[This is a continuation of this post but discussing a new topic]
Spontaneous USB disconnects may happen after shorter or longer uptimes with various 3G/4G modems and the cause may be insufficient DC current served over USB from the router.
I have a Huawei E3276 modem connected to a WNDR3800 router and had these disconnection problems.
I have now tried putting a powered USB hub between the router and the modem but I just got the same disconnection problem again.
The hub I use is a Trust 7-port Pyramid:
Should this hub normally be sufficient to rule out the DC problem when connected to wall power?
I'm having a similar problem with an mt76xx wireless USB card.
I don't the answer but I think any powered hub would do.
Btw, the power block delivered with the Trust hub is marked 5V, 2A, but I don't find any specification about how much is served by each port.
I think it would be a max 2A across all the ports (a max of 500mA/port).
You could assume the Trust Hub supports 4 USB2 ports if they all draw the max at the same time.
I doubt they'd all want 500mA at the same time.
The USB 1. x and 2.0 specifications provide a 5 V supply on a single wire to power connected USB devices. A unit load is defined as 100 mA in USB 2.0 , and 150 mA in USB 3.0. A device may draw a maximum of 5 unit loads (500 mA) from a port in USB 2.0 ; 6 (900 mA) in USB 3.0.
My problem is a bit different, I have both wireless and wired USB3 devices that MIGHT both need 900mA at the same time.
I'm using that same hub to power two HDDs and a SDR receiver, at the same time. It should be good enough to power one modem.
Thanks, great to know that this hub works fine for your setup!
I'll try it out some more. The logs may actually suggest that the disconnects I saw were not power-related but may be related to USB registration timing of hub versus the connected device. I need to have a further look though, at best half-guessing ATM.