quinta-feira, 6 de maio de 2010

Inside the Sapphire II (By Richard Tervo)

All credits of material is to Mr. Richard Tervo
The Novag Sapphire II is a powerful portable chess computer. It features an external connector to communicate with a 'smart' chess board, or with a PC. Specifications for the serial communications port are not available from Novag but, fortunately, the critical information can be found in other ways... The Sapphire II protocol uses standard serial port parameters to send and receive 8-bit ASCII at 9600 bits per second. It remains to wire a special connector to attach to the Sapphire II.

Secrets Revealed...

Power Supply Connector

While the case is open, it is a good time to note that the power supply connector is wired "center negative". An inexpensive 9 VDC adapter with this same connector will power the Sapphire II and save a lot of batteries.

A Different kind of RJ-11

The serial plug resembles a standard RJ-11 telephone jack, but the Sapphire connector requires six pins. Most RJ-11 plugs are six pins wide but only the middle four pins (or middle two pins) are present for use with a telephone line. In fact, only four pins actually have wires attached within the Sapphire, but they are not the center four pins, so a full six-pin RJ-11 plug is required.

If a six-wire telephone extension cord can be found, it can serve to connect to this serial port. (Note that most telephone extension cords are 2- or 4-wire and would be unsuitable.)

Identifying the Connections

Let the six pins be numbered 123456, as seen from the outside of the Sapphire II. The diagram below describes each of the pins and shows the cable necessary to connect the Sapphire II to a standard (COM) port.

What's the Connection?

The serial connection is compatible with a standard serial port, but finding the pinout for this plug is another matter. The mystery can be solved by opening the Sapphire II to see what is inside...

Sapphire II Serial Communications Port
Pin 1 = ground
Pin 2 = high (+4V) when power is on
Pin 3 = TX data out
Pin 4 = unused
Pin 5 = RX data in
Pin 6 = unused

IBM-PC Serial Communications Port
(Pins as numbered on the connector)
Pin 8 = CTS
Pin 5 = ground
Pin 3 = TX data out
Pin 2 = RX data in

Testing the Connection

Whenever the red NG button is pressed on the Sapphire II, the text message "New Game\n" is transmitted from its Serial Port. This data stream may be used to test a connection between the Sapphire II and another serial port.

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