Sending signals to USB port C

I want to send a simple 开发者_如何转开发5V signal to the usb port. The USB cabel's insulation will be removed and connected to relay connected to an electric door system. I think I should write this code in C. Can somebody give me a hint?

Thanks in advance!

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You can't do this directly but you can buy low cost USB hobbyist/prototyping/interface boards from a number of different vendors, e.g. http://www.devasys.com/usbi2cio.htm.

You might also want to try asking on http://electronics.stackexchange.com since this is more of a hardware interfacing question than a programming question.