Hi - does anybody know of a simple USB chip that would allow me to turn on/off a simple circuit? A single low current pin that could be brought high or low would be enough for me... Is there anything out there that is fairly simple to implement?
http://www.futurlec.com/USB.shtml There are several differint models on there, the one that might interest you the most is the "USBMODIO24": USB I/O module for connecting up to 24 digital inputs or outputs to the module. Each unit has a unique ID, to allow expansion of up to 128 modules to connect to the one PC. Module can be easily read or written to by using Visual Basic or other high level languages. Ideal as a starting point for a home control or industrial control system. It costs loads more than the other models though, but those aren't "simple input/outputs", you'll need to add a microprocessor (like a PIC) to interpret commands send through the serial interface.
The version 2 FTDI USB chips have a feature called 'Bit-Bang' mode. In this mode the 8 data lines can be programmed as inputs or outputs and when in output mode the bit(s) can be set to a 1 or a 0 and then remain in that state until a subsequent command changes that state. This means that what you want to do is very simple and no additional processor chip is required. The FTDI chips are surface mounted so unless you are happy with building circuits that use surface mount technology it is easier to use one of the many modules that are available that host the version 2 FTDI chips. A good idea of what is possible can be seen here: http://www.dlpdesign.com/images/bit-bang-usb.pdf. Good luck.
I have a 1-Wire demo kit (which I purchased from a friend), which included the USB adapter and 8 different chips (2 EEPROMs, 2 RTCs, 2 digitally adjustable resistors, and 2 electronic switches). I say that 1-Wire is the way to go! Another option is a PIC with USB or a PIC with RS-232 and a RS-232 to USB converter.
