With the GiOConfig application installed you can determine whether the buttons on the GiO are transmitting data. Double-click and open GiOconfig from the Mac's Applications folder. Under the Expression pedal curve setting you'll see a Value: and grey rectangular bar. When pressing a button on the GiO the rectangular bar should turn blue and a Value of 127 displayed. This would indicate that GiO is transmitting MIDI data to the Mac and can be checked with all the buttons of the GiO.