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Does Gadgeteer need 5V rail


#1

Im trying to hook up a Cerberus to an existing board, and wondered if any of the hardware guys could tell me wether I can take the 3v rail off the donor board and just use that. or does gadgeteer require the 5v rail?
thanks


#2

Gadgeteer requires 5V according to the Gadgeteer socket spec.
But in fact most modules only use 3.3V.
You have to check every single module you use (schematics in most cases).
RS485 for example needs the 5V rail.
Looking at the Cerberus schematics I can see +5V only at the Gadgeteer sockets so I would say the board itself does not need 5V rail


#3

thanks Richard, Ill give it a go


#4

bizzarely it sort of works, on power up it doesn’t run, but pressing the reset button and everything kicks into life


#5

@ Peter Kenyon - You should check the schematics of your board closely, where +5V is connected to (I just had a 20sec. glimpse at the FEZ Cerberus board).
If it’s really just sockets, then there should be no difference for the board if 5V is there or not.


#6

I agree, maybe its the way the rail comes up, I concur that 5v isn’t needed according to schematic, or any of the boards gps, sd card.
I think this works good enough for me… thanks
P


#7

If you have a true Gadgeteer mainboard, the 5v comes from the SP or DP module as either the 5v rail from USB or the output of the 5v regulator. Most mainboards do not use 5v, and it’s only red mainboards (Cobra2 for example) that have a need for it, because they generate 3v3 from it as an SP/DP module does. Most modern processors we’ve been using in netmf all only use 3v3 to power them. Then, it’s about sensors. It’s put on the socket so you can still use a 5v device on the end - there’s still some stuff out there that is in popular use by the *duino crowd that must use 5v, and if you were interfacing to one of those then you’d need to use 5v.

As to why your board needs another reset before operating correctly, I’d suggest it’s power filtering. I don’t think you said what the power donor board was, so perhaps it’s power is a little dirtier than normal; if you can add some filtering capacitors before it hits your Gadgeteer board you might find that this is no longer an issue?