Arduino), especially if you're design is well pipelined. You can build a rudimentary data acquisition and control system using a microcontroller (e.g. Last I knew, Chipscope was not free, and that is why my hobby projects always use Altera FPGAs. Quartus II should give you a free license for SignalTap as long as you agreed to share anonymous statistics with them.
HOW TO USE ALTERA QUARTUS II CODE
Both Altera (with SignalTap) and Xilinx (with Chipscope) provide both the FPGA code and the GUI to drive it via the JTAG port. Another possibility is to log the debug data inside the FPGA in a block RAM and read it out later. This is extremely cheap in terms of FPGA resources. Typically to debug an FPGA you bring out debug pins and look at them with an oscilloscope or logic analyzer (even an inexpensive one like the Saleae logic). You could implement (or find an existing implementation, called "IP" in HDL land) a UART and print out data yourself, but this is a very complex and costly (in terms of FPGA area) exercise in an FPGA. So the scripting parts that actually affect synthesis can be thought of more like metaprogramming. If you put synthesizable code inside that loop it will be replicated by the loop (creating a whole bunch of parallel FPGA paths, one for every pass through the loop).
If you write a for loop in a simulator it will loop like any other programming language. There is some slight overlap, but even that does not work how you might expect. The constructs used for scripting simply have no effect when the code goes through synthesis to be used in an FPGA. They often start with part 2 (which includes things like $display) because newcomers are trying things in a simulator.
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