Firstly, my electronics experience is somewhat rusty so please bear with me; I last picked up a soldering iron in anger some 15+ years ago when I did electronics at school.
I'm having a stab at recreating the Delorean Time Circuit project with my Pi. As a result I need to wire together a few LED Backpacks to achieve the effect. I have a couple of (probably very newbie) questions as a result
1) In the excellent article about the backpacks and a Pi it suggests using a logic level converter (http://learn.adafruit.com/matrix-7-segm ... rything-up) if running at 5v. Do I need to just wire the Pi SDA/SCL to A1, B1 and the multiple backpacks into A2, B2? Or do I need to use one channel pair per backpack?
2) If I'm powering the backpacks via the 3.3v rail does this do away with the need for a logic level converter
3) If I power the backpacks via an external 3v power supply (2xAA) will this cause any problems? I have a feeling that I'm going to run out of juice if I power the whole lot via the Pi.
For reference I have 3x 7-Segments on a backpack, they're common anode and with some funky looking bit bashing code I have successfully driven them for my needs at 3.3v. Now I want to add a further 2 more backpacks.