I'm designing a PCB for an astronomical observatory which needs several Arduino Micro to control different devices. Since the circuit must fit a very small space, I'm putting an onboard USB hub to connect all the three ATMega32U4 (instead of putting 3 full Arduinos, hub and USB cables). There will be one micro USB connected to the PC. Something like this:
However, I'm confused about:
- How to connect the various D+ and D- pins of the AVRs with the DP and DM pins of the Genesys GL850G USB 2.0 Hub Controller I'm using. Which shall be connected where? (I fear exchanging them)
- Whether or not I really need all the capacitors, ferrite filters and inductors shown in this example of GL850G usage: what are they used for? Why so many capacitors in parellel on the 3v3 line instead of one bigger capacitor? And why is +3.3V needed?
- Is this a valid circuit for a simple ATMega34U4? Same here, why so many capacitors in parallel (between VCC, AVCC and GND)?
- The hub and the whole circuit shall be powered by a bigger 5V power supply instead of the USB standard 500mA. Is it a good practise if I just leave unconnected the PC USB power and give the circuit another +5V?