[minima] Re: Wire.h library modifications
- From: Michael Yancey <mikeyancey@xxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Thu, 30 Jan 2014 08:52:49 -0600
Yes - exactly!
The 3.3V devices on the Source-side of the FETs, pullup with 'R' to 3.3V;
The 5.0V devices on the Drain-side, pullup with 'R' to 5V;
FET gates tied to 3.3V
Whole thing is bi-directional.
That way, I can be assured, without changing the Arduino Wire.h source,
or, more probably - re-installing / updating / moving to another machine
where the 'comment-out' in twi.c hasn't been done - none of these will
harm the Si570. So you can feel comfortable, a year later, re-programming
or updating the code without thinking: "Hmm... now did I comment out
those pullups in twi.c?" (or, if you're using a Mega - no dismembering
pullup
resistors from the board...
It's two FETs, 4 resistors - I don't even think you need 10k resistors,
values
not critical. FETs aren't critical BS170 (identical to 2N7000).
Mike Y
------------
From: Dan Reynolds <on30ng@xxxxxxxxx>
Date: Wed, 29 Jan 2014 16:54:21 -0600
Subject: [minima] Re: Wire.h library modifications
Michael, is it like this circuit:
http://www.nxp.com/documents/application_note/AN10441.pdf
I saw one application and they used 10K resistors. Seems like this would be
handy too when changing the code on the Arduino chip while it is in
circuit. A good "just in case" handy thing to have in place (like a diode
in the power supply line...).
--
..
Mike Yancey
Dallas, Texas
http://www.mikeyancey.com
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