Is there anyway to send commands to the Cerb40 via its USB client port?
that would be CDC. Cerb has USB Client listed as Debugging Only. So no.
@ Brett - No, not necessarily via CDC, just any communication to the running program.
CDC is the most common “simple” way to interface. The alternative is to have a USB Client app. But Cerb does not implement anything other than USB debugging over USB client as per specs, so the answer is still no.