<fanout />

Overview

<fanout /> groups components for escape routing: tscircuit routes their connections to exits, then connects those exits to the rest of the board. It is an alias of <breakout /> and accepts the same props. Like a breakout, it does not create a subcircuit, selector scope, or private net scope. Components inside it remain accessible through selectors such as R1.1.

Automatic fanout

Place the components to escape inside <fanout /> and define their electrical connections with <trace />. The default fanout autorouter generates exits for connections leaving the region. Use padding to give those routes room around the component pads.

export default () => (
  <board width="20mm" height="16mm">
    <fanout name="R1_FANOUT" padding="2mm">
      <resistor name="R1" resistance="1k" footprint="0402" pcbX={0} pcbY={0} />
    </fanout>
    <resistor name="R2" resistance="1k" footprint="0402" pcbX={7} pcbY={0} />
    <trace name="SIGNAL" from="R1.1" to="R2.1" />
  </board>
)

For explicit exit locations, place a <fanoutpoint /> inside the fanout. It is an alias of <breakoutpoint />, with the same connection, pcbX, and pcbY props.

Reuse saved routes

Pass pcbTracePaths to reuse pre-generated wire and via routes instead of automatically routing the fanout. Each entry identifies a component port with connection and supplies its port-to-exit route:

<fanout name="SAVED_FANOUT" pcbTracePaths={savedPaths}>
  <resistor name="R1" resistance="1k" footprint="0402" />
</fanout>

Saved coordinates use the fanout's local PCB frame. Core creates an exit at the end of each path and preserves the supplied copper during global routing. Keep the electrical <trace /> connections and supply paths for every routing connection in the fanout. Do not add an explicit exit for a port already covered by a saved path.

Routes may start or end with vias. A via at the starting pad requires allowViaInPad: true in the board or fanout autorouter configuration. See Reusing saved fanout trace paths for a complete example, JSON imports, version requirements, and validation rules.

Properties

<fanout /> accepts the layout props of <group />, plus the routing props shared with <breakout />:

Property	Description
padding	Space around the fanout region.
paddingLeft / paddingRight / paddingTop / paddingBottom	Set padding on individual sides.
autorouter	Escape router or configuration. Defaults to fanout.
pcbTracePaths	Saved port-to-exit wire/via routes covering all routing connections in the fanout.
busFanoutDirections	Maps named buses to preferred escape directions.
fanoutBoundaryPadding	Padding between source pads and the shared boundary where fanout traces terminate.
fanoutRoutingLayers	Copper layers available to boundary-terminated fanout buses.
fanoutPourNetMap	Maps plane layers to nets for source-only escapes; inferred from matching copper pours when omitted.

For bus direction and power-plane examples, see the breakout reference. For a larger workflow with layer planning and skew constraints, see Routing DDR.