PORTS Forum

Ports and Interfaces => USB => Topic started by: fernandoRojas on September 08, 2017, 08:49:30 am

Title: SimpleHIDWrite activates port, but how?
Post by: fernandoRojas on September 08, 2017, 08:49:30 am

Dear all,

I've been working with a USB interface on Windows 7 without problems. Some months ago I started to work on Windows 10 pro.
This Windows version is known to have some issues with USB Powering. I did some research and found the following posible power states:

D0 - The working state. The device is fully powered.
D1/D2 - The intermediate sleep states. These states allow the device to be armed for remote wakeup.
D3 - The deepest sleep state. Devices in state D3 cannot be armed for remote wakeup.

My device is set to sleep (goes to D3) after my application is closed. On Windows 7 it would always stay on D0.
However, opening SimpleHIDWrite activates the port miraculously (goes to D0). Does anyone have an idea of what is happening?

I suppose there is a part of the code in SimpleHIDWrite which initializes USB Ports, but how?
How could I replicate this behavior?

Thanks in advance

Title: Re: SimpleHIDWrite activates port, but how?
Post by: Jan Axelson on September 08, 2017, 04:03:43 pm

I didn't write SimpleHIDWrite and don't have the source code.

Perhaps it attempts to open a handle to any detected HIDs?