VGA
{08}{22}{0A}{00}{03}{00}{C9} Input: YPbPr1
{08}{22}{0A}{00}{03}{01}{C8} Input: YPbPr2
{08}{22}{0A}{00}{02}{00}{CB} Input: Svideo
{08}{22}{0A}{00}{01}{00}{CA} Input: AV1
{08}{22}{0A}{00}{01}{01}{CA} Input: AV2
{08}{22}{0A}{00}{00}{00}{CC} Input: Antenna

Hope this helps!

Edit: Formatting