A list of possible design revisions for subsequent I2C and SPI Shield boards…

1. Done 18-AUG-2014 Rev: Move the temp sensor from being located over the ATmega328
2. Done 18-AUG-2014 Rev: Spread the LEDs out a bit.
3. Done 18-AUG-2014 Rev: Move all bottom side components top side so small batch assembly houses can build it.
4. Done 19-AUG-2014 Rev: Connect the buttons to available pins so that they can be used long term as well. Three hardware-debounced buttons would be valuable.
5. Done 19-AUG-2014 Rev: Make the 74HC595 available in all sketches so that bitwise operations can be visualized on the LED array.
6. Done 18-AUG-2014 Rev: Modify battery backup circuit for the MCP7940N to match the appnote.
7. Done 19-AUG-2014 Fix: Increase the pad size for the SOIC16 footprint, see if the SOIC8 is a good guide.
8. Done 18-AUG-2014 Fix: Add test points / pads / header
9. Done 19-AUG-2014 Fix: Change MCP3008 bypass cap to 1uF, as per datasheet.
10. Done 18-AUG-2014 Rev: Move the VREF silk screen so its more visible.
11. Rejected Rev: Consider putting an LDR or pot on the board with a jumper to give something to measure with the ADC out of the box
12. Done 18-AUG-2014 Fix: Change signal at the U4 level shifter, currently MOSI and SCLK are mixed – A1 -> B2 A2 -> B1.
13. Done 08-NOV-2014 Rev: Change the GND pad for the battery holder to a larger physical space to ensure good contact with the battery.
14. Rejected Rev: Remove Test Points.
15. Done 08-NOV-2014 Rev: Remove 0Ω jumper resistors.
16. Done 09-NOV-2014Rev: Add a pullup resistor for the Temperature Sensor Alarm pin.
17. Done 09-NOV-2014Rev: Add a jumper to allow control of the shift register OE pin.
18. Done 09-NOV-2014Rev: Add 10uF cap at +5V

After including the necessary design revisions, this is the final production version for the I2C and SPI Education Shield v1.