On May 31, 2016 at 20:13, PeterN said...
Sounds like you're sending a bad command or one that doesn't apply to the state that the TV is currently in. I think I've seen a discrete "power on" do this on some Samsung TVs.
I agree - I control Samsung TVs all the time with serial. Don't usually do volume since mostly use external speaker systems, but I have controlled volume without that message. Sounds like an extra carriage return or something is there. Check the string closely. It should only have (in hex) 08 22 01 00 01 00 D4 for volume up, and 08 22 01 00 02 00 D3 for volume down.