From 4f36a1654ff6560c915a39e1f9999e0efc4a9680 Mon Sep 17 00:00:00 2001
From: Tanner Robison <Robison.tnr@gmail.com>
Date: Tue, 7 Jul 2026 20:48:28 -0700
Subject: SPICE model in the loop testing

---
 MIL_testing/spice_backend.py | 70 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 MIL_testing/spice_backend.py

(limited to 'MIL_testing/spice_backend.py')

diff --git a/MIL_testing/spice_backend.py b/MIL_testing/spice_backend.py
new file mode 100644
index 0000000..674ae30
--- /dev/null
+++ b/MIL_testing/spice_backend.py
@@ -0,0 +1,70 @@
+import subprocess
+import re
+
+class SpiceBackend:
+    """This is what actually does all of the spice stuff"""
+    def __init__(self, device_file: str):
+        self.conductance = 0
+        self.voltage = 0
+        self.current = 0
+        self.time = 0
+
+    def simulate(self, voltage_signal: float, return_current: bool = False) -> float:
+        """runs the simulation for one time step"""
+        len_voltage_signal = 1
+        try:
+            len_voltage_signal = len(voltage_signal)
+        except:
+            voltage_signal = [voltage_signal]
+
+        if return_current:
+            current = np.zeros(len_voltage_signal)
+
+        for t in enumerate(len_voltage_signal):
+            result = self.run_spice(voltage_signal)
+
+            single_current = result.current
+            self.conductance = result.conductance
+
+            if return_current:
+                current[t] = single_current
+
+        if return_current:
+            return current
+
+
+    def set_conductance(self, conductance: float):
+        """Handled by spice now"""
+        """Could probably still add some safety checks just to be sure later"""
+        self.conductance = conductance
+
+    def run_spice(self, voltage: float) -> float:
+        """returns the current after given a voltage signal"""
+        #need to find a way to pass voltage signal to ngspice here
+        #also maybe a time series resolution??
+        result = subprocess.run(
+                ["ngspice" "-b" "spicefile.cir"],
+                capture_output=True,
+                text=True
+        )
+        if result.returncode != 0:
+            raise RuntimeError(result.stderr)
+
+        # parse current into float variable
+        output = result.stdout
+        #is there a better (less rigid) way of grabbing the output
+        current_match = re.search("final_current = ([-\deE.+]+)", output)
+        if current_match is None:
+            raise RuntimeError("Could not find current in ngspice output")
+
+        current = float(current_match.group(1))
+
+        if abs(voltage) > 1e-12:
+            conductance = current / voltage
+        else:
+            conductance = self.conductance
+
+        return {
+                "current": current,
+                "conductance": conductance,
+        }
-- 
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