You need an USB to GPIO interface hardware, we recommend using one from Numato.
When plugged in it will appear as a new COM port in your Windows system.

Next you have to register the port with Aximmetry.  In the Startup Configuration go to Device Mapper and click Manage Devices at the bottom.

Select GPIO / Serial.

Click Add at Channels.

Choose the COM port which is associated with your USB device and click OK.

The channel is added. Now you have define the input/output configuration of your device. Any of the GPIO slots of the device can behave as input or output, and you have to specify which is which.

In the modes section you can find a predefined configuration by default which specifies the first 4 slots as inputs and the next 4 ones as outputs - and this pattern is repeated throughout all the slots (if there is more).

If you're satisfied with this pattern you're done here.

If not, you have to define another pattern. Suppose you have a 32 slot device, and you want the first 22 as input the rest as output.

Click Add at Modes.

Specify a name for the new mode as you like.

The number buttons represent the individual slots. The checked ones represent the inputs.
In this case check 1 - 22.

(Alternatively you can click All then uncheck the last ten.)

Click OK, the new mode is added.

Click OK. Aximmetry restarts.

Now go to Device Mapper and select GPIO.

Map your COM device, and in the Mode field select the input-output pattern of your needs.

You can start Aximmetry, now you have your device registered.

How to use it?

It can be used like any other controllers, for e.g. you can assign them to buttons.

Suppose you want to use it to control the camera selection or switching between camera motion paths on the standard VirtualCam control boards.

Select the CAMERA board, right-click one of the buttons and choose Assign GPIO.

The learn window pops up.

Now you have to turn on any physical button that is wired into one of the slots of your GPIO interface. The system senses it and the assignment is made.
From now on that physical button switches to Camera 1.

You can do the same for every button you need.

Alternative if you want to control something within the node graph you can use GPIO Input module.
Select your Device and the Channel (which is the number of the slot on the GPIO device).

Alternatively you can use the Learn switch. After turning it on you switch a physical button, and the system automatically selects the Device and Channel for you.

After that State output pin always indicates that the button is down or up. You can use it to control anything you want.

For the opposite direction, when you want to control an external device from Aximmetry via GPIO you have to use the GPIO Out module.

You have to set up the Device and Channel similarly. Of course channel must be an output one.
The State input will be continuously represented as an On of Off state on your GPIO device.