Self-powered USB "pass-through"?
Posted: Mon Jan 07, 2008 7:17 am
Hi All!
I have a laptop on which I damaged the USB port, about 1 1/2 years ago when I was learning about the PIC 18F4550 and USB devices. In short, the USB ports no longer supply power, but they work with self-powered USB devices.
The laptop is now my wife's, and I wanted to make a device for her that would supply power to small, port-powered USB devices (like data sticks), so she can use the port with other devices.
I created a simple PCB that provides power to a device using a step-up converter for 2 AAA batteries (MAX1676), and simply passes D+/D- to the USB port.
The circuit does provide power to the device, however, nothing happens when I plug in a data stick (tested it on a good computer, and the device works fine on its own).
Since then, I've read that you need to "sense" a cable connection when a self-powered USB device is plugged in.
Does anyone know the details on this? Do I have to use a microcontroller for this type of app? And, is this type of device even possible?
Thanks in advance for any assistance!!
I have a laptop on which I damaged the USB port, about 1 1/2 years ago when I was learning about the PIC 18F4550 and USB devices. In short, the USB ports no longer supply power, but they work with self-powered USB devices.
The laptop is now my wife's, and I wanted to make a device for her that would supply power to small, port-powered USB devices (like data sticks), so she can use the port with other devices.
I created a simple PCB that provides power to a device using a step-up converter for 2 AAA batteries (MAX1676), and simply passes D+/D- to the USB port.
The circuit does provide power to the device, however, nothing happens when I plug in a data stick (tested it on a good computer, and the device works fine on its own).
Since then, I've read that you need to "sense" a cable connection when a self-powered USB device is plugged in.
Does anyone know the details on this? Do I have to use a microcontroller for this type of app? And, is this type of device even possible?
Thanks in advance for any assistance!!