Initial CAN Physical Layer spec

2026-09-11 19:24:15 +02:00
parent f8d111ef5c
commit f97a2c6a6c
8 changed files with 394 additions and 8 deletions
@@ -0,0 +1,132 @@
+{
+  "title": "Vehicle CAN FD topology",
+  "source": "IO_MODULES/CAN_PHYSICAL_LAYER.md: Topology, termination, and service access",
+  "nodes": {
+    "title": {
+      "label": "Vehicle CAN FD \u00b7 continuous linear trunk",
+      "bounds": [
+        30,
+        20,
+        1100,
+        45
+      ]
+    },
+    "subtitle": {
+      "label": "500 kbit/s arbitration  \u00b7  2 Mbit/s data phase  \u00b7  approximately 2\u20132.5 m end-to-end",
+      "bounds": [
+        30,
+        75,
+        1100,
+        40
+      ]
+    },
+    "rear": {
+      "label": "Rear endpoint\n120 \u03a9 across CAN_H / CAN_L",
+      "bounds": [
+        30,
+        170,
+        290,
+        105
+      ]
+    },
+    "ecu": {
+      "label": "ECU \u00b7 local PCB junction\nMid-bus connection",
+      "bounds": [
+        440,
+        170,
+        280,
+        105
+      ]
+    },
+    "front": {
+      "label": "Front endpoint\n120 \u03a9 across CAN_H / CAN_L",
+      "bounds": [
+        840,
+        170,
+        290,
+        105
+      ]
+    },
+    "distance1": {
+      "label": "0.5\u20131 m",
+      "bounds": [
+        320,
+        130,
+        120,
+        40
+      ]
+    },
+    "distance2": {
+      "label": "1\u20131.5 m",
+      "bounds": [
+        720,
+        130,
+        120,
+        40
+      ]
+    },
+    "ecu_note": {
+      "label": "ECU transceiver joins locally on PCB.\nOptional ECU 120 \u03a9 termination: OPEN in V1;\nenable only if the ECU becomes an endpoint.",
+      "bounds": [
+        340,
+        305,
+        710,
+        90
+      ]
+    },
+    "service": {
+      "label": "Debug / service connector\nCAN_H \u00b7 CAN_L \u00b7 CAN_0V\nVery short PCB branch\nNo termination",
+      "bounds": [
+        440,
+        480,
+        350,
+        110
+      ]
+    },
+    "busport": {
+      "label": "Same local ECU bus",
+      "bounds": [
+        60,
+        490,
+        270,
+        80
+      ]
+    },
+    "foot": {
+      "label": "Lines above represent the CAN_H / CAN_L twisted pair, not individual conductors.\nAll nodes also share the defined CAN_0V reference. Avoid a long attached service cable.",
+      "bounds": [
+        30,
+        625,
+        1100,
+        55
+      ]
+    }
+  },
+  "connections": [
+    {
+      "from": "rear",
+      "to": "ecu",
+      "label": ""
+    },
+    {
+      "from": "ecu",
+      "to": "front",
+      "label": ""
+    },
+    {
+      "from": "busport",
+      "to": "service",
+      "label": ""
+    }
+  ],
+  "continuations": {
+    "busport": "ecu"
+  },
+  "bus_model": "Each trunk line represents the differential CAN_H/CAN_L pair. CAN_0V is a separate shared reference.",
+  "termination": {
+    "rear": "120 ohm across CAN_H/CAN_L",
+    "front": "120 ohm across CAN_H/CAN_L",
+    "ecu": "120 ohm option, solder jumper normally open; endpoint use only",
+    "service": "none"
+  }
+}