In a blog post from a few years ago, [Peter Molnar] explains in detail how to wire up a physical adapter to add a USB-connected I2C interface to a system. At its core is the ATtiny85 AVR-based MCU ...

It’s a dual USB-to-I2C-or-UART adapter, with a few more oddball features thrown in for good measure. If you were electronics Batman, you’d have this on your utility belt. [Jesus] originally ...