When dimming backlight on the Hatteland Technology's Series X units to zero the GDC (Glass Display Control) buttons may become difficult to see in daylight.
In general, the brightness of these buttons follow the brightness of the panel, however we are now setting the minimum brightness of these buttons to GMB 0x04 from factory. It might still be hard to see in daylight but a higher value may be disruptive at night.
Nevertheless, customers can also set their own brightness value, please review this "Service Memo" document for procedure and more information: Service Memo: 9 Sep 2016