Please keep in mind that I am very new to reading circuit diagrams, and electronics in general. I am interested in using V-USB to connect my AVR microcontroller to my computer via USB. On the V-USB website, the following sample diagram is given, and I have some questions.
- USB Pin1 to ATTiny VCC: Why is there a ground connection as well, and what purpose does C4 serve? Traditionally, I am used to connecting a wire running 5V to VCC, but not hooking that up to ground too. I thought the ground connection is made internally, because I am connecting the ground from the power supply (in this case, USB cable) to the GND pin of the microcontroller already.
- You see how C2 and C3 are connected via one line to GND? Would this be equivalent to connecting them individually as well? So the negative end of each capacitor would be running on its own to ground instead of meeting up, and then going to ground. Or is it depicted like this to save space in the diagram?
- What is the purpose of C1? Isn't it creating a short circuit? I don't understand why it is there if the loop from USB Pin4 to USB Pin1 (which has C1 in it) does not access any of the pins on the microcontroller. Does C1 still impact the overall circuit somehow?
- Why does D- have R3 and a voltage connection, whereas D+ does not?
- Is R3 meant to pull up D- to a high logic level when PD3 (on the ATTiny) is not providing any input? Why?
I know these are a lot of questions, but I need to overcome my fear of circuit diagrams. I think there is a fundamental flaw in my process of understanding them. I think of the lines as physical wires and think of current as little dots following the paths in diagram - childish, I know.
Thanks for your help, any advice in general about reading circuit diagrams would be awesome too.