Guess PC side is ok, but would choose to put a pullup on the gumstix side =
as well. As long as both the PC and Gumstix is connected the pullup is not =
"used" (pullup resistors are hopefully mounted on the gumstix and the PC =
port will work without)
Til: gumstix-users@... =
Emne: Re: SV: Re: SV: [Gumstix-users] turned my stick into a doorstop
Dato: 28-07-2004 13:59:40
> > It is difficult to tell if the board start correctly because the JTAG =
was newer stable, but most of the times when I boot the board and try to =
read the registers from JTAG I read all 0x00 (or the first one was 0x02 as =
far as I remember). I get the same response when the power is off which I =
interprete as the board did not start correctly (current consumption does =
> > When I can read something else from the registers and no errors occurs =
during the read I tried to run the script, but only successfully once. I =
did get a lot of "internal" errors which according to the readme newer =
> > The type of JTAG I build were the simple one, but with a 3.3V chip =
with 5V tolerent input. I guess the two types are almost identically. If I =
should make a pcb I guess i would choose to put pullups and serie =
resistors on all pins.
> Hmmm. Good point, I guess the 74HC244 I was going to use would not work =
> Which chip did you use for that? The circuit I am going to build from
> http://home.comcast.net/~staskh/projects/tools/ has series resistors on =
> lines but pull ups only on the PC side. So would you recommend them =
> the gumstix side as well?
> > If it's important that the board always start in your application I =
would pay some attention to the power supply circuit, but maybe Gordon has =
changed something on the new stix which may improve the startup.
> > I personally don't think the changed RAM refresh rate will change a =
lot of things regarding startup (but will write if it helps once I manage =
to install a new boot loader).
> - Kim
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From: Kim Hendrikse <kim@ki...> - 2004-07-28 13:45:01
> Guess PC side is ok, but would choose to put a pullup on the gumstix side as well. As long as both the PC and Gumstix is connected the pullup is not "used" (pullup resistors are hopefully mounted on the gumstix and the PC port will work without)
Thanks for the suggestion. I'll put jumpers on the board to enable them or
not. It's not clear to me whether or not a 74HCT244 will work on a 3.7V supply
that I use. Maybe a 74LV244 should be used? In any case, I can always choose to
run the gumstix on 5V whilst I jtag debug I guess. The shops around here don't
have any low voltage chips, I'd have to order them.