Hello,
I'm connecting my Arduino Duemilanove to a 3.3V interface. In order to not risking damage to my interface, I want to disable the pull-up resistor for both Tx and Rx.
Using this code:
DDD0=0;
PORTD0=0;
DDD1=1;
PORTD1=0;
The problem is that the Arduino Compiler don't accept these commands. I'm doing this wrong? Anyone has another method? Or I simply can't change these setting in Arduino envirioment?
To use those definitions I believe you need to include
the io constants. Place the line below at the top
of your sketch.
#include <avr/io.h>
An open-drain line without a pull-up is going to have a very slow
rise-time and may cause you other problems. The best way to interface
between the two logic levels is to use a buffer with 5V tolerant inputs.
The buffer is power off of the 3V3 supply. I use the 74AHC14 for
this purpose.
(* jcl *)