Disclosed embodiments provide a configurable electronic credential reader. The electronic credential reader defaults to a first communication mode utilizing a unidirectional communication interface. A bidirectional communication interface is monitored. If data is detected on the bidirectional communication interface, the electronic credential reader switches to a bidirectional communication mode. Circuitry within the electronic credential reader switches between the unidirectional communication interface and bidirectional communication interface such that the same external communication lines are used for both the unidirectional mode and the bidirectional mode.