I've been following this thread and actually got several codes working on my Sammy HLS6187W (which has an actual DB9 for the RS232 port). Odd thing is now, I'm not sure what happened but they stopped working and now I get a single byte response of 0xfd. I've tried factory resetting the TV, turning both PC and TV on/off, reseating the cable, writing the code in different languages (C# and Python). For the life of me I can't figure it out. I did go into the service menu and choose Debug for the RS232 mode. Any other suggestions?