From: Nate W <delaminator@gm...> - 2005-11-11 08:43:45
I mentioned this a while ago, but: I have a servo controller connected
to the console serial port (aka FFUART, aka the "Gumstix" port on the
robostix) and when I power up, the gumstix boot messages confuse my
I was going to try to solve the problem by toggling the servo
controller power, then looked into toggling the servo controller's
reset line (it's a PIC and MCLR is easily accessible) but I think I
found a very simple solution: turn off the console's serial level
shifter as soon as u-boot starts running, then enable the shifter at
the very end of the Linux boot process, when the boot messages are
over and my code is ready to talk to the servo controller.
But first I'd appreciate a sanity check... are the following all true?
Setting GPCR2 to 0x0 and GPSR2 to 0x340 will set GPIO70, 72 & 73.
This will turn off the level shifter, turn on the Robostix, and put
the Robostix in reset.
With the shifter off, there will be no activity on the Robostix'
"Gumstix" serial port while u-boot and Linux boot up.
(I won't be able to log in over the serial port this way, but that's
OK because I usually log in via bluetooth anyhow.)
I *will* be able to access the console if I plug the Gumstix into a
waysmall board, so I can still talk to u-boot if I need to. That's
the thing I'm most concerned about - will these GPIOs affect the
waysmall serial ports at all? I don't see anything to that effect in
the Wiki documentation but I'd like to be sure, lest this be the last
time I ever see a u-boot prompt from this board. :-)
Redmond WA USA
http://www.natew.com/ <=3D=3D for nerds
http://www.featherforum.com/ <=3D=3D for birds
From: Dave Hylands <dhylands@gm...> - 2005-11-11 17:06:45
> But first I'd appreciate a sanity check... are the following all true?
> Setting GPCR2 to 0x0 and GPSR2 to 0x340 will set GPIO70, 72 & 73.
Setting GPCRx or GPSRx to 0 is a no-op. They only respond to ones.
> This will turn off the level shifter, turn on the Robostix, and put
> the Robostix in reset.
Well, it will remove the power from the level shifter. However,
whenever any of the the lines going to the 245 are high, they will be
able to power the device using leak thru current.
Rather than turn off the '245 why not just reconfigure GPIO 34 & 39 (I
think these correspond to FFUART) as GPIO's. That will cause no data
to be sent.
> I *will* be able to access the console if I plug the Gumstix into a
> waysmall board, so I can still talk to u-boot if I need to.
Using the reprogram the GPIO pin method, you'd be able to get into the
GUM prompt and use a different boot command which didn't reprogram the
> the thing I'm most concerned about - will these GPIOs affect the
> waysmall serial ports at all?
Those GPIOs are all LCD data lines.
> I don't see anything to that effect in
> the Wiki documentation but I'd like to be sure, lest this be the last
> time I ever see a u-boot prompt from this board. :-)
You're talking about writing the registers using the u-boot scripting
stuff right? In which case you can always repower and get into the GUM
Vancouver, BC, Canada