Typical smartphone keyboards are modal. There is usually a basic QWERTY/Basic punctuation keyboard by default that can be switched to numeric/extended punctuation mode.
This works reasonably well until we get to the issue of entering a Canadian postal code of the form "L2L 2L2". (Casing and the space are unimportant.) In order to enter a code, the user has to toggle the keyboard mode 5 times, making the input extremely clicky.
One alternative would be to provide 6 option lists, (A-Z, 0-9, A-Z ...), but the alpha lists would be quite long, and might not fit on the screen.
Has anyone looked at this problem, and what alternatives did you come up with?