One way in, three ways out for serial data.
USB I2C click is like a highway intersection for serial data. Bits enter through the USB port and into the MCP2221 USB-to-UART/I2C converter IC. From there, they can take multiple exits. Two of them lead through the mikroBUS™ socket (either I2C or UART). The third runs through an alternative I2C pinout on the edge of the board.
There are even a few GPIO pins on there for good measure. That exit can be closed though, reserved for powering the signal LEDs.
The speed limits on this highway are not restrictive. The MCP2221 chip supports full-speed USB (12 Mb/s) and the I2C works at clock rates of up to 400 kHz, and the UART supports baud rates from 300 to 115200.
Microchip provides a nice configuration utility for testing and using the board, which is nicely demonstrated in our video: