Zeroplus Arduino starter kit with Logic Analyzer Manual page 100

DESCRIPTION
Getting access to the I/Os of a device is not always a simple
task. An extra board comes in handy to provide external pins for a
measurement instrument.
Suppose you are making a new USB keyboard and you want to make sure
that your implementation of the USB protocol is faultless. The USB
bridge brings the signals out, saving you the cumbersome task of
soldering wires to the I/Os.
In this experiment we would like to capture the keys pressed on the
keyboard, but the computer is constantly polling its USB peripherals
so that we cannot specify any trigger condition because there is
an uninterrupted stream of packets. Instead we rely on a lossless
compression algorithm to extend the duration of the acquisition.