> The actual Huffman decode algorithm is actually pretty simple.
> You treat the
> the compressed message as a sequence of bits and walk to the left or right
> in the tree for each one. As soon as your walk encounters a link that has
> the high bit on then you have found the character to output.
>
  Yes, simple it is. Reconstructing and storing the tree is the tough part.
  Another alternative would be to use  6 bits to store the symbols instead
of
  the usual 8 bits. But the savings are very minimal and probably its not
worth
  the effort.

  The method I use is very simple. I use a table of strings in the program
memory
  (using the dw directive to include packed ascii). Using 2 retlw tables, I
get the
  16 bit offset to the null terminated string in the program memory of the
PIC.
  AFAIK, This is the simplest method to use. A kind of a dictionary
optimized for
  the most frequently used technical terms (Its used in a UPS).

  I also made a simple stack to store all the RXed bytes from the USART. The
recieve
  ISR keeps pushing all the recieved bytes into the stack.As soon as a '\n'
is recieved,
  The ISR raises a flag bit to let the processing code in the main loop take
over.
  I have a few simple subroutines to match strings(case sensitive!), numbers
(decimal only) etc.
  With this, I  could develop simple commands like.

        SET FREQUENCY TO 50
        GET MOSFET TEMPERATURE etc.

  If a string is not recognized, it transmits "Unrecognized statement"

  I guess with simple string parsing functions, It is possible to make a
simple BOT
  having trivial intelligence with a 16f877. A simple idiot with trivial
intelligence
  lower than a rat. Atleast a rat learns but anything like this will be
stuck with
  simple programmed intelligence. Anyway, the next HAL won't be made out of
PICs ;-)

  [Ok I'm sorry, I've rolled really off topic from Huffman encoding to AI in
PICs.]

Reagrds,

Jeethu Rao

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