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servalproject / openwrt

OpenWRT distribution for Serval Mesh Extenders
https://developer.servalproject.org
GNU General Public License v2.0
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USB Port doesn't work on ME2.0 rev2 prototype PCBs #16

Open gardners opened 7 years ago

gardners commented 7 years ago

USB port is non-functional. Sometimes it will see that something is plugged in, but still won't enumerate.

Is the USB header too far from the USB port, thus harming the integrity of the 480MHz signals?

gardners commented 7 years ago

Confirmed that port has power: light comes on, when plugging in a cheap USB serial adapter known to work with linux, but Linux doesn't enumerate the usb device. Doesn't even give a USB bus reset or error that might indicate a marginal USB data link.

gardners commented 7 years ago

WR703N uses a pair of these to condition the positive and negative lines:

http://www.vishay.com/docs/85736/mmbd7000.pdf

gardners commented 7 years ago

It looks like the path lengths of the differential lines is out by more than the 150mil = 3.81mm allowed for HighSpeed USB. Ideally the difference should be much less than this.

gardners commented 7 years ago

Tried cutting the traces close to the module, and then soldering half a USB cable directly on, but no help.

gardners commented 7 years ago

Also tried ensuring GPIO13 is pulled up high properly, to force USB into host mode instead of device mode. Still no luck (with our soldered-on half USB cable -- maybe now it would have worked with the original port?)