USB data pins behavior while laptop is sleeping/hibernating

[rsfjr87]

Hello all.

I would like to know how the data pins from USB behave while the laptop is sleeping/hibernating/off.

I am building a gadget to detect if the laptop is on state and off state. (referring off as turned off/sleeping/hibernating). In order to turn a USB hub off. (I know it is useless but it is JFF).


Back in the university days I remember that the data pins had pull up resistors. Yesterday I Google it and found nothing.

I don't want to do via Voltage rails because, obviously the USB from a self powered supply will keep them up.

I tried with the SATA 5V rail, but, I'm going to have to remove the HDD or the optical driver.

If I try by the current being drained from the laptop walwart adapter, seems a good idea, but having no power at the outlet does not mean that the laptop is off.


Any ideas?

 

[jsmithepa]

So place a volt meter on data+ and find out.

 

[rsfjr87]

Didn't work.

Data + have a very low voltage while on or asleep .

 

[jsmithepa]

1. You measured data+/GRN right? OK.

2. Individual USB port maybe able to configure to power down, +5v OFF, when asleep.

 

[rsfjr87]

I measured:
1) V+ to GND
2) D+ to GND and V+
3) same thing with D-