This project is actually a revisit of my old Wiseduino, with the same goal: an Arduino-compatible with on-board Real Time Clock, and some extras (in this case, an XBee-like device). I renamed it "wsduino", although the pronunciation should remain the same :)

I redesigned wsduino mainly for the Axiris IV3 clock (see photos), whose enclosure allows for only 2 boards (Arduino + IV3 shield), with openings for power socket, USB, and no accessible buttons. Essentially, wsduino saves you an extra shield, which would have hosted the RTC (+backup battery).

wsduino comes as a kit, which includes (see photo):

• PCB
• ATmega328 processor with bootloader for 16MHz
• ATmega328 processor with bootloader for 8MHz
• 28-pin socket
• 16MHz crystal
• 2 x 22pF capacitor
• power jack
• 7805 voltage regulator
• 1N4001 diode
• USB miniB socket
• DS3231 RTC (SMD)
• A1117 3V3 regulator (SMD)
• CR1220 battery + holder
• 4 x 10k resistor
• 4k7 resistor
• 3 x 100nF capacitor
• 47uF/25V capacitor (C2)
• 47uF/16V capacitor (C1)
• 470uF/10V capacitor (C7)
• 2 x 10-pin 2mm female header for XBee
• 40-pin 0.1" female header
• 3-pin header + jumper (selection of power source)

An FTDI breakout is required to upload sketches. The orientation of the FTDI connector is marked on the top silkscreen (but can be used on either side) with "BLK" and "GRN".

Assembling the kit is quite trivial, except maybe for the 2 SMD parts (DS3231 RTC and A1117 voltage regulator), which must be soldered on the bottom of the PCB. Pay special attention to the orientation of DS3231.

A minimal wsduino is shown in the last 2 photos. The processor runs on the internal oscillator at 8MHz, powered through the USB miniB connector. The RTC and 3V3 regulator are soldered on the bottom.

Solder the crystal (and the 22pF capacitors) ONLY if you plan to run your wsduino at 16MHz (in this case use the ATmega328 with bootloader for 16MHz).

Soldering the power jack, the 7805 and the diode are optional as well. If you plan to power your wsduino from USB (through the USB mini B connector), you don't need to solder the mentioned components.

The 3V3 regulator (soldered on the bottom) is used to power the XBee (or XBee-footprinted, like GPSBee, BTBee etc) module. If you don't use any, you can leave it out (unless it is required by any of your shields that you will plug into wsduino).

Note: Although the silkscreen says 100uF for C1 and C2, the capacitors included may differ (depending on the stock I have). The rule is this: C2 must be the highest voltage (e.g. 16-25V), then C1 should be the middle voltage (10-16V). C7 is always 470uF/10V, filtering 3V3 (takes some of the initial load from the XBee when the board is powered up). In case C1 you received is higher than the header, you need to bend its terminals and solder it on its side (see the photos).