Input comes in from the board via the matrix of Hall effect sensors. These are multiplexed in order to minimize power consumption. Multiplexing is made possible by the 3 to 8 decoder. The PIC is programmed to have the decoder innervate one row of sensors at a time. Once a row is innervated, the shift register relays any high signals in that row (signifying the placement of a magnet above the sensor) to the Pic. The Pic then decodes this message to update the position of the board in its memory, and loops through the remaining rows.

Output happens in much the same way. The Pic is programmed to have the decoder innervate one row of LEDs at a time. Once the row is innervated, the shift register is loaded with that rows data in order to sink current on the lines connected to those LEDs that should be on. The decoder/shift register system loops through the remaining rows.

Not included in this diagram is the connection to the Cobox Micro. The chip displayed here, the 16F84 has run out of i/o pins, and it’s necessary to move to a giant like the 18f452 – more on that next time.

Tech overview
A Pic microcontroller handles all the sensing and display on each board. The networking on each board is handled by the Cobox Micro, which receives serial data from the Pic and translates it into a TCP stream sent to a Java chat server. The Java chat server relays that message to the other board (and any observers).

Sensors
The sensing of moves relies on Hall Effect sensors embedded underneath the surface of the board. Each stone contains a small magnet that activates the Hall sensor when placed on the board. Each activated sensor feeds into a parallel-in, serial-out 8-bit shift register. Due to the nature of the game, only one sensor will be activated per move.

Display
The display of the opponent’s moves results from an inductive coil also embedded underneath the surface of the board at each intersection. Also in each stone is a coil and LED in series that makes the stone light up when placed above the activated inductive coil in the board. Power to the inductive coils is fed in a row-column csanning matrix. A series of 3 to 8 demultiplexers send power to one row at a time. Serial-in to parallel-out 8-bit shift registers control which coils in a given row are active.

My midterm project is a networked go board. This project has personal use to me since when I play go, it is usually online. I rarely have the opportunity to be in the same room with another go player for long enough to have a good game. The go board is an important part of the ritualistic quality of the game – something that is notably missing in the online versions.

The Networked Go Board addresses this problem by providing a standard simple physical go board networked to another similar go board at a remote location. Players make moves as they would in a normal game – by placing stones on the board. These stone placements are represented on the opponent’s board via lit LEDs. The opponent may then place the player’s stones over the lit LEDs and make his or her own move in the same fashion.