You can get the K8055 to send voltage out from the digital ports by doing following:
Connect the minus pole of your external voltage source to the GND terminal of the K8055.
Connect a pull-up resistor between the positive pole of you external voltage source and the digital output of the K8055.
Connect the input of your external device to the digital output of the K8055 and the GND of the external device to the GND of the K8055.
See also: