Wise Clock 4

The new Wise Clock 4 board has two main improvements over Wise Clock 3:

• support for the XBee family of wireless RF modules (XBee, XBee Pro, XBee Wi-Fi, and the similar foot-printed Roving Networks WiFly RN-XV);
• ability to easily connect a second display; this is achieved by moving the power connector on the "right" side, plus bringing the extension display connector closer to the bottom of the board.

Wise Clock 4 is "almost" compatible with Wise Clock 3. To run the existing sketch on Wise Clock 4, two changes are required:

• Plus button is now on D3 (D2 is now designated for interrupts from RTC);
• D15 is now connected to the CS line of the display, replacing D11, which is now used for communication with the Xbee module.

As can be noticed from the photos, a few more components are in SMD package (necessary to keep the size of the board to a minimum, to fit in the back of the 3216 display):

• the level shifting buffer 74HC125;
• three optional LEDs: 2 for the XBee communication lines, one for power;
• the 3V3 voltage regulator MIC5219, capable of providing 500mA.

Updated Nov 26, 2011
The schematic, pictured below, can be downloaded from here (Eagle file).

The board layout, shown below, can be downloaded from here.