Virtual Pins Reference

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

---

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.

---

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
}

---

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
}

---

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

---

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.)

---

Digital and analog pins (D / A prefix)

In addition to virtual pins, VWire supports addressing physical hardware pins directly using D-prefixed (digital) and A-prefixed (analog) pin names.

Pin prefix	Example	Description
D0–D99	D2, D13	Digital GPIO — reads or writes 0/1, or PWM (2–255)
A0–A15	A0, A1	Analog ADC input — reads raw ADC value
V0–V255	V0, V5	Virtual pin — arbitrary data, no hardware mapping

Physical pin names map directly to the labels printed on your development board:

• D4 on an ESP8266/NodeMCU board refers to the pin labeled D4, which is hardware GPIO 2
• D4 on an ESP32 board refers to GPIO 4

The library resolves these mappings automatically — you never need to look up GPIO numbers.

When to use virtual pins vs physical pins

Scenario	Use
Sensor value (temperature, humidity, ADC)	V0–V255 (virtual)
Computed / formatted value	Virtual
Control a relay, LED, buzzer directly	D-pin via GPIO manager
Read a button or switch state directly	D-pin via GPIO manager
Read a potentiometer or analog sensor	A-pin via GPIO manager
Multiple values per update (CSV)	Virtual

Physical pins are managed by the GPIO Pin Manager feature. See GPIO Pin Manager for setup and usage.