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1  Development / Other Hardware Development / Teensy++ and centepede shield on: October 28, 2012, 02:34:45 pm
I want to use the Teensy++ 2 to run a chessboard with 64 LEDS and 64 reed switches. The centepede shield: http://docs.macetech.com/doku.php/centipede_shield  seems an ideal solution, especially as you can link two to address 128. it It uses the Wire I2C interface on analog pins 4 and 5 to provide 64 general purpose I/O pins. (x2) so I get massive addressing for only 2 pins with the added bonus that you connect using a ribbon cable and it has built in resistors.

 It is designed to stack on a standard uno type board, however I want to use the Teensy because that can communicate using serial USB and keyboard at the same time.

So my question is, which pins represent the "Wire I2C interface on analog pins 4 and 5 " and can i just solder connections of two centipedes in a daisy chain arrangement?

Any other observations welcome.

Max
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2  Using Arduino / LEDs and Multiplexing / Re: Reading chess board with reed switches on: October 04, 2012, 03:58:44 pm
I am trying to build a reed switch based chess board too. The scanning matrix aproach seems the most elegent solution.
 However there is another way. (I think, I am new to Arduinio and may have missed something) Have you seen the Centipede Shield? See http://macetech.com/store/index.php?main_page=product_info&products_id=23. This is a shield with 64 pins that links to the Arduino boad using only a few pins. It also uses ribbon style connectors so that would simplify wiring. I assume you would wire one end of all the reed switches to ground and the other 64 to ribbon ends.
I assume that this would simplify processing as you would just need to scan for a change of state. (Would you still need a resistor or diode on the Reeds?)

If you looked for two move combinations, ie the "From" move followed by the "To" move, then the first move would always be a change of state from closed (Occupied square) to open (Piece gone). The second move would be to an empty square (Open to closed) unless its a capute then its to a closed and you can assume you will get a combination as the old piece is first lifted (closed to open) and the replaced (Open to closed). But all are on the same square and the final state is closed (occupied).

Any practical observations most welcome.

Max
3  Using Arduino / Project Guidance / Re: Board with placement identification & piece recognition (for game or something) on: October 04, 2012, 03:22:44 pm
Hi,

The problem you desribe is the classic chess piece identification task. Most sensory boards just detect the precence or abscence of a piece and infer its value from a know startiong position. eg the Novag Citrine which uses reed switches. The leading reliable chess piece identification system is the DGT board, which uses a patented process: see: http://www.chesscomputeruk.com/1999_-_DGT_Tasc_Piece_Recognition.pdf  . The technology is Resonance coils of different types located in the pieces. A non trivial technology. The DGT board & pieces retail for around $1000. RFID is unlikely to work for the reasins given elsewhere. It is really an Identification technology. In theory you could use triangulation based on signal strength from 3 RFID readers, but I don't know of a way to force the readers to sequentially read all pieces in range. Plus the readers interfer with each other. There are "RFID Radar" devices out there that do this, but they use a large array of readers.
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