Home AMX User Forum NetLinx Studio

Help with McIntosh 861 DVD.

Ok, so this is one of the most unnecessarily complex components I've had to deal with. Even Mac recommends doing RS232 to IR from their pre-amp (which I will probably do for control). I still need to process feedback from the player.

It does send some unsolicited feedback, but I need to send some query commands. I'm can't seem to figure out the checksums it's looking for. Here's from the PDF:
Commands : <STX> <CC> <PC0> <PC1> <PC2> <---------> <PCn> <ETX> <BCCH>
<BCCL>
STX (Start of TeXt) : 02h
CC (Command Code) : Command code
PC (Parameter Code) : Defined for each command
( contents and number of parameters )
ETX (End of TeXt) : 03h
BCC (Block Check Character) :
CC + PC0 + PC1 + PC2 + --------------- + PCn + ETX = XYh
(Each of X and Y is 4 bit long ) X , Y=0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
BCCH ( high-level byte ) = X as converted to an ASCII code
BCCL ( low-level byte ) = Y as converted to an ASCII code

Answers : <STX> <RC> <AC> <PC0> <PC1> <PC2> <--------> <PCn> <ETX> <BCCH> <BCCL>
STX (Start of TeXt) : 02h
RC (Reply Code) : Reply code (=Command code)
AC (Answer Code) : Answer code
PC (Parameter Code) : Defined for each command
( contents and number of parameters )
ETX (End of TeXt) : 03h
BCC (Block Check Character) :
RC +AC + PC0 + PC1 + PC2 + ------------- + PCn + ETX = XYh
(Each of X and Y is 4 bit long) X , Y=0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F
BCCH ( high-level byte ) = X as converted to an ASCII code
BCCL ( low-level byte ) = Y as converted to an ASCII code

As you can see, the answers use the same checksum. Here's an unsolicited feedback with the BCCH & BCCL on the end to help make sense of it:
2,30,20,36,30,3E,3B,3B,30,30,31,30,30,30,30,30,30,30,30,30,30,30,30,3,33,45
2=start
30=reply code
20=answer code
XX-XX=PC codes
3=end of text
33=BCCH
45=BCCL

If someone can help on the checksums I think I can get it. If someone has a full module I'll idol you forever!

Thanks,

Kevin D.

Comments

  • Joe HebertJoe Hebert Posts: 2,159
    shr00m-dew wrote:
    As you can see, the answers use the same checksum. Here's an unsolicited feedback with the BCCH & BCCL on the end to help make sense of it:
    Quote:
    2,30,20,36,30,3E,3B,3B,30,30,31,30,30,30,30,30,30, 30,30,30,30,30,30,3,33,45

    ...If someone can help on the checksums I think I can get it.
    Kevin,

    Get a calculator out and put it into hex mode. Now add up all the numbers (starting with the reply code $30) except for the last two bytes and you should get $43E. Lopping off everything after 8 bits you get $3E. The high byte is $3 and the low byte is $E but those are supposed to be converted to ASCII. So the next to last byte in the response (BCCH) is a $33 which equals ASCII '3' and the last byte in the response (BCCL) is a $45 equals ASCII 'E'.

    Does that help?
  • Doh.. I was including STX in my reverse engineering. I had a total of $440 and couldn't figure out where they got $33,$45.

    Thanks,

    Kevin D.
  • Yup, that did it. Power on works now. Time to get the conversion in a function.

    Thanks again,

    Kevin D.
  • Joe HebertJoe Hebert Posts: 2,159
    Sure thing. Glad to hear you're up and running.
Sign In or Register to comment.