Electrical – LG RS232 Commands partially working

arduinocablesrs232serial

I have a LG TV (32SL8000), which has a RS232 Control Port. I tried to control it with an Arduino and a TTL to Serial Converter (MAX3232). I looked up the commands from the manual.

Serial.begin(9600);
Serial.println("ka 0 01"); //Turns on TV
Serial.println("ka 0 00"); //Turns off TV

Turning on the TV works perfectly, but any other command doesn't work.

I don't know how to fix this problem.

Thanks for your help

The Manual

Best Answer

I have quite a bit of experience controlling LG displays serially, and while I haven't seen anything like what you report, I can make some observations and guesses that may help:

  1. My LG control code has probably been run against dozens of models by now, and I don't think I've ever run across one that behaved as you say. Then again, I don't think we've yet run across an SL model.

    (Only the two letters in the middle of the model code seem to matter when it comes to compatibility, plus an optional "C" at the end.)

  2. Most LGs accept only power-on commands while powered off, so that you cannot tell "powered off" from "caught fire, fell overboard, and presently at the bottom of the ocean being chewed on by something from an H.R. Giger film." These are the non-C displays, as a rule. "C" stands for "commercial," and this distinguishes models intended for use with automatic control systems.

    The "C" models will often at least accept "power status" commands while powered off, so you can probe it before you send any state-changing commands.

  3. After powering the display on, you have to wait out its 12-ish second warm-up time before you can send anything else. Some LGs will respond with the "OK" reply immediately on receipt of the command, thus leaving the wait time up to your program, while others won't give the "OK" until they're actually ready to accept another command. (The former are more common.)

  4. You aren't by chance plugging the Android board into the USB port for power, are you? If so, that may be enough to trigger this restriction, found on page 112 of the linked manual:

    "During USB operations such as Dvix or EMF, all commands except Power(ka) and Key(mc) are not executed and treated as NG."

You only give the two command strings you've succeded with. What command strings are you failing with, specifically?

Have you tried all the listed commands, or only failed with a few and gave up?

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