Hi to all!
I'm designing board using Raspberry CM.
I need USB devices such pendrive, USB to serial (I need several serial ports), wireless card....
I found USB hub chip and all devices are USB 2.0; all devices has gor own USB power switch.
I don't need to plug/unplug them, they are all fixed to main board.
I've found a lot of documentation about USB bus design, but in fact it's all for "plug'n'play" items.
As I said, I don't need to plug/unplug devices and I read I just need to follow these rules:
- differential impedance 90 Ohm
- keep at least 1mm away from any kind of ground plane or traces
- keep same trace length as I can
- 27 ohm series reisitor on trace
Ok, any suggested considerations about USB layout for CM?