On 11/12/2013 7:09 AM, luke.leighton wrote:
On Mon, Nov 11, 2013 at 2:10 AM, Christopher Havel laserhawk64@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_fo...
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