diff --git a/charon_vna/gui.py b/charon_vna/gui.py
index b291b2c..48fba13 100644
--- a/charon_vna/gui.py
+++ b/charon_vna/gui.py
@@ -56,6 +56,9 @@ class MainWindow(QMainWindow):
             vna_kwargs["ip"] = ip
         self.vna = Charon(**vna_kwargs)
 
+        self.active_port = 0
+        self.vna.set_switches(a=self.active_port, b=self.active_port)
+
         mpl.use("QtAgg")
 
         self.setWindowTitle("Charon VNA")
@@ -90,6 +93,9 @@ class MainWindow(QMainWindow):
         action_trigger.triggered.connect(self.capture)
         action_trigger.setShortcut("Ctrl+T")
         menu_stimulus.addAction(action_trigger)
+        action_p0 = QAction("Switch &Port", self)
+        action_p0.triggered.connect(self.toggle_port)
+        menu_stimulus.addAction(action_p0)
 
         menu_calibration = QMenu("&Calibration")
         menubar.addMenu(menu_calibration)
@@ -139,6 +145,11 @@ class MainWindow(QMainWindow):
         widget.setLayout(window_layout)
         self.setCentralWidget(widget)
 
+    def toggle_port(self):
+        self.active_port = int(not self.active_port)
+        print(f"Activating port {self.active_port}")
+        self.vna.set_switches(a=self.active_port, b=self.active_port)
+
     def saveas_config(self) -> None:
         print("Prompting for save path...")
         dialog = QFileDialog(self)
diff --git a/charon_vna/vna.py b/charon_vna/vna.py
index d7c453f..e44f161 100644
--- a/charon_vna/vna.py
+++ b/charon_vna/vna.py
@@ -140,6 +140,8 @@ class Charon:
         self._set_dac_code(value=0, channel=1)
         self._set_dac_code(value=0, channel=2)
 
+        self.set_switches(a=0, b=0)
+
     def get_config(self) -> Dict[str, Any]:
         config = dict()
         config["rx_lo"] = self.sdr.rx_lo
@@ -171,6 +173,18 @@ class Charon:
     def _set_dac_voltage(self, voltage: float, channel: Literal[1, 2]):
         raise NotImplementedError()
 
+    def set_switches(self, a: int, b: int, excitation: int | None = None):
+        if excitation is None:
+            excitation = a
+
+        val = 0
+
+        val |= int(bool(excitation)) << 0  # exc = GPO0
+        val |= int(bool(a)) << 2  # a = GPO2
+        val |= int(bool(b)) << 1  # b = GPO1
+
+        self._set_gpo(val)
+
     def _set_dac_code(
         self,
         value: int,