---

name: sensesp-expert description: SensESP development expertise for ESP32/ESP8266 sensors with SignalK integration. Use when developing SensESP firmware (C++/PlatformIO), creating sensor pipelines (producers, transforms, consumers), connecting to SignalK servers, working with ESP32 GPIO, or debugging embedded sensor code. Covers ReactESP async patterns, WiFi configuration, and hardware interfacing.

SensESP Expert

Expertise for developing ESP32/ESP8266 sensors that publish to SignalK.

Quick Reference

Project Structure

my-sensor/
├── platformio.ini      # Build config, dependencies
├── src/
│   └── main.cpp        # Application code
├── include/            # Header files
└── data/               # SPIFFS (web UI)

Basic Application

#include <Arduino.h>
#include "sensesp_app_builder.h"
#include "sensesp/sensors/analog_input.h"
#include "sensesp/transforms/linear.h"

using namespace sensesp;

SensESPApp* sensesp_app;

void setup() {
  SensESPAppBuilder builder;
  sensesp_app = builder
    .set_hostname("my-sensor")
    .set_sk_server("192.168.1.100", 3000)
    .get_app();

  // Sensor pipeline: Producer -> Transform -> Consumer
  auto* input = new AnalogInput(36, 1000);  // GPIO36, 1s interval

  input
    ->connect_to(new Linear(1.0, 0.0, "/transforms/cal"))
    ->connect_to(new SKOutputFloat("environment.outside.temperature"));

  sensesp_app->start();
}

void loop() {
  sensesp_app->tick();
}

Core Pipeline Pattern

Producer → Transform → Transform → Consumer
   ↓           ↓           ↓          ↓
Sensor    Calibrate    Filter    SKOutput

Everything connects via ->connect_to().

Common Producers

new AnalogInput(gpio, interval_ms)              // ADC reading
new DigitalInputState(gpio, mode, interval_ms)  // HIGH/LOW
new DigitalInputCounter(gpio, mode, edge, ms)   // Pulse count
new OneWireTemperature(dallas, config_path)     // DS18B20

Common Transforms

new Linear(multiplier, offset, config_path)     // y = mx + b
new MovingAverage(samples, config_path)         // Smoothing
new ChangeFilter(min, max, skips, config_path)  // Only on change
new Frequency(1.0, config_path)                 // Pulses to Hz
new LambdaTransform<In, Out>([](In v) { return v * 2; }, path)

Consumers (SignalK Output)

new SKOutputFloat("path.to.value", config_path)
new SKOutputInt("path.to.value", config_path)
new SKOutputBool("path.to.value", config_path)

ReactESP Timing (Non-blocking)

// One-shot delay
reactESP->onDelay(5000, []() { /* after 5s */ });

// Repeating
reactESP->onRepeat(500, []() { /* every 500ms */ });

Critical: Never use delay() in loop - use ReactESP instead.

Build Commands

pio run                    # Build
pio run -t upload          # Flash to ESP32
pio device monitor         # Serial output
pio run -t clean           # Clean build

Detailed References

• references/producers.md - All sensor input types
• references/transforms.md - Data processing transforms
• references/patterns.md - C++ coding patterns, class structure
• references/platformio.md - Build configuration, GPIO reference
• references/debugging.md - Logging, serial monitor, common issues

Key Documentation

Resource	URL
SensESP Docs	https://signalk.org/SensESP/
GitHub	https://github.com/SignalK/SensESP
Examples	https://github.com/SignalK/SensESP/tree/main/examples
Class Reference	https://signalk.org/SensESP/docs/generated/docs/