Re: [Gumstix-users] jtag questions

[Zach W. <zw...@su...>]

Gordon Kruberg wrote:
> There is a huge variety of jtag circuits and of usage of tie-high/low
>  resistors.  I believe this version of the gumstix-wiggler 
> interconnection is what I still use day-to-day.

Okay, looking at your schematic confirmed one of my earlier mistakes:
I'd tied in Vbatt where I should have had Vcc...  As a result, the
Wiggler was seeing 5V... and the using that to judge the rest of the
signals.  Needless to say, 3.3V doesn't look "good" in that context.

So... I'd already found myself reattaching that pin to the MIC5255 Vcc
output on the daughtercard.  It would seem to me that this would work
just as effectively for generating the 3.3V reference.  Please let me
know if there are obvious problems using this modified design.

Otherwise, I believe my circuit looks nearly identical to yours at this
point.  The only point of contention is pin 11 on the JTAG header; the
Wiggler pinout guide specifically marks that pin as no connect.  Where
did you find it necessary (or desirable) to connect that pin to ground?

Despite these incremental improvements, I'm still unable to reset the
processor into its test mode.  I'll keep playing with it here, though.

Cheers,

Zach