This scanner displays the addresses of all attached I2C devices in a small matrix. The value is shiftet one bit to the left (and is therefore presented as an 8-bit address). The columns show the upper nibble und the rows the lower. As the value is already shiftet, there are only even numbers in the lower nibble.
The device is built with a 0.96" OLED display that plugs into a little PCB with the same size. It is driven with a ATtiny44 with two software I2C ports (one for the display and one scan-port). As the ATtiny44 does not have enough RAM for a screenbuffer and the little boxes are not aligned to the rows of teh display, it uses a simple but nifty algorithm to calculate the screen in realtime.