I hope I'm in the right spot. I swear I'm the opposite of Rainman when it comes to electronics. I think I got too late of a start.
Ok, so my first question is about the ATMEGA1284:
In the datasheet, it has the following:
"As inputs, Port C pins that are externally pulled low will source current if the pull-up
resistors are activated."
If the pull-up resistors are activated, aren't I telling the uC that I want it to "receive" the signal? Why would it put out a source?
And I guess secondly, why would I want to use the internal pull-ups? I tried searching for this answer, but apparently, my google searches suck, cuz I never find what I'm looking for.
This all brings me to my second question involving pull-ups:
I read in this older forum:
http://forum.arduino.cc/index.php?topic=46963.0
that using i2c, for 3.3V components, I can just use a 4.7k resistor to pull-up to 3.3V and I should be good? For some reason, I think I either read that wrong, or I'm an idiot. That can't be right, can it? I'm trying to hook up an ov5642, but it runs on 3V(everything I've read says I should still be able to get away with the 3.3V. So, if I wanted to hook that up to an Uno or a Mega, without a shift register, I would have to get the SDA and SCL down to 3.3V, Right? But I also read that the return signal from the camera module might not read it properly because of those internal resistors. I know I can comment out those lines, in twi.h, but now with this last thing I read(forum link above), I'm extremely confused.
And with all that, if I were to use a voltage divider and got the signal down to 3.3V, does that have to be on both SDA and SCL? If so, when it sends information back, wouldn't that be divided even smaller? If the Uno or Mega(if memory serves me correctly) needs atleast 3V(3.3V?) on a digital pin to be considered HIGH, then how would that work?
My head is spinning right now. I feel like I'm just running around in circles with all of this, and none of it makes sense. Please help. I feel so stupid, even though I do understand so much of this stuff, I just can't seem to wrap my brain around a lot of it.