feat: add DRC check to prevent I2C SDA and SCL from connecting

index.ts

@@ -9,4 +9,5 @@ export { checkSourceTracesHavePcbTraces } from "./lib/check-source-traces-have-p
 export { checkPcbTracesOutOfBoard } from "./lib/check-trace-out-of-board/checkTraceOutOfBoard"
 export { checkPcbComponentOverlap } from "./lib/check-pcb-components-overlap/checkPcbComponentOverlap"
 export { checkPinMustBeConnected } from "./lib/check-pin-must-be-connected"
+export { checkI2cSdaConnectedToSclMisconfigured } from "./lib/check-i2c-sda-connected-to-scl"
 export { runAllChecks } from "./lib/run-all-checks"

lib/check-i2c-sda-connected-to-scl.ts

@@ -0,0 +1,87 @@
+import type {
+  AnyCircuitElement,
+  SourceI2cMisconfiguredError,
+} from "circuit-json"
+import { getSourcePortConnectivityMapFromCircuitJson } from "circuit-json-to-connectivity-map"
+
+type SourceComponent = Extract<
+  AnyCircuitElement,
+  { source_component_id: string; name: string }
+>
+
+export function checkI2cSdaConnectedToSclMisconfigured(
+  circuitJson: AnyCircuitElement[],
+): SourceI2cMisconfiguredError[] {
+  const errors: SourceI2cMisconfiguredError[] = []
+
+  const sourceComponents = circuitJson.filter(
+    (el): el is SourceComponent =>
+      "source_component_id" in el &&
+      (el.type === "source_component" || el.type.startsWith("source_simple_")),
+  )
+
+  // Get all source ports to easily look up their attributes
+  const sourcePorts = circuitJson.filter(
+    (el): el is Extract<AnyCircuitElement, { type: "source_port" }> =>
+      el.type === "source_port",
+  )
+  const portMap = new Map(sourcePorts.map((p) => [p.source_port_id, p]))
+
+  const connMap = getSourcePortConnectivityMapFromCircuitJson(circuitJson)
+
+  for (const [netId, connectedPortIds] of Object.entries(connMap.netMap)) {
+    let hasSda = false
+    let hasScl = false
+
+    const conflictingPortIds: string[] = []
+
+    for (const portId of connectedPortIds) {
+      const port = portMap.get(portId)
+      if (!port) continue
+
+      let shouldAddPort = false
+      if (port.is_configured_for_i2c_sda) {
+        hasSda = true
+        shouldAddPort = true
+      }
+      if (port.is_configured_for_i2c_scl) {
+        hasScl = true
+        shouldAddPort = true
+      }
+      if (shouldAddPort && !conflictingPortIds.includes(portId)) {
+        conflictingPortIds.push(portId)
+      }
+    }
+
+    if (hasSda && hasScl) {
+      // Sort conflicting port IDs to ensure deterministic ID generation
+      const sortedConflicts = [...conflictingPortIds].sort()
+      const conflictIdStr = sortedConflicts.join("_")
+
+      const portDetails = sortedConflicts.map((portId) => {
+        const port = portMap.get(portId)
+        const component = sourceComponents.find(
+          (c) => c.source_component_id === port?.source_component_id,
+        )
+        const componentName = component?.name ?? "Unknown"
+        const portName = port?.name ?? "Unknown"
+        const i2cRole = port?.is_configured_for_i2c_sda
+          ? "I2C SDA"
+          : port?.is_configured_for_i2c_scl
+            ? "I2C SCL"
+            : "Unknown"
+        return `${componentName}.${portName} (${i2cRole})`
+      })
+
+      errors.push({
+        type: "source_i2c_misconfigured_error",
+        source_i2c_misconfigured_error_id: `source_i2c_misconfigured_error_${conflictIdStr}`,
+        error_type: "source_i2c_misconfigured_error",
+        message: `${portDetails.join(" is connected to ")} on the same net. To fix this, ensure SDA and SCL are routed to separate nets.`,
+        source_port_ids: conflictingPortIds,
+      })
+    }
+  }
+
+  return errors
+}

lib/run-all-checks.ts

@@ -9,6 +9,7 @@ import { checkSourceTracesHavePcbTraces } from "./check-source-traces-have-pcb-t
 import { checkPcbTracesOutOfBoard } from "./check-trace-out-of-board/checkTraceOutOfBoard"
 import { checkPcbComponentOverlap } from "./check-pcb-components-overlap/checkPcbComponentOverlap"
 import { checkPinMustBeConnected } from "./check-pin-must-be-connected"
+import { checkI2cSdaConnectedToSclMisconfigured } from "./check-i2c-sda-connected-to-scl"
 import type { AnyCircuitElement } from "circuit-json"
 
 export async function runAllChecks(circuitJson: AnyCircuitElement[]) {
@@ -24,5 +25,6 @@ export async function runAllChecks(circuitJson: AnyCircuitElement[]) {
     ...checkPcbTracesOutOfBoard(circuitJson),
     ...checkPcbComponentOverlap(circuitJson),
     ...checkPinMustBeConnected(circuitJson),
+    ...checkI2cSdaConnectedToSclMisconfigured(circuitJson),
   ]
 }

package.json

@@ -19,18 +19,18 @@
     "@types/bun": "^1.2.8",
     "@types/debug": "^4.1.12",
     "bun-match-svg": "^0.0.11",
+    "circuit-json": "^0.0.387",
     "circuit-to-svg": "^0.0.166",
-    "circuit-json": "^0.0.380",
     "debug": "^4.3.5",
     "tscircuit": "^0.0.525",
-    "zod": "^3.23.8",
-    "tsup": "^8.2.3"
+    "tsup": "^8.2.3",
+    "zod": "^3.23.8"
   },
   "peerDependencies": {
+    "@flatten-js/core": "*",
     "circuit-json": "*",
     "@tscircuit/math-utils": "*",
     "circuit-json-to-connectivity-map": "*",
-    "@flatten-js/core": "*",
     "typescript": "^5.5.3"
   }
-}
+}

tests/lib/check-i2c-sda-connected-to-scl.test.ts

@@ -0,0 +1,71 @@
+import { expect, test } from "bun:test"
+import { checkI2cSdaConnectedToSclMisconfigured } from "../../lib/check-i2c-sda-connected-to-scl"
+import type { AnyCircuitElement } from "circuit-json"
+
+test("checkI2cSdaConnectedToSclMisconfigured detects SDA connected to SCL", () => {
+  const circuitJson: AnyCircuitElement[] = [
+    {
+      type: "source_port",
+      source_port_id: "port_sda",
+      name: "SDA",
+      is_configured_for_i2c_sda: true,
+      source_component_id: "comp_1",
+    },
+    {
+      type: "source_component",
+      source_component_id: "comp_1",
+      name: "U1",
+    },
+    {
+      type: "source_port",
+      source_port_id: "port_scl",
+      name: "SCL",
+      is_configured_for_i2c_scl: true,
+      source_component_id: "comp_2",
+    },
+    {
+      type: "source_component",
+      source_component_id: "comp_2",
+      name: "U2",
+    },
+    {
+      type: "source_trace",
+      source_trace_id: "trace_1",
+      connected_source_port_ids: ["port_sda", "port_scl"],
+      connected_source_net_ids: [],
+    },
+  ] as AnyCircuitElement[]
+
+  const errors = checkI2cSdaConnectedToSclMisconfigured(circuitJson)
+  expect(errors).toHaveLength(1)
+  expect(errors[0].message).toEqual(expect.stringContaining("U2.SCL (I2C SCL)"))
+  expect(errors[0].message).toEqual(expect.stringContaining("U1.SDA (I2C SDA)"))
+  expect(errors[0].source_port_ids).toContain("port_sda")
+  expect(errors[0].source_port_ids).toContain("port_scl")
+})
+
+test("checkI2cSdaConnectedToSclMisconfigured allows SDA connected to SDA", () => {
+  const circuitJson: AnyCircuitElement[] = [
+    {
+      type: "source_port",
+      source_port_id: "port_sda1",
+      name: "SDA1",
+      is_configured_for_i2c_sda: true,
+    },
+    {
+      type: "source_port",
+      source_port_id: "port_sda2",
+      name: "SDA2",
+      is_configured_for_i2c_sda: true,
+    },
+    {
+      type: "source_trace",
+      source_trace_id: "trace_1",
+      connected_source_port_ids: ["port_sda1", "port_sda2"],
+      connected_source_net_ids: [],
+    },
+  ] as AnyCircuitElement[]
+
+  const errors = checkI2cSdaConnectedToSclMisconfigured(circuitJson)
+  expect(errors).toHaveLength(0)
+})