Jeremy W. Langston

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DE2-70 SOPC Tutorial Introduction – A list of problems…and solutions!

I recently purchased a Terasic DE2-70 Cyclone II development board.  The makers have two prices:  $599 commercial and $349 academic.  If you’re a college student, the academic price is still too much.  After I got a job, made some money, and saved up, I sent the Taiwanese company Terasic a little email.  I told them I recently graduated and wanted to get the academic price, stating that I would be using it for personal learning, etc.  They were more than happy to offer the discount, so I’m now the proud owner of a DE2-70.  (By the way, they ship from Taiwan – viz. $40 shipping from the other side of the world.)

Well, having gone through Altera’s “Introduction to the Altera SOPC Builder Using VHDL Design” to remember how to use the software, I found multiple problems with the tutorial as it is.  I hope that listing the solutions here will help people in the same situation.  Some of these issues are obvious, and some are a bit more subtle.

I am using Quartus II 7.2 and  NiosII 7.2.

  1. In Step 1: “In your project, choose the EP2C35F672C6 chip as the target device, because this is the FPGA on the DE2 board”. Well, the DE2-70 uses a different chip.  Choose the EP2C70F896C6.  This can be verified by simply looking at the text printed on the FPGA.
  2. In Step 1: “You can choose a different directory or project name, but be aware that the SOPC Builder software does not permit the use of spaces in file names”. This is true and I just wanted to make it obvious that you can’t have a space *anywhere* in the pathname.  For example, you would have problems in SOPC  Builder if your project was in “C:\Program Files\…” since that path contains a space.
  3. In Step 6: “In the On-Chip Memory Configuration Wizard window, shown in Figure 8, set the memory width to 32 bits and the total memory size to 4 Kbytes”. As I’ll be getting to shortly, the 4kB is not enough for the NiosII project.  Crank it up to 64kB for plenty of breathing room.
  4. In Step 7: The PIO is under Peripherals -> Microcontroller Peripherals -> PIO (Parallel I/O).
  5. In Step 9: The JTAG UART is under Interface Protocols -> Serial -> JTAG UART.
  6. After Step 11: Write down the base addresses of the PIOs after auto-assigning the addresses.  These will be needed for NiosII, as they are treated as memory-mapped I/O.
  7. Before Step 12: There are a couple “To Do”‘s in the message window of SOPC Builder about the NiosII CPU that need to be addressed:  the reset and exception vectors.  Double-click the NiosII component you instantiated to open up the properties window you were at before.  Now that you have on-chip memory instantiated, click on the Reset Vector and Exception Vector Memory drop-down boxes and select the name of your memory (e.g. “onchip_mem”).  Leave the offsets the way they are (0x0 and 0x20).  Don’t worry about the “Warning: Switches: PIO inputs are not hardwired in test bench. Undefined values will be read from PIO inputs during simulation.”, this tutorial doesn’t do any test benches.
  8. Importing DE2_70_pin_assignments.csv.  This comma-separated file is located on the DE2-70 CD included with the kit, and it can also be found on the internets.  Mmm, google.  The naming convention for this Altera-supplied file changed from DE2 to DE2-70.  Open it and take a look.  There are now lower-case ‘i’s and ‘o’s before many of the hard-wired signals denoting them as input and output.  Remember this!  The HDL code needs to change reflecting this.  Otherwise the .csv needs changing, but I don’t suggest it.  Here’s my resulting code (remember, the port names may be different for your SOPC component):
    • LIBRARY ieee;
      USE ieee.std_logic_1164.all;
      USE ieee.std_logic_arith.all;
      USE ieee.std_logic_unsigned.all;

      ENTITY lights IS
      PORT (
      iSW        : IN    STD_LOGIC_VECTOR(7 DOWNTO 0);
      iKEY    : IN    STD_LOGIC_VECTOR(0 DOWNTO 0);
      iCLK_50 : IN    STD_LOGIC;
      oLEDG    : OUT    STD_LOGIC_VECTOR(7 DOWNTO 0)
      );
      END lights;

      ARCHITECTURE Structure OF lights IS
      COMPONENT nios_system is
      port (
      — 1) global signals:
      signal clk : IN STD_LOGIC;
      signal reset_n : IN STD_LOGIC;

      — the_LEDs
      signal out_port_from_the_LEDs : OUT STD_LOGIC_VECTOR (7 DOWNTO 0);

      — the_Switches
      signal in_port_to_the_Switches : IN STD_LOGIC_VECTOR (7 DOWNTO 0)
      );
      END COMPONENT;

      BEGIN
      NiosII:        nios_system PORT MAP(iCLK_50, iKEY(0), oLEDG, iSW);
      END Structure;

  9. Before Section 3.2: If you’ve tried to do a full compilation at this point, you will probably see an unexpected error:
    • Error: Can’t place pins assigned to pin location Pin_AD25 (IOC_X95_Y2_N1)
      Info: Pin iSW[7] is assigned to pin location Pin_AD25 (IOC_X95_Y2_N1)
      Info: Pin ~LVDS195p/nCEO~ is assigned to pin location Pin_AD25 (IOC_X95_Y2_N1)
      Error: Can’t fit design in device
      Error: Quartus II Fitter was unsuccessful. 2 errors, 3 warnings
      Info: Allocated 215 megabytes of memory during processing
      Error: Processing ended: Sun Oct 18 19:11:13 2009
      Error: Elapsed time: 00:00:03
      Error: Quartus II Full Compilation was unsuccessful. 2 errors, 152 warnings
    • Here is the fix:
      • In Quartus-II select menu Assignments>Device…
      • Select button “Device and Pin Options…
      • Select the tab “Dual-Purpose Pins”
      • Under the list of “Dual-purpose pins:” change the “Value” property of nCEO to “Use as regular I/O”.
      • Click OK
  10. After Section 3.2:  If you are using the Web edition or didn’t buy the full license for the Altera IP, you probably got a pop-up window after programming the device stating “OpenCore Plus Status Click Cancel to stop using OpenCore Plus IP.  Time remaining:  unlimited”.  Do not close this window if you intend on using the NiosII IDE to run on the hardware.  Just leave the window up and close when you are done, or have a problem with Quartus or SOPC Builder.
  11. I skipped over the Assembly programming section because this tutorial already gave me a headache.  I’m not a masochist.
  12. In Section 4.2: When you create a new project, create it in the following way:  File -> New -> Project… and select “Nios II C/C++ Application”.  Also, use the Hello World template.  It sets everything up for you, gives you printf functionality to the console, but takes up a bit more space.
  13. lights.c:  Here’s what I have in my file.  Again, it might be a bit different for the base addresses.
    • #include <stdio.h>
      #define Switches (volatile char*) 0x21000
      #define LEDs (char*) 0x21010

      int main()
      {
      printf(“Hello from Nios II!\n”);
      while (1){
      *LEDs = *Switches;
      }
      return 0;
      }

  14. After all of that is done, you right-click on your project in NiosII IDE (e.g. hello_world_0) and click “Run As -> Nios II Hardware”.
  15. Done!  You can now move the switches (SW7 – 0) and see the LEDG7-0 change.  You can also reset the CPU using KEY0.

I know how frustrating it can be trying to learn something when the tutorial is wrong.  Hope this helps!

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