This is a very common error that usually has a very silly cause but can make you loose a lot of time. Here is a short checklist of some possible solutions to the problem.
Note that this is NOT A COMPLETE LIST! Feel free to add points if you think it might help
Qsys and Quartus:
- did you run the .tcl script?
- reset signals are well connected?
- did you set the top-level file in its right-click menu?
- when programming the FPGA make sure the selected device is "5CSEMA5F31"
ECLIPSE:
- did you recreate the project BSP after modifying the hardware?
- did you select the right file to upload? (try right-clicking on the project name and run from the drop-down menu)
- are you running the right project corresponding to the programmed softcore?
- if nothing worked, did you try restarting Eclipse?
- Under "Run configurations":
- ignore mismatched system ID is checked?
- ignore mismatched system timestamp is checked?
- did you press "refresh connections" ?
Hope it helps!
