Help with McIntosh 861 DVD.

shr00m-dew

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.

Joe Hebert

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?

shr00m-dew

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.

shr00m-dew

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

Thanks again,

Kevin D.

Joe Hebert

Sure thing. Glad to hear you're up and running.