Re: [Gumstix-users] connecting gumstix and robostix serial with different supply voltage

[Dave H. <dhy...@gm...>]

Hi Esger,

> Now if I have the robostix and gumstix connected through the hirose conne=
ctor,
> the robostix is powered through that with apparently around 3.3 volt.

Actually, the robostix provides the power to the gumstix. The robostix
runs at 5v. There are actually 4 voltage regulators on the robostix
board.

> However in my understanding that also limits the gpio and adc inputs of t=
he> robostix to that 3.3 volt. If I power the robostix separately with 5 vo=
lt I
> see that 5 volt also on its vcc/gnd and io's.
>
> It probably isnt a good idea to power both while connected through the
> hirose...

Are you using a daughtercard? I've heard of a couple of cases where
the robostix combined with something like a netCF was drawing too much
power and they had to power both.

I use a robostix/gumstix-400xm/netMMC and I power the whole stack by
using the power jack on the robostix.

If I used the power jack on the netMMC card then the voltage
regulators on the robostix wouldn't work properly.

> So if I want to be able to use higher voltages on the io of the robostix =
I
> need to separate the modules. I still need to communicate to get the valu=
es
> from the inputs though. Currently I'm using a serial connection since i2c
> seems to slow (I need an update rate of 60Hz or better), at least it is w=
hen
> using the supplied test programs.
>
> The question is, if I power the gumstix and robostix separately, can I co=
nnect
> the uarts with no further trouble? Seeing that one vcc will be 3.3 and on=
e 5?
>
> Or do I need to add something to make sure it works, or even to prevent w=
orse.

I'm not sure what you mean by powering the gumstix since it doesn't
haave any power jacks.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/