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Open protocol USB JTAG cable

Hi everybody,

I'm going to build a USB JTAG cable and I don't know what protocol should I use for communication. The only cable I can fully implement this time is the Digilent USB cable... (according to the code of Zoltan Csizmadia's cable server project) I was trying to reverse engineer Xilinx's USB Platform cable protocol, but after a point I gave up. (Mostly becouse the firmware of the cable is shipped with the PC software, so they can easily modify the protocol in the new version of ISE)

So, some questions: Is Digilent's protocol free to implement in my device?

Is there any cable with open protocol? (with a GPL like license) If exists an open protocol cable, is this well supported by applications?

Thanks, goss

Reply to
goss
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Checkout JTAGkey and JTAGkey-Tiny from

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. Amontec will provide the jtagkey.dll very soon! But you can still use the OpenOCD JTAG server, and it is GPL and fully supporting the JTAGkey products. Note the JTAGkey products are based on FTDI FT2232!

Best regards, LOL

Reply to
Amontec, Larry

I've implemented the whole Digilent USB protocol and already working in cblsrv-0.2 (with Impact). When I have some time, I will upload the latest version to sourceforge.net.

Zoltan

goss wrote:

Reply to
zcsizmadia

Sorry, I misunderstood the question :)

If you want to use it from cblsrv (using Impact), I 'd make the protocol very similar to the cblsrv protocol. One of the problem with Digilent protocol is it is not very efficient when you are doing a lot of short Shift-IR, Shift-DR operations. That is why reading or writing a platform flash is much slower with Digilent-USB than with Parallell III cable. Of course you should implement the very raw access to JTAG pins as well, but for performance reasons I 'd create some higher level command. (eg. cblsrv WRITE)

Zoltan

Reply to
zcsizmadia

Looks very nice! And the pricing on JTAGkey-Tiny is certainly very attractive.

Aside from lower price and not having a molded plastic case, are there any other differences between JTAGkey and JTAGkey-Tiny?

Thanks, Eric

Reply to
Eric Smith

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