JTAG cable/adapter recommendation

Oct 23, 2008 at 5:54 PM
Hi There,

I have bricked my verdex 6LP and need to reflash uboot or eboot. Can anyone recommend a JTAG device that will definitely work with verdex cards. I am about to return an IAR j-link for a refund after trying to make it work for 3 weeks now.

I would send my bricked verdex back to Gumstix for a reflash but the shipping costs to and from Johannesburg, South Africa are more than the cost of a JTAG unit and the round trip would take more than 2 weeks. In any event I suspect that I may need to reflash my boards again in the future (mistakes happen!) so I need to be autonomous.

thanks in advance

Fernando Lo Drago
Oct 24, 2008 at 12:59 PM
Edited Oct 24, 2008 at 1:00 PM
If you purchase the JTAG adaptor offered by Gumstix you are halfway there.
The adaptor has the ability to mate up with the Verdex board's JTAG signals via the pads on the mother board.

I used a "Wiggler" adaptor which uses the parallel port on the PC. There are several clones of the Wiggler on the market. ...some on ebay.
You can also make one for a few bucks.

So it looks like   PC->Parrallel port->Wiggler->JTAG-vx->Verdex morther board.

I have not heard if the new PRO series are compatable with the JTAG-vx adaptor. If they were smart they kept the JTAG pad placement the same on the PRO motherboards.

You can then uses the JFLASH utility (use to be a free give away by Intel). I had to do several mods (they give you the source) and revise the FLASH part personality file to get it all to work.

I did not package these utilities with the BSP as most people would not understand or need them. Its much eaiser just to send it back to Gumstix for a reflash.

If you want I will send you the utility if you really want to dig into it. 

Contact me directly via my Codeplex link.
Oct 24, 2008 at 3:15 PM
Thanks for the info Dave - much appreciated.

In the interests of spreading knowledge to the broader community:  are you using a genuine Wiggler or is it a clone? If it's a clone which one are you using? If it's a diy job would you mind sharing the schematic?

My contribution to the "knowledge base" is: Beware of Segger/IAR j-link adapters, they seem to have a timing problem with respect to the reset protocol for Xscale devices and therefore do not work with Gumstix processors.

I was considering buying the Olimex Wiggler clone (Same unit as the SparkFun -I beleive Olimex make them for SparkFun) but after my experience with the IAR j-link I'm a bit weary of going down that route without confirming correct functioning.

Before I bought the IAR j-link arm I scoured the web looking for a diy solution and I found at leat 8 different permutations of wiggler some passive arrangements with 100 ohm resistors and others with 74XX244 buffer chips. all of them had slightly different mapping of JTAG I/F to Parport and it's not clear which are suitable for Xscale ARM implementations. I have a substantial collection of schematics now if anyone wants to give it a bash.

I do have the Gumstix JTAG adapter. I did consider (for about 3 milliseconds) making one but then realized that I did not know where to get spring test pins so I ordered the real thing!


Oct 24, 2008 at 10:15 PM
The Wiggler clone that I made had two 74XX244's. Don't remember where I got the schemattic from ...somewhere on the Internet.
You don't want to use the the series resistor version. actually one of the original Intel cables used this and its what the original JFLASH utility was written to.
I had problems with the resistor version.
I made some minor mods to the JFLASH source and recompiled ... mostly had to do with the pin mapping and time delays.

The bigest problem is comming up with the FLASH dat file and getting the PXA270's jtag's discription file.. The Gumstix Verdex uses some newer flash parts with odd block sizes at the top and uses it in 16 bit mode.
All this has to taken into account in the dat file.