Actually I have been hacking on the shield design some more and will probably order myself a few more boards to populate...
Currently the board design looks like:
DipTrace-PCB---Arduino-Mega.jpg [ 76.17 KiB | Viewed 112 times ]
The main differences in this version include:
a) bottom left of board is cut out some, such that the lip of power connector on the Due and probably new megas will be outside the board, which will allow the board to get lower. Hopefully help some with stackable header issues.
b) I Removed 4 IO pins and their power connections from the board to make room... Figured I have plenty.
c) Fixed power connection. That is I screwed up and the VIOREF pin was not connected to the circuit that needed it.
d) Changed Power stackable header to 8 pins, so I don't have to cut one down to 7.
e) Added 2 more pins on the digital pins header, such that I picked up (at least for jumpers) the IO pins associated with 2nd I2C on Due
f (probably most important) ) Changed how I did voltage conversion for XBee and other Serial ports. I added an 74HC244A chip to do voltage conversion. Same chip that is used in the Parallax XBee adapter. It has 2 groups of 4 pin buffer/conversion. So I used this for the 4 TX/RX lines. So I believe that this should allow me to plug in XBEE to either 3.3v or 5v system. Likewise I now should be able to plug in SSC-32 connector to TTL and have it handle the voltage conversions... I am passing 3.3v to VDD on the chip, so I believe the RX and TX will be high on 3.3v on either voltages which I don't think will create a problem.
g) ISP connector - I had this on earlier boards, but if you use it with the male pins sticking up, it would interfere with plugging in an xbee. So I plan to use standard breakable header pins sticking down from board into ISP connecor on main board. I then put in a 4 pin connector near where I have the USART connections. Note on Due this connector is not work as an ISP but is only used for SPI.
That's all for now.