Re: [Gumstix-users] Logic level converter from 1,8V to...

[Scott E. <sco...@gm...>]

I'm just a software guy, so beware, but I did it this way for I2C
using that Sparkfun part. Works.

http://github.com/scottellis/overo-blinkm/blob/master/blinkm_simple_circuit.png

On 1/7/10, Ors Tiszay <lis...@gm...> wrote:
> Hi,
>
>
>
> On Sat, Dec 5, 2009 at 5:12 AM, Dave Hylands <dhy...@gm...> wrote:
>
>> Hi Ors,
>>
>> On Fri, Dec 4, 2009 at 3:25 PM, Kukac Lista <lis...@gm...> wrote:
>> > Hi,
>> >
>> > And which one would you use for the 1-wire pin?
>>
>> Oh yeah - I forgot about that one. 1-wire uses an open-drain
>> configuration and requires an external pullup (I believe to 1.8v).
>> Since it's also bidirectional (like i2c - which is also an open-drain
>> style interface) any of the i2c level converters should work.
>>
>> Sparkfun also sells a level converter:
>> <http://www.sparkfun.com/commerce/product_info.php?products_id=8745>
>>
>> It has two active level converters and two passive level converters
>> (resistor divider). The resistor divider can be used for some
>> unidirectional signals, but typically only at slow speeds.
>>
>> The active ones can be used for i2c and  1-wire. They can also be used
>> for non-open drain voltage conversion if you only have a few pins. For
>> more pins going to one of the bigger chips that can convert 8 pins at
>> a time may be better
>
>
> I'm only trying to use it for one pin, the 1-wire line of the Chestnut43,
> but I'm not sure I understand how to use the level converter from Sparcfun
> for this purpose. Where do I connect the 1-wire pin? RX or TX? The
> connections seem to be one way only, either TX or RX. Looking into the
> schematic, the active converter seems to handle TX, RX being connected to
> the passive divider, but the one-wire is two-way. It's been a long time
> since I looked at a schematic of anything, but it seems that the active one
> would not work "backwards" with the drain being controlled only by TX_LV.
>
> Just for the archive's sake: Maxim has a reference design for this very
> purpose here: http://www.maxim-ic.com/app-notes/index.mvp/id/4477/. Problem
> is, being located in Hungary, I can't seem to find a reseller with MAX3394E
> is stock.
>
> br,
> Ors
>