userial is an Free project building an USB to I2C/SPI/GPIO bridge, using the Atmel AT90USB647 chip. Hardware and Software are released under an Open Source licence. It supports the following interfaces: * USB interface (serial emulation) * JTAG * I2C (TWI) * SPI * 8 General purpose digital I/O * 4 Analog to Digital converters (currently no firmware support)