RS-232 control for LG L4200A

feddx
feddx Junior Member
in NetLinx Studio
Although there is a minute amount of information provided in the manual, I am still having problems. I spoke to someone today at LG. He was able to tell me the trick about jumping pins 4 & 6 on the DB-9, and he gave me some information on their checksumming, but I am still having problems with the interface. The port (on an NI-3000) is set up @ 115200 baud, 8-bit data length, no parity, and stop bit = 1 as described by the manual. I have also tried with straight-through and Null-modem cables (LG specs call for null-modem, but you have to call them to find that out.)

I read this here, but I think that they must be writing about another piece of equipment:

http://www.amxforums.com/showthread.php?t=651&highlight=LG

Can anyone tell me if there is an API for the LG Flatrons? Also, from the documentation I have, it appears that the string you recieve from the device on the power on and off command appear to give you the same results?

I'm tempted to ditch the whole idea of serial control of this device altogether.

Help me......
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Comments

  • sonny
    sonny Junior Member
    According to their docs they do not use any handshaking, so jumpers on pins 4&6 shouldn't matter. What port are you using on the NI? I have had problems with devices that communicate at higher baud rates on port 1. Move to 2 or 3 and try that.

    Also, they don't provide their checksum algorithm in their manual. Looks though like it is probably a simple addition of some or all of the packets bytes, then AND with $FF.

    Finally, looks like an address byte is important.
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  • feddx
    feddx Junior Member
    sonny wrote:
    According to their docs they do not use any handshaking, so jumpers on pins 4&6 shouldn't matter. What port are you using on the NI? I have had problems with devices that communicate at higher baud rates on port 1. Move to 2 or 3 and try that.

    Also, they don't provide their checksum algorithm in their manual. Looks though like it is probably a simple addition of some or all of the packets bytes, then AND with $FF.

    Finally, looks like an address byte is important.


    Whe I spoke to them, they told me that jumping 4 & 6 together at the device was essential. This is apparently how the Display "knows" it is to recieve RS232.

    The checksum algorithm is simply add all of the bytes and subtract from $FF

    I was hoping that someone was cuurntly using these displays and could shed some light as to their control.
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  • tom goez
    tom goez Junior Member
    I have controlled many LG 60" plasmas and used no handshaking.

    Send along your string for Power ON and let's take a look at it.

    Tom
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  • feddx
    feddx Junior Member
    Thanks for getting back to me Tom.

    Here's what I'm sending for the power on:

    "$08,$6E,$00,$03,$01,$00,$01,$85"

    This is according to their manual and the single page I was "faxed" (the technician did NOT have an electronic copy!) by them about the checksum value. Add the first 7 bytes ($7B) and subtract from $FF and add 1.

    And my power off is:

    "$08,$6E,$00,$03,$01,$00,$00,$86"

    What concerns me is the addressing. Byte 6 is supposed to represent an address that you set by blindy firing a command at the device. Is there ANY other way to see if you have connectivity with these devices?

    Thank you in advance for all of your help.
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  • tom goez
    tom goez Junior Member
    The hex characters you have are correct. The method of calculating the checksum is correct.

    Are you using send_string or send_command? You must use send_string.

    If you are using Axcess programming language, you can create a buffer on that device and store the characters in a variable to look at.

    If you are using NetLinx programming, use a data_event to capture the strings coming from the device.

    The baud rate you have is correct, and use a crossover cable 2-3 & 3-2 and 5 for signal common. It should work.

    I have attached the protocol I got from LG (in Excel format), but it is pretty sparse. The protocols for the LG 60" plasma is right in the owner's manual and is concise.

    Tom
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  • setholle
    setholle Junior Member
    LG 42 inch problems

    The hex code you have is correct.
    HOwever I have worked with these.
    There is no way to get correct feedback from the l4200a according to Lg.
    I talked to the engineer in chicago.
    Seth Olle
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  • tom goez
    tom goez Junior Member
    Feedback from L4200

    It's hard to believe there is no feedback available. Have you tried to make a data_event and see what is coming back from the unit? Serial control without some sort of status feedback is bad design since the program you write will not know what's going on when something happens!
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