Procedure

Some motorized projection screens, such as Draper, can be made to go up or down via 5-12v logic voltage.  Applying voltage to the control circuit triggers the motor to lower the screen, and removing the voltage (or setting it to 0v) raises the screen.

The Core 110 and the IO8-Flex GPIO Outputs can provide this control voltage with the addition of a small, 1k resistor to act as a "pull up" resistor:



The Core and the IO8-Flex do have internal pull-up resistors but only to a 3.3v rail.  This is the normal TTL-level signal used for controlling external logic devices.  Adding the external resistor, and configuring the GPIO Output as an Open Collector, provides "extra lift" to the GPIO Output to get very close to 12v (actually around 11.5v).