fpga4fun.com

Hello all,

I'm using Xilinx ISE WebPack to develop for and to program Xilinx CPLD and FPGA devices.
From some time ago I work on a HP notebook PC that have no other ports except USB and Firewire. So I cannot use my old parallel low-cost programmer on that machine anymore. I know there are JTAG USB programmers. I want to build my own one myself. Does anybody know for a schematic of such a cable? I google-searched all over the internet, but no success. Here are links to the cables that vendors sell:
http://www.digilentinc.com/Products/Detail.cfm?Prod=JTAG-USB&Nav1=Products&Nav2=Cables for 38$ and
http://www.xilinx.com/xlnx/xebiz/productview.jsp?iLanguageID=1&category=&sGlobalNavPick=PURCHASE&sSecondaryNavPick=&category=/Xilinx+Products/Hardware+and+Cables/Programming+Solutions/Programming+Cables for 150$.
And one more think - does anybody know what is the difference between these two cables? What can do the 150$ one that this for 38$ cannot?

Hi Yassen.
I'm on the same situation, a laptop with nothing to coummunicate outside else than USB!
I thought before to use some USB to serial/parallel port IC's to make a parallel port for my laptop to use in FPGA or microcontroller programmig but i dont have any idea about the complexity of this.
The Digilet Cable seems to build on such this idea, you can see the place of ic onder the black cover.
Another problem may be driver softwares for windows to recognize the cable.
anyway, i'm searching for a usb jtag cable too, and once i found anything useful, will call you. you please call me if you found anything.

Hi, minimos,

Thank you for your answer
I wonder how it can be so difficult circuit... I can find no where description of the cable. I know that it is a bit complex to build a USB cable than to build the simplest one - the Parallel, but nowadays there are less and less computers with LPT on it and all PCs have USB. But I also know that not every USB-to-LPT converter works fine, even for printers. This USB programmer should be very strange thing...

I tried the Digilent cable and here's what I found:

The good:
* Cheap
* Configure Xilinx's FPGAs and program Xilinx's PROMs
* Has some capability to send data to your FPGA

The bad:
* Not compatible with Xilinx's iMPACT (and probably not compatible with Chipscope either)
* Ignores any non Xilinx device
* Closed USB protocol (you can't write your own JTAG software using this cable)

Using a .bit file (to program an FPGA), I measured a speed of 90KB/s (approx).

Thank you, Site Admin,

This is very valuable information for me.
Hmmm, I like "The good" as I intend to use the programmer just for Xilinx devices, but "The bad"... What means "Not compatible with Xilinx's iMPACT" ? As I am relatively new to this field (programmable logic devices and hdl tools) , at present I know how to program my boards just through the Project Navigator / iMPACT (or iMPACT separately) . I thought I could use USB JTAG Programmer as full replacement of Parallel cable...
What other methods of programming exist ? Any starting point on that ? Will I have some troubles if I purchase (...or made...) USB JTAG Programmer ? What do you use on PCs that have no other but USB port(s) ?

Cheers,
Yassen

P.S. You have build a very nice site! Congratulations! I have discovered it soon and I'm impressed by the idea for it and by all the good stuff inside

iMPACT doesn't "see" the cable. So instead of iMPACT, they provide their own utility. Also iMPACT still needs to be used in some cases (to build svf file, or something like that, not tried yet, as their spec isn't too clear). And then their utility has to be used. So it's not as convenient as iMPACT. But for the price, can't complaint too much. Check the cable spec for more details on Agilent website.

USB cables are nice, nothing to worry.

A little update.

I tried the Digilent cable on a Spartan device and had no problem. Now I'm trying with a Virtex 2 PRO device, the cable "sees" the device in the chain but refuses to program it (reports an error "IDCODE is wrong"). Likely a software bug. I emailed Digilent a week ago... but no response so far. Not great for me since I actually bought the cable specificaly for the Virtex 2 PRO device.

Jean,

What does it mean "has some capabilities to send data" in the description of the digilent usb cable.

second question: Is Your sware able to communicate with avnet spartan3e board; they also use fx2 chip. I am specially interested in data communication because it doesn't work in their examples.

I didn't investigate their data capability but from what I understand, you can send data to the FPGA through JTAG. If that's the same speed as configuration, you should get something like 0.7Mbits/s (since I measured 90KB/s with my stopwatch).

I also got a board with Spartan 3e (not sure you are speaking of the same) with an FX2. But sadly they don't give any info about the FX2 (they even remove the matching pages from the schematic). So I don't believe the USB is usable for your own usage.

The avnet board has all the shematics, but data transfer doesn't work with their sware.


The digilent s3e500 board has a version of xilinx platform cable integrated. Shematic of that part is missing, but the interface works as intended; for debugging and for chipscope. Data transfer is possible but with only 12 Mbit/sec.

hi,

- after upgrade JTAG-USB by Digilent Software i'll broken eeprom software.
- pls send me VID and PID for this JTAG USB with SPI.

thx.