tools: add car porting example notebook (#30918)

* add car porting example notebooks

* not required

tools/car_porting/examples/subaru_steer_temp_fault.ipynb

@@ -0,0 +1,114 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# An example of searching through the database of segments for a specific condition, and plotting the results.\n",
+    "\n",
+    "segments = [\n",
+    "  \"c3d1ccb52f5f9d65|2023-07-22--01-23-20--6\",\n",
+    "  \"c3d1ccb52f5f9d65|2023-07-22--01-23-20--7\",\n",
+    "  \"c3d1ccb52f5f9d65|2023-07-22--01-23-20--8\",\n",
+    "]\n",
+    "platform = \"SUBARU OUTBACK 6TH GEN\""
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import copy\n",
+    "import matplotlib.pyplot as plt\n",
+    "import numpy as np\n",
+    "from openpilot.tools.lib.logreader import logreader_from_route_or_segment\n",
+    "\n",
+    "\n",
+    "from selfdrive.car.subaru.values import CanBus, DBC\n",
+    "\n",
+    "from opendbc.can.parser import CANParser\n",
+    "\n",
+    "\"\"\"\n",
+    "In this example, we search for positive transitions of Steer_Warning, which indicate that the EPS\n",
+    "has stopped responding to our messages. This analysis would allow you to find the cause of these\n",
+    "steer warnings and potentially work around them.\n",
+    "\"\"\"\n",
+    "\n",
+    "for segment in segments:\n",
+    "  print(segment)\n",
+    "  lr = logreader_from_route_or_segment(segment)\n",
+    "\n",
+    "  can_msgs = [msg for msg in lr if msg.which() == \"can\"]\n",
+    "\n",
+    "  messages = [\n",
+    "    (\"Steering_Torque\", 50)\n",
+    "  ]\n",
+    "\n",
+    "  cp = CANParser(DBC[platform][\"pt\"], messages, CanBus.main)\n",
+    "\n",
+    "  steering_torque_history = []\n",
+    "  examples = []\n",
+    "\n",
+    "  for msg in can_msgs:\n",
+    "    cp.update_strings([msg.as_builder().to_bytes()])\n",
+    "    steering_torque_history.append(copy.copy(cp.vl[\"Steering_Torque\"]))\n",
+    "  \n",
+    "  steer_warning_last = False\n",
+    "  for i, steering_torque_msg in enumerate(steering_torque_history):\n",
+    "    steer_warning = steering_torque_msg[\"Steer_Warning\"]\n",
+    "\n",
+    "    steer_angle = steering_torque_msg[\"Steering_Angle\"]\n",
+    "\n",
+    "    if steer_warning and not steer_warning_last: # positive transition of \"Steer_Warning\"\n",
+    "      examples.append(i)\n",
+    "\n",
+    "    steer_warning_last = steer_warning\n",
+    "\n",
+    "  FRAME_DELTA = 100 # plot this many frames around the positive transition\n",
+    "\n",
+    "  for example in examples:\n",
+    "    fig, axs = plt.subplots(2)\n",
+    "\n",
+    "    min_frame = int(example-FRAME_DELTA/2)\n",
+    "    max_frame = int(example+FRAME_DELTA/2)\n",
+    "\n",
+    "    steering_angle_history = [msg[\"Steering_Angle\"] for msg in steering_torque_history[min_frame:max_frame]]\n",
+    "    steering_warning_history = [msg[\"Steer_Warning\"] for msg in steering_torque_history[min_frame:max_frame]]\n",
+    "\n",
+    "    xs = np.arange(-FRAME_DELTA/2, FRAME_DELTA/2)\n",
+    "\n",
+    "    axs[0].plot(xs, steering_angle_history)\n",
+    "    axs[0].set_ylabel(\"Steering Angle (deg)\")\n",
+    "    axs[1].plot(xs, steering_warning_history)\n",
+    "    axs[1].set_ylabel(\"Steer Warning\")\n",
+    "\n",
+    "    plt.show()\n"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.11.4"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}