General-purpose input/output (GPIO) is a hardware interface that is not designed for any specific purpose or usage. This means that we can use it as an input or an output. You can think about it as a set of pins that you can use to send electrical signals and you can set them up in software as you wish. (This is why it is called general purpose).
You need a USB to GPIO interface hardware.
When plugged in it will appear as a new COM port in Windows.
Registering the Port
Start Aximmetry Composer...
On the Startup Configuration screen select Manage Devices...
Select GPIO/Serial in the list on the left of the Device Manager
Click Add... at Channels.
Choose the COM port that is associated with your USB device and click OK.
Click OK and the channel is added.
Any of the GPIO pins 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, it specifies the first 4 slots as inputs and the next 4 ones as outputs. This pattern is repeated throughout all the slots (if there are more).
If you're satisfied with this pattern you're done here.
Defining an Arbitrary In-/Output Pin Configuration
Suppose you have a 32-slot GPIO interface, and you want the first 22 as input and the rest as output.
For this, you can add a new Mode.
Click Add at Mode
Specify a Name for the new model as you like.
The numbered buttons represent individual pins. Highlights represent inputs.
If you click on a button, it will be highlighted in blue. If you click again, it will be unselected. You can use the All and None buttons for quick selection.
In our case, we will check 1 - 22.
Click OK when you are done and this new mode will be added to the Modes list.
Modes will be created regardless of Channels, so you can use any combination of Channel - Mode.
Click OK and Aximmetry will restart.
The same rules apply to GPIO device mapping as to all other ones mentioned in the Mapping Devices document.