Re: [Gumstix-users] Is 4V enough for 400xm+netCF?

[Alexandre P. N. <al...@om...>]

Adam McLeod escreveu:

>Hi,
>
>  So I'm putting four Gumstix and a PC together on a small switch.
>The PC plus one netCF/STUART card is stable.  The PC plus two
>netCF/STUARTs is stable, as far as I can tell.  At three
>netCF/STUARTs, the network last perhaps 4 minutes before all the eth0
>interfaces on the 400XMs go down, and then come back up, and then
>continue to oscillate.  When all four copies are running, the network
>persists for perhaps a minute.  I'm trying to figure out if this is
>the switch, or the netCFs that causes the problem.  I have 4V power
>supplies for each netCF/STUART combo, and I've tried powering them via
>the STAURT board and the netCF board with no difference in regards to
>the problem.
>
>The switch vendor doubts it is the switch's fault, and my thinking is
>that the 4V supplies might not be able to power the whole three-card
>system.  Any ideas as to what it could be?
>
>Thanks.
>  
>

If I understood your setup correctly, you're using individual power 
supplies to each board, so I don't see where it could make any 
difference for each supply/stix combination to have any number of 
connections through the switch.

As for the power supply expecs, it's not the voltage that matters. 4v is 
the recommended for any ethernet card for the gumstix, because more than 
that make the ethernet chip gets really warm. What's important is the 
current the power supply is able to deliver, in other words, how many 
miniamperes it was designed to sustain on load. If you're using the 
supplies sold with gumstix you should be fine.

The symptoms you describe aren't exactly usual. If the supplies are 
indeed individual, the only common link (and therefore the probable SPF 
[single point of failure]) between then is the switch, but that doesn't 
take away other possibilities.

- Alexandre