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RS232 DVD Issues

JeffJeff Junior MemberPosts: 374
I'm trying to control a JVC DVD/VCR Combo Deck that I'm having a bit of trouble with. The protocol has two types of commands in it: single hex character commands, and multiple character commands.

The single ones work perfectly. I send $3A to the unit, it plays. No problem.

The issue I'm running into is with the multiple commands. I want to switch the deck from DVD to VCR. As far as I can tell, this is the "Command Target" command ($F0). The way I read it, $F0 says you're switching devices, followed by $30 for VCR and $38 for DVD. Unfortunately, if I send "$F0,$30", I get no response. If I send "$F0,$38", I get no response. If i send "$F0" I get no response. If I send "$30" I get no response.

I'm fairly sure this is user error. Can anyone point out what I'm missing here?

Also, I did try this on a few other commands that were structured the same way, and had a similar lack of results.



  • Joe HebertJoe Hebert Junior Member Posts: 2,159
    Did you try the single commands $43 and $44 on page 5?

    My best guess is that $43 switches from DVD to VCR and $44 switches from VCR to DVD.
  • VLCNCRZRVLCNCRZR Senior member Posts: 216
    JVC combo RS232

    For the JVC SR-MV55U, I have had success with using $43 to select VCR,
    and $44 to select DVD.

    Precede both with a $9F with a small delay between and it should work.
  • Thomas HayesThomas Hayes Junior Member Posts: 1,164
    I had some issues with these decks and had to adjust the pulse rate for the menu and related commands, the normal commands such as play and stop worked fine.
  • JeffJeff Junior Member Posts: 374
    Thats obnoxious. I have to send the commands back to back, but I have to build in a wait between them? Why can't we just send a command?

    Got it working though, so thats really all that matters.

  • HedbergHedberg Junior Member Posts: 671
    Jeff wrote:
    Thats obnoxious. I have to send the commands back to back, but I have to build in a wait between them? Why can't we just send a command?

    Got it working though, so thats really all that matters.


    We had one of these a couple months back. In the manual in the RS232 section it says:
    "During command transmission, a minimum of 50 mm/second is required between each command." I never measured time in mm/second before -- I presumed that 50 ms was meant. If I recall correctly, if you wait too long between the commands, it won't work either. This caused problems when trying to test commands by entering them through a telnet session. Ended up with a queue sending commands at 150 ms intervals and that seemed to work ok.

    Another cute thing about this deck is that the RS232 goes to sleep when you power the deck off with the power save feature engaged. It's "on" by default. After about 10 seconds with the power off, it won't respond to a power on command.

    Other than that. it turned out to be a pretty good deck.With a couple "sense" commands ($D7, $D8, and $D9) you can get the deck to give you lots of status and time information. You can create a pretty thorough status display on the TP.
  • gregrgregr Junior Member Posts: 54
    Parsing data?

    Any tricks to parsing data back from this deck? First device I have dealt with that has no delimiters in the return string.

  • adimexadimex Junior Member Posts: 21
    CHARDM-65 worked fine for me....
  • kbeattyAMXkbeattyAMX Junior Member Posts: 358
    Errors with JVC

    Keep in mind that this deck frequently goes into ERROR MODE. Meaning that once it has an ERROR the ERROR needs to be cleared before any communication can continue. Once you receive an $02 you need to send an $56.
  • gregrgregr Junior Member Posts: 54
    adimex, does the CHARDM affect the strings going into the Netlinx buffer from the deck?

    The short description in the manual seems to indicate that it delays characters being sent from Netlinx.

    My problem is that I don't know how to remove completed strings from the buffer for parsing.

    Other devices delimit completed data strings with a carriage return, making it very easy to know when the string is finished.

    Which brings up the question-when does the STRING EVENT trigger, when the first character arrives, or some time thereafter?
  • adimexadimex Junior Member Posts: 21
    The string event is ran when data enters the AMX from the device. The problem with those decks is the data is slow so the string event will run multiple time.

    I first buffer all the data from the JVC, then do bitwise comparaison on all the incoming caracter. If you look at the D5 and D7 response (I think, on top of my head, could be other number), all the bytes and some fixed bits, execute a BAND with a mask to figure out which one is the last byte of the string, then you can use that as a seperator...

    I have written a module in Crustron which I can translate to AMX and post when I get back to the hotel.

    Hopefully this is what you need... :-p
  • gregrgregr Junior Member Posts: 54
    Sounds like you have solved the problem I am experiencing, adimex.
    You are talking about commands which I have never used, tho.
    If you could post the module, that would be great!

    BTW, are some of these devices as cantankerous to control as they seem? I am constantly amazed at the disparity among the device manufacturers when it comes to control strings.

    Now, I need to learn how to use modules...

    Thanks for your help.
  • edgelitocedgelitoc Junior Member Posts: 160
    Recently I just programmed this devices and I have found this problem. Selection of Deck is terrible i have to send first Command Target $FO and put wait command then send $30 for VCR and $38 for DVD. The most interesting part, the customer wants to control all the functions on 2 dvd simultaneously with a single button.
  • ROOROO Junior Member Posts: 46
    JVC SR-1500US - OPTIONS Menu Key

    Hi all,
    The JVC command structure looks similar to the decks above. I haven't found an RS232 code that functions as the OPTIONS key on the remote. Code for Remote data is a "$9F", and "$44" is HDD Drive. The option menu brings up the HDD Delete options for the deck (along with others). I've worked through the list (Trial & Error ) without much luck.

    Does anyone know the OPTIONS key command?

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