More info about: why are the leds off from my GPSDO, when USB connected and, my PC is off power.
Did read the datasheet of the PIC to see how the USB works, and analyse what can be wrong or not.
for the other readers, see picture of the USB interface, and some explanation.
The D+ line (see picture) is set high to inform the host that it can work on high speed USB
When D- is set high, same that it can work on low speed USB
When both D+ and D- are low, that is called a: single ended zero situation, means connection ended or disabled, or reset.
When both D+ and D- are high, there is an error condition should not be possible.
What happens when the GPDSO is connected to my PC, when it is off with no power, the PC pulls down the D+ and D- lines of the USB.
That should be correct, it goes to the single ended zero state.
Checked some other devices, but not alle devices pull the lines down when off power.
So not all devices are implemented the same, on this point.
In the datasheet of the PIC of the GPSDO (see first post for the PDF), on power up it checks for single ended zero state. ( SE0 )
In my case, PC off power, the GPDSO detects the SE0 on startup and sets the register flag for that, what is correct. (chapter 24.2)
This situation is monitored until it come out of the SE0 state, during start up.
So what happens i think, as the two leds of the GPSDO are used to signal error conditions,
the off state of the leds, is also a condition to let it know there has been an USB error, because the unit stay working oke, without USB.
So to me it looks all correct, it has only to be applied to the manual of the GPSDO.
But Leo is still looking into it.