feat: implement tripad footprint configuration

src/fn/index.ts

@@ -81,3 +81,4 @@ export { sot343 } from "./sot343"
 export { m2host } from "./m2host"
 export { mountedpcbmodule } from "./mountedpcbmodule"
 export { to92l } from "./to92l"
+export { tripad } from "./tripad"

src/fn/tripad.ts

@@ -0,0 +1,117 @@
+import { z } from "zod"
+import { rectpad } from "../helpers/rectpad"
+import { silkscreenRef } from "../helpers/silkscreenRef"
+import type { AnyCircuitElement, PcbSilkscreenPath } from "circuit-json"
+import { base_def } from "../helpers/zod/base_def"
+
+/**
+ * Tripad footprint generator
+ *
+ * A tripad is a 3-pad SMD configuration commonly used for transistors, MOSFETs,
+ * and other 3-terminal devices. It features two smaller signal pads on one side
+ * and a larger pad (often a thermal/tab pad) on the opposite side.
+ *
+ * Default dimensions are based on common tripad footprints found in the wild
+ * (similar to TO-252 / D-PAK style tripad SMD footprints):
+ *   - w: overall width (pad center-to-center X span + pad widths)
+ *   - h: overall height (body height)
+ *   - p: pitch between the two small pads (Y axis)
+ *   - pw: small pad width (X dimension)
+ *   - ph: small pad height (Y dimension)
+ *   - lw: large pad width (X dimension)
+ *   - lh: large pad height (Y dimension)
+ *
+ * Pin numbering (CCW from bottom-left):
+ *   Pin 1: top-left small pad
+ *   Pin 2: large pad (right side) — often drain/tab
+ *   Pin 3: bottom-left small pad
+ *
+ * Example string: "tripad", "tripad_w4_h4_p2.3"
+ */
+export const tripad_def = base_def.extend({
+  fn: z.string(),
+  w: z.string().default("4.7mm"),
+  h: z.string().default("4.0mm"),
+  p: z.string().default("2.3mm"),
+  pw: z.string().default("1.5mm"),
+  ph: z.string().default("1.5mm"),
+  lw: z.string().default("2.5mm"),
+  lh: z.string().default("3.5mm"),
+  string: z.string().optional(),
+})
+
+export const tripad = (
+  raw_params: z.input<typeof tripad_def>,
+): { circuitJson: AnyCircuitElement[]; parameters: any } => {
+  const parameters = tripad_def.parse(raw_params)
+
+  const w = Number.parseFloat(parameters.w)
+  const h = Number.parseFloat(parameters.h)
+  const p = Number.parseFloat(parameters.p)
+  const pw = Number.parseFloat(parameters.pw)
+  const ph = Number.parseFloat(parameters.ph)
+  const lw = Number.parseFloat(parameters.lw)
+  const lh = Number.parseFloat(parameters.lh)
+
+  // Two small pads on the left side, large pad on the right
+  // The span from small pad centers to large pad center equals w/2
+  const smallPadX = -(w / 2 - pw / 2)
+  const largePadX = w / 2 - lw / 2
+
+  const pads: AnyCircuitElement[] = [
+    // Pin 1: top-left small pad
+    rectpad(1, smallPadX, p / 2, pw, ph),
+    // Pin 2: large pad (right side, thermal/tab)
+    rectpad(2, largePadX, 0, lw, lh),
+    // Pin 3: bottom-left small pad
+    rectpad(3, smallPadX, -p / 2, pw, ph),
+  ]
+
+  // Silkscreen outline
+  const silkPadding = 0.2
+  const bodyLeft = smallPadX - pw / 2 - silkPadding
+  const bodyRight = largePadX + lw / 2 + silkPadding
+  const bodyTop = h / 2
+  const bodyBottom = -h / 2
+
+  const silkscreenOutline: PcbSilkscreenPath = {
+    type: "pcb_silkscreen_path",
+    layer: "top",
+    pcb_component_id: "",
+    pcb_silkscreen_path_id: "silkscreen_outline",
+    route: [
+      { x: bodyLeft, y: bodyTop },
+      { x: bodyRight, y: bodyTop },
+      { x: bodyRight, y: bodyBottom },
+      { x: bodyLeft, y: bodyBottom },
+      { x: bodyLeft, y: bodyTop },
+    ],
+    stroke_width: 0.1,
+  }
+
+  // Pin 1 indicator: notch at top-left corner
+  const notchSize = 0.4
+  const pin1Indicator: PcbSilkscreenPath = {
+    type: "pcb_silkscreen_path",
+    layer: "top",
+    pcb_component_id: "",
+    pcb_silkscreen_path_id: "pin1_indicator",
+    route: [
+      { x: bodyLeft, y: bodyTop - notchSize },
+      { x: bodyLeft + notchSize, y: bodyTop },
+    ],
+    stroke_width: 0.1,
+  }
+
+  const silk = silkscreenRef(0, bodyTop + 0.4, 0.3)
+
+  return {
+    circuitJson: [
+      ...pads,
+      silkscreenOutline,
+      pin1Indicator,
+      silk as AnyCircuitElement,
+    ],
+    parameters,
+  }
+}

src/footprinter.ts

@@ -257,6 +257,9 @@ export type Footprinter = {
   solderjumper: (
     num_pins?: number,
   ) => FootprinterParamsBuilder<"bridged" | "p" | "pw" | "ph">
+  tripad: () => FootprinterParamsBuilder<
+    "w" | "h" | "p" | "pw" | "ph" | "lw" | "lh"
+  >
 
   params: () => any
   /** @deprecated use circuitJson() instead */

tests/tripad1.test.ts

@@ -0,0 +1,11 @@
+import { test, expect } from "bun:test"
+import { convertCircuitJsonToPcbSvg } from "circuit-to-svg"
+import { fp } from "../src/footprinter"
+
+test("tripad default", () => {
+  const circuitJson = fp.string("tripad").circuitJson()
+  const pads = circuitJson.filter((e) => e.type === "pcb_smtpad")
+  expect(pads.length).toBe(3)
+  const svgContent = convertCircuitJsonToPcbSvg(circuitJson)
+  expect(svgContent).toMatchSvgSnapshot(import.meta.path, "tripad_default")
+})

tests/tripad2.test.ts

@@ -0,0 +1,14 @@
+import { test, expect } from "bun:test"
+import { convertCircuitJsonToPcbSvg } from "circuit-to-svg"
+import { fp } from "../src/footprinter"
+
+test("tripad custom dimensions", () => {
+  const circuitJson = fp.string("tripad_w5_h4.5_p2.54").circuitJson()
+  const pads = circuitJson.filter((e) => e.type === "pcb_smtpad")
+  expect(pads.length).toBe(3)
+  const svgContent = convertCircuitJsonToPcbSvg(circuitJson)
+  expect(svgContent).toMatchSvgSnapshot(
+    import.meta.path,
+    "tripad_custom_dimensions",
+  )
+})

tests/tripad3.test.ts

@@ -0,0 +1,36 @@
+import { test, expect } from "bun:test"
+import { tripad } from "../src/fn/tripad"
+
+test("tripad pin numbering", () => {
+  const result = tripad({ fn: "tripad" })
+  const pads = result.circuitJson.filter((e) => e.type === "pcb_smtpad")
+  expect(pads.length).toBe(3)
+
+  // Pin 1 is top-left small pad (highest y)
+  const pin1 = pads.find(
+    (e) => e.type === "pcb_smtpad" && e.port_hints?.includes("1"),
+  )
+  const pin2 = pads.find(
+    (e) => e.type === "pcb_smtpad" && e.port_hints?.includes("2"),
+  )
+  const pin3 = pads.find(
+    (e) => e.type === "pcb_smtpad" && e.port_hints?.includes("3"),
+  )
+
+  expect(pin1).toBeDefined()
+  expect(pin2).toBeDefined()
+  expect(pin3).toBeDefined()
+
+  // Pin 1 and 3 are on the left (negative x), pin 2 is on the right (positive x)
+  if (pin1 && pin2 && pin3) {
+    expect((pin1 as any).x).toBeLessThan((pin2 as any).x)
+    expect((pin3 as any).x).toBeLessThan((pin2 as any).x)
+    // Pin 1 is above pin 3
+    expect((pin1 as any).y).toBeGreaterThan((pin3 as any).y)
+    // Pin 2 (large pad) is centered vertically
+    expect((pin2 as any).y).toBe(0)
+    // Large pad is bigger than small pads
+    expect((pin2 as any).width).toBeGreaterThan((pin1 as any).width)
+    expect((pin2 as any).height).toBeGreaterThan((pin1 as any).height)
+  }
+})

tests/tripad4.test.ts

@@ -0,0 +1,11 @@
+import { test, expect } from "bun:test"
+import { convertCircuitJsonToPcbSvg } from "circuit-to-svg"
+import { tripad } from "../src/fn/tripad"
+
+test("tripad direct call with custom params", () => {
+  const result = tripad({ fn: "tripad", w: "6mm", h: "5mm", p: "3mm" })
+  const pads = result.circuitJson.filter((e) => e.type === "pcb_smtpad")
+  expect(pads.length).toBe(3)
+  const svgContent = convertCircuitJsonToPcbSvg(result.circuitJson)
+  expect(svgContent).toMatchSvgSnapshot(import.meta.path, "tripad_custom_call")
+})