[Arm-netbook] apologies

[Christopher Havel]

On 11/12/2013 7:09 AM, luke.leighton wrote:
> On Mon, Nov 11, 2013 at 2:10 AM, Christopher Havel
> <laserhawk64 at gmail.com> wrote:
>> On 11/10/2013 9:08 PM, luke.leighton wrote:
>>> apologies to everyone on the list - you may have noticed i'm using
>>> brief and curt language at the moment.  it's not personal: i just have
>>> far less time available and have to be very focussed.
>>> l.
>>>
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>> Sorry to hear you're so busy. Can I help? :D
>   yes.  i thought of something.
> http://permalink.gmane.org/gmane.comp.hardware.netbook.arm/7597
>
>   could you investigate, find some "educational" style electronics
> explanations online, as to why henrik's recommendation to use a
> pull-up resistor to 3.3V and a reversed-diode between the Tx UART and
> incoming Rx actually works?  i'm attaching a small diagram showing the
> circuit.
>
>   it can then be added here:
> http://elinux.org/Embedded_Open_Modular_Architecture/EOMA-68#Requirements_for_UART
>
>   also i think.... to avoid too big a voltage-drop it should be a zener
> diode otherwise it might interfere with the thresholds.
>
>    basically i think the way it works is that 0 logic level on UART is
> "positive voltage", and the Tx line "sucks" current down to GND in
> order to indicate a "1".  therefore, normally (i.e. without the diode)
> current would be flowing *from* Rx *to* Tx if Tx is held at GND to
> indicate a "1"... so putting the diode in the circuit is... well...
> normal!
>
> l.
>
>
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Try this :) it popped up on Google pretty quickly --> 
http://www.hobbytronics.co.uk/schottky-logic-level-conversion
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