"Run destination iOS Device is not valid" for iPod Touch running 3.1.3 with XCode 4

I'm trying to test my application against a friend's old iPod touch running iOS 3.1.3.

I have XCode 4 and receive this error message when trying to run the application:

The run destination iOS Device is not valid for Running the scheme 'MyApp'.

The scheme 'MyApp' contains no buildables that can be built for the architectures supported by the run destination iOS Device. Make sure your targets build for architectures compatible with the run destination iOS Device.

I have set the deployment targ开发者_开发问答et to iOS 3.1.3. What else do I need to do in XCode 4 to build and test the app on this old iPod touch?

I am using the "standard" build architecture, not optimised.

I solved this by Autocreating schemes (Scheme > Manage schemes > Autocreate schemes) and then selecting the iPod Touch instead of "iOS Device" which had appeared in the schemes. D'oh!

In my Target->General, I selected Device "iPad" and was trying to run in an iPhone simulator. I just changed the Device option to universal (which was alright for me) and then run again. It solved my problem.