Wednesday, April 15, 2009

One step at a time...

So I got the sparkfun spartan3e breakout board and parport programmer today. My custom board should arrive tomorrow (it plugs into the breakout board). In the meantime I've been sanding down the female headers so they all fit on the board. The idea is then I can plug stuff into the breakout board and easily detach them so I can reuse the breakout board for other projects later.

I soldered in one side of the header and did a little scrolling led test which you can see below:

I guess you can't really tell from the picture, but each led lights one at a time, scrolling across. I thought it was kind of interesting that sparkfun fails to mention in the product page that this board actually comes with an oscillator (I think 50MHz?). Very handy! It's in their schematic but it's not clearly labeled as an oscillator, just an inconspicuous random box with an enable signal and an "output" signal. Also they supply some fpga code to help flash the on-board PROM but it's targetted at a different fpga (not the one they put on the board). After I finish sanding/soldering the headers, I might post on the forum and ask about that.

In reality you shouldn't even need that stuff, since the Xilinx iMPACT software should be able to flash the PROM over jtag. I'll have to remember to test that soon.

EDIT: I was able to erase/blankcheck the prom over jtag, so I think it works. For instructions, see: xapp974.pdf
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5 comments:

  1. Jose TorresApril 15, 2009 at 11:22 PM

    Cool project!
    Why did you decide to go with Xilinx from Altera?

    ReplyDelete
  2. scottjgApril 16, 2009 at 12:53 AM

    jose! so glad you checked out my blog. your gb carts were really the inspiration for this.

    The main reason I switched to the Xilinx Spartan-3e is because it has internal clamping diodes that are always enabled (even before you load the bitstream). This means that I can just put some resistors in series with the 5v signals and no other external level conversion is necessary. The Altera CycloneII allows you to enable clamping diodes (for pci) but they aren't enabled before configuration.

    As a side-note the Xilinx software is TERRIBLE compared to the Altera software, but oh well... I guess.

    ReplyDelete
  3. optixxApril 21, 2009 at 4:25 AM

    Hey, how is the new fpga coming down? We are a little stuck.
    Can't even get any commerical lorom 2mbit type 0 running. Only homebrew. Was thinking if you could give us an advice how you handle RESET / IRQ and CS Lines on startup.
    I think we do something wrong with that or we have a address flipping bug in our poc sram interface...
    Cheers Optixx

    ReplyDelete
  4. scottjgApril 21, 2009 at 10:26 PM

    @optixx I shot you an e-mail, but the short answer is that I don't drive (or even read input) from any of those cart pins.

    ReplyDelete
  5. Alan GJune 19, 2009 at 9:27 AM

    Hey,
    would you have a IDE project with the test code still? im struggling to get my sparkfun board going. I'm thinking its a problem with the jtag port on the fpga

    ReplyDelete

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