[minima] Re: Yet more on Wire.h / I2C FET Interface...
- From: "Steve VK2SJA" <vk2sja@xxxxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Wed, 5 Feb 2014 15:53:57 +1100
Interesting.
This link:-
http://www.varesano.net/blog/fabio/how-disable-internal-arduino-atmega-pullups-sda-and-scl-i2c-bus
Refers to problems with I2C communication if you are using the internal
Arduino pull-up resistors. It would appear that best practice would be to
disable them and use external ones even if you are running in a pure +5v
environment.
Question for Mike and any others working on the bi-directional FET level
converter. Are you using the Ardunio pullups on the +5v side? Does
disabling the internal Arduino +5 pullups and using external ones make any
difference?
Apparently the internal pullups are about 20K.
Here is a link to a discussion on I2C communications with scope waveforms
using different value pull-up resistors.
http://dsscircuits.com/index.php/articles/47-effects-of-varying-i2c-pull-up-resistors
73, Steve
VK2SJA
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