# Just Launched: You can now import projects and releases from Google Code onto SourceForge

We are excited to release new functionality to enable a 1-click import from Google Code onto the Allura platform on SourceForge. You can import tickets, wikis, source, releases, and more with a few simple steps.

## gumstix-users

 [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Martin Maurer - 2005-05-27 06:09:13 Attachments: Message as HTML ```Hello, i want to connect my own hardware to a I/O-Pin.=20 1) Is it correct, that gumstix (on all GPIO ?) outputs 3,3V level and = accepts only 3,3V levels ? So when i have 5V level for an input of the = gumstix, how i can connect them ? Is a resistor enough or do i need a = level translator ? 2) Is there any possibility to get 3,3V out of the gumstix from the on = board regulator ? How much mA can i draw ? Or can i only get the power = from the main power supply and use my own regulator ? Regards, Martin ```
 Re: [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Dave Hylands - 2005-05-27 13:58:57 ```> i want to connect my own hardware to a I/O-Pin.=20 > =20 > 1) Is it correct, that gumstix (on all GPIO ?) outputs 3,3V level and > accepts only 3,3V levels ? So when i have 5V level for an input of the > gumstix, how i can connect them ? Is a resistor enough or do i need a lev= el > translator ?=20 On the Robostix, one 74LVC4245A is being used to convert from 3.3v to 5v and another is being used to convert in the other direction. This particular chip can convert 8 lines. There are devices available with single and double lines. You could use a resistor divider to convert from 5v to 3.3v, but not to go in the other direction. It really depends on what kind of device you're connecting up. If you connected a 6.8k resistor and a 3.3k resistor together across 5v, with the 6.8k connecting to ground and the 3.3k and the 3.3k between +5 and the 6.8k, then you'd get 3.36v where the 3.3k and 6.8k join. Some 5v devices will treat a 3.3v signal as a high, so you may be able to connect them directly if the gumstix GPIO is being used as an output. > 2) Is there any possibility to get 3,3V out of the gumstix from the on bo= ard > regulator ? How much mA can i draw ? Or can i only get the power from the > main power supply and use my own regulator ?=20 No. There is no 3.3v available on the connector. All of the expansion boards have their own voltage regulator on them. The MIC5255 is the one used on most of the expansion boards: http://www.micrel.com/product-info/products/mic5255.shtml --=20 Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ ```
 Re: [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Brad Midgley - 2005-05-31 21:32:22 ```Dave > You could use a resistor divider to convert from 5v to 3.3v I am just a menace to anything other than software (maybe software too), but could you give me an idea of how to choose the resistors for this? I see one from the 3.3v lead to 5v and one pulling the 3.3v lead down to ground (I think). Do people actually build these out of two resistors or just buy an IC? Brad ```
 Re: [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Dave Hylands - 2005-05-31 22:24:33 ```Hi Brad, > > You could use a resistor divider to convert from 5v to 3.3v >=20 > I am just a menace to anything other than software (maybe software too), > but could you give me an idea of how to choose the resistors for this? I > see one from the 3.3v lead to 5v and one pulling the 3.3v lead down to > ground (I think). Do people actually build these out of two resistors or > just buy an IC? It depends on whether you care about current consumption or not. Using two resistors will work (in the 5v to 3.3v direction), but using an IC will draw less current. If you're using a battery it might make a difference (it would also depend on how many lines you're doing this with). I mentioned in my previous email that picking a 6.8k and 3.3k resistors would work fine. This gives 10.1k at 5v which would draw half a milliamp when the 5v signal is at 5v and won't draw any current when the 5v signal is at 0v. You woulkd connect them something like this: +--5v signal | | 3.3k resistor | | +--- goes to gumstix GPIO pin | | 6.8k resistor | | +-- goes to 5v ground and gumstix ground You could also use a RoboStix when it's available since it will have 5v I/O> then you'd just need to write some software to send stuff back and forth. --=20 Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ ```
 Re: [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Brad Midgley - 2005-06-01 18:04:52 ```Dave, I should have been paying better attention to the original thread... I actually need this circuit turned around if possible :) I don't care about power consumption since I am just prototyping... but what I want is the simplest circuit to power a 3.3v external device (bluetooth class 1 module) using the gumstix 5v supply, perhaps switched on & off from a gpio if that doesn't complicate it. Brad Dave Hylands wrote: > Hi Brad, > > >>>You could use a resistor divider to convert from 5v to 3.3v >> >>I am just a menace to anything other than software (maybe software too), >>but could you give me an idea of how to choose the resistors for this? I >>see one from the 3.3v lead to 5v and one pulling the 3.3v lead down to >>ground (I think). Do people actually build these out of two resistors or >>just buy an IC? > > > It depends on whether you care about current consumption or not. > > Using two resistors will work (in the 5v to 3.3v direction), but using > an IC will draw less current. If you're using a battery it might make > a difference (it would also depend on how many lines you're doing this > with). > > I mentioned in my previous email that picking a 6.8k and 3.3k > resistors would work fine. This gives 10.1k at 5v which would draw > half a milliamp when the 5v signal is at 5v and won't draw any current > when the 5v signal is at 0v. > > You woulkd connect them something like this: > > +--5v signal > | > | > 3.3k resistor > | > | > +--- goes to gumstix GPIO pin > | > | > 6.8k resistor > | > | > +-- goes to 5v ground and gumstix ground > > You could also use a RoboStix when it's available since it will have > 5v I/O> then you'd just need to write some software to send stuff back > and forth. > ```
 Re: [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Dave Hylands - 2005-06-01 18:22:11 ```Hi Brian, > I should have been paying better attention to the original thread... I > actually need this circuit turned around if possible :) >=20 > I don't care about power consumption since I am just prototyping... but > what I want is the simplest circuit to power a 3.3v external device > (bluetooth class 1 module) using the gumstix 5v supply, perhaps switched > on & off from a gpio if that doesn't complicate it. Ahh - That's a completely different problem. If you're just trying to get power, you should be able to "steal" it from almost any of the expansion boards. What expansion board (if any) are you using with the gumstix? If you want to control it (on/off) then you need to be a lot more careful and you'll probably need some type of interface circuitry in all o the GPIO lines. Otherwise, you can inadvertently power the device using current leaking through the GPIO lines. --=20 Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ ```
 Re: [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Dave Hylands - 2005-06-01 18:21:36 ```Ooops - I meant Brad. Previous email I sent was to a Brian... On 6/1/05, Dave Hylands wrote: > Hi Brian, >=20 > > I should have been paying better attention to the original thread... I > > actually need this circuit turned around if possible :) ... snip ... --=20 Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ ```
 Re: [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Brad Midgley - 2005-06-01 19:10:19 ```Dave, I just have audiostix and a tweener. I was planning to break into the uart lines using the tweener. I realized after I wrote the last message that gpio control would be ugly. Brad Dave Hylands wrote: > Hi Brian, > > >>I should have been paying better attention to the original thread... I >>actually need this circuit turned around if possible :) >> >>I don't care about power consumption since I am just prototyping... but >>what I want is the simplest circuit to power a 3.3v external device >>(bluetooth class 1 module) using the gumstix 5v supply, perhaps switched >>on & off from a gpio if that doesn't complicate it. > > > Ahh - That's a completely different problem. If you're just trying to > get power, you should be able to "steal" it from almost any of the > expansion boards. What expansion board (if any) are you using with the > gumstix? > > If you want to control it (on/off) then you need to be a lot more > careful and you'll probably need some type of interface circuitry in > all o the GPIO lines. Otherwise, you can inadvertently power the > device using current leaking through the GPIO lines. > ```
 Re: [Gumstix-users] I/O-Pin-Level (in / out) and getting power (3,3V) out of gumstix ? From: Dave Hylands - 2005-06-01 19:56:58 ```Hi Brad, > I just have audiostix and a tweener. I was planning to break into the > uart lines using the tweener. Both of these boards have 3.3v regulators on them. I don't have mine with me right now, but it should be possible to locate a via that a wire could be soldered into in order to get at the 3.3v. The tweener board actually has a via for every (or almost every) signal on the 60 pin bus, since they pass through from top to bottom, so getting at other GPIO lines should work fine too. You'd need some 30 gauge wire wrap wire, which is small enough to fit in the vias. So you could tap into the HWUART or STUART lines without losing your consol= e. --=20 Dave Hylands Vancouver, BC, Canada http://www.DaveHylands.com/ ```