On 12/11/22 8:07 PM, Anne Ranch wrote:
My PC is "open architecture " ASUS motherboard in old desktop case. nanoVNA USB port is via powered D_Link " USB hub.
It has not been powered for about 6 months ,,,, I am going to let it fully discharge overnight.
It looks as setting to "continuous sweep" drains the battery pretty fast - perhaps the flashing
"sweep LED" is "too much load "?
The OS still controls (or at least manages) the hub's power as part of the whole USB tree, even if the hub itself receives external power. That is, the hub can decide if it wants to turn power on to a downstream device or not, and the OS (in theory) can find out. The OS can also force a downstream hub to turn off a device.
Considering that (almost) all USB hubs are 4 port devices at the "building block" level, the interlocking state diagrams up and down the chain can be really complex to figure out exactly what is going on.
(Note that this four-ness, is why you see 7 port hubs. It's actually a cascade of two 4 ports, with one hanging off one of the 4 ports of the other).
There's an equally complex negotiation and state machine for data rate through a USB hub.
