Modified from here
| Pin Type | Description |
|---|---|
| Input | A pin which is exclusively an input. |
| Output | A pin which is exclusively an output. |
| Bidirectional | A pin that can be either an input or an output, such as a microcontroller data bus pin. |
| Tri-state | A three state output pin (high, low, or high impedance) |
| Passive | A passive symbol pin: resistors, connectors, etc. |
| Free | A pin that can be freely connected to any other pin without electrical concerns. |
| Unspecified | A pin for which the ERC check does not matter. |
| Power input | A symbol’s power pin. As a special case, power input pins that are marked invisible are automatically connected to the net with the same name. See the Power Ports section for more information. |
| Power output | A pin that provides power to other pins, such as a regulator output. |
| Open collector | An open collector logic output. |
| Open emitter | An open emitter logic output. |
| Unconnected | A pin that should not be connected to anything. |