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Parallel printer port, which was often used for this kind of hacks, disappeared from PC several years ago. A USB device is usually the best for general purpose
by kazuya 16y ago
Parallel printer port, which was often used for this kind of hacks, disappeared from PC several years ago. A USB device is usually the best for general purpose I/O.
And I don't know how to build a USB device 'with a couple of logic gates'.
- lutorm 16y agoIs it not possible to simply steer the USB pins high or low just like with a serial port?
- kazuya 16y agoInteresting idea, but I believe it's very hard to trick the USB host controller into flipping pins as you intend.
- Murkin 16y agoNope, The controllers on both ends expect a fairly complex protocol (one which you have virtually zero control over - in software). Some hubs will allow you to selectively turn power on their ports (most just say they do). You can in theory stick leds there.
- lmz 16y agoUSB is a complex protocol, encoded using just two wires (the other two are power - +5V and GND). There are no pins you can steer high or low. See http://www.beyondlogic.org/usbnutshell/usb1.shtml http://www.beyondlogic.org/usbnutshell/usb1.shtml for more info.
- jws 16y agoUSB also provides enough power to light a bright LED. There was no power on a printer port, though people would steal power by setting a lot of pins high and hoping for the best. I think I'd just spend the $2.40 and use an AT90USB82 instead. It has USB built in so you don't have to wrestle with software USB. I've done software USB on an Atmel and getting 98% of the way there is easy, but I never really trusted the end result. On the down side, it doesn't come in a DIP package, but you could use any little breakout carrier card to get to the pins. On the plus side you'd have a couple dozen pins to play with.