Virtual Pins Reference

Virtual pins (V0–V255) are the data channels between your firmware and your dashboard widgets.

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Sending data to the dashboard

Call virtualSend inside your loop() at whatever interval makes sense for your sensor:

// Send a float
Vwire.virtualSend(V0, temperature);

// Send an integer
Vwire.virtualSend(V1, humidity);

// Send a formatted string
Vwire.virtualSend(V2, String(speed, 1) + " km/h");

// Send multiple values (CSV) — used by MAP widget
Vwire.virtualSend(V3, String(lat, 6) + "," + String(lon, 6));

Rate limiting

VWire will throttle extreme write rates. Sending data every 100–2000 ms is appropriate for most sensors.

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Receiving commands from the dashboard

Register a handler for pins that widgets write back to (e.g. a Button or Switch):

VWIRE_RECEIVE(V5) {
  int value = param.asInt();
  digitalWrite(RELAY_PIN, value);          // 1 = on, 0 = off
  Vwire.virtualSend(V5, value);           // echo back current state
}

VWIRE_RECEIVE(V6) {
  int brightness = param.asInt();
  analogWrite(LED_PIN, brightness);        // 0–255 from a Slider
}

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Reading pin state on connect

To restore state after a device reboots, sync the current server-side value in setup():

void setup() {
  Vwire.begin(SSID, PASSWORD);

  // Request current value from server
  Vwire.syncVirtual(V5);  // will trigger VWIRE_RECEIVE(V5) with current value
}

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Data types

All values travel as strings over MQTT. The library provides helpers:

Method	Returns
param.asStr()	const char*
param.asInt()	int
param.asFloat()	float
param.asDouble()	double

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Pin assignment tips

Range	Suggested use
V0–V9	Primary sensor readings
V10–V19	Secondary / computed values
V20–V29	Control outputs (relays, PWM)
V100–V109	GPS / location data
V200–V255	Metadata (heap, RSSI, IP, etc.)