Suggestion for the Arduino DUE and Mega 2650 The addition of 0603 size SMD pads on the bottom of the board to break out the pins that are not used on the board would be great, and would allow backpack shields to make a non soldered connection to the extra pins, hence allowing them to be used in a project, or just be broken out would be really great. In particular, the DUE and it's massive ARM could really benefit from this, as I'm pretty sure that it has well over 53 I/O pins.
backpack shields to make a non soldered connection to the extra pins
How would you do that reliably without using pogo pins?
0603 are quite user un-friendly. I can still (barely) solder 0603, but I don't like it at all. If 0805 or 1206 would work why not use these?
To clarify, I was kind of thinking about having a grid of 0603 size, or whatever size pads on the bottom of the board just so that a backpack PCB with some sort of connectors on it could make a connection with the Arduino board, and hence use the extra I/O that doesn't come through the pins of the board. I can see the potential issues, and how it would be difficult without using pogo pins. I guess you could also do it by using a really tight pitch ribbon cable connector on the board, a bit like the ones used to connect LCDs to the circuit boards in Cameras, etc. I guess you could also use springy connectors like those used to make connections with SIM cards in phones.
Doesn't have to be 0603, in fact, 0805 would be better, but having a look at the bottom of the board, there isn't that much space left.
I think you would have to use the mounting holes in the board to make a reliable connection.
Much better, creating such interface with the external memory pins available in the back. That could allow several shields to be connected in a rack kind of setup.
I love that idea. Stackable memory bus and unused pins broken out somewhere could be very useful. Just because 0603 is harder to use than holes or headers is not a valid argument to make the pins completely inaccessible. Pogo pins are one solution, headers can be hand soldered to 0603 pads on .1" centers. There are also lower profile spring tension connectors like the ones used on the Atmel STK-600. In fact, if the pads were laid out in the same pattern as a STK600 routing card, and appropriately located holes drilled, the new arduinos could connect directly to the STK600 giving immediate access to all ports, USB, Serial, various programming interfaces, power supply, switches, leds... Dustin Maki