When you design Arduino shields, do you typically target a specific Arduino board (e.g. Uno) or try to make it compatible with as many boards as possible? e.g. Uno, Leonardo, Mega2560...
I'm also curious about the number of people with each type of Arduino board, i.e. market share, if anyone has that info.
Well, because of that need, my own need also, I've designed already two multi-platform shields. I've decided then to made them available.
One aimed for both Chipkit Max32 and Arduino Mega, and other for Arduino Mega and Arduino Due.
Both have diferent pinouts for each platform to have the best performance possible.
You may see them in the next links.
Mega / DUEhttp://www.aqualedsource.com/shop/product_info.php?products_id=32
And Mega / Chipkithttp://www.aqualedsource.com/shop/product_info.php?products_id=30
They are designed to allow easy connection to the boards, while allowing a start-up platform with human interface, for that, you just need to buy a TFT with Touchscreen.
This is the base platform for the aquarium controller I'm building!
I think that trying to have multi-platform is the key to save some money later. You never know if your own need will rise and need to move to a better platform like Due for example.