This is a USB device which allows for adding an I2C bus to any computer, designed by Andrew Bradford.
The I2C interface is based on the Microchip USB2221 USB to I2C controller IC along with level shifting to work with I2C bus targets of any typical voltage level (1.8 - 5 V).
I2CU can output DC power to the target (currently there is no current limit built-in so be careful!) programmatically selectable by the host PC from 0 to 5.1 V (up to the incoming USB voltage) in 161 mV steps. If the target provides its own voltage, I2CU is protected from being back-fed.
I2CU can sense the target's voltage, up to 5.1 V and programmatically provide this information to the host PC.
There are 3 green LEDs on the board which indicate the following:
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Input USB power
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Output or target power
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I2C bus traffic
I2CU is designed to utilize as many "house parts" from Macrofab.net as possible and to be able to be built on a 2-layer PCB. Both design goals were set in order to reduce costs for very small volume manufacturing runs (ie: single unit).
I2CU is licensed under the CERN Open Hardware License version 1.2.