Add SHT31 temp/humidity sensor (#101)

examples/sht31_example.cpp

@@ -0,0 +1,51 @@
+// SHT31_example.cpp
+
+#include <Arduino.h>
+
+//#define SERIAL_DEBUG_DISABLED
+
+#define USE_LIB_WEBSOCKET true
+
+#include "sensesp_app.h"
+#include "signalk/signalk_output.h"
+#include "sensors/sht31.h"
+
+ReactESP app([] () {
+  #ifndef SERIAL_DEBUG_DISABLED
+  Serial.begin(115200);
+
+  // A small arbitrary delay is required to let the
+  // serial port catch up
+
+  delay(100);
+  Debug.setSerialEnabled(true);
+  #endif
+
+  // true will disable systemHz, freemem, uptime, and ipaddress "sensors"
+  bool disableStandardSensors = false;
+
+  sensesp_app = new SensESPApp(disableStandardSensors);
+
+  // Create a SHT31, which represents the physical sensor.
+  // 0x44 is the default address. Some chips use 0x45, which is shown here.
+  auto* pSHT31 = new SHT31(0x45);
+
+
+  // Define the read_delay you're going to use. The default is 500 ms.
+  const uint read_delay = 1000;
+
+  // Create a SHT31value, which is used to read a specific value from the SHT31, and send its output
+  // to SignalK as a Number (float). This one is for the temperature reading.
+  auto* pSHT31temperature = new SHT31value(pSHT31, temperature, read_delay, "fridge/temperature");
+
+        pSHT31temperature->connectTo(new SKOutputNumber("environment.inside.refrigerator.temperature"));
+
+
+  // Do the same for the humidity value.
+  auto* pSHT31humidity = new SHT31value(pSHT31, humidity,  read_delay, "fridge/humidity");
+
+        pSHT31humidity->connectTo(new SKOutputNumber("environment.inside.refrigerator.humidity"));
+
+
+  sensesp_app->enable();
+});

platformio.ini

@@ -40,6 +40,7 @@ lib_deps =
     Wire
     Adafruit BME280 Library
     Adafruit BMP280 Library
+    Adafruit SHT31 Library
 
 extra_scripts = extra_script.py
 

src/sensors/sht31.cpp

@@ -0,0 +1,71 @@
+#include "sht31.h"
+
+#include "sensesp.h"
+#include <RemoteDebug.h>
+
+
+// SHT31 represents an ADAfruit (or compatible) SHT31 temperature & humidity sensor.
+SHT31::SHT31(uint8_t addr, String config_path) :
+       Sensor(config_path), addr{addr} {
+    className = "SHT31";
+    load_configuration();
+    pAdafruitSHT31 = new Adafruit_SHT31();
+    if (!pAdafruitSHT31->begin(addr)) {
+       debugE("Could not find a valid SHT31 sensor: check address and wiring");
+    }
+}
+
+
+// SHT31value reads and outputs the specified type of value of a SHT31 sensor
+SHT31value::SHT31value(SHT31* pSHT31, SHT31ValType val_type, uint read_delay, String config_path) :
+                   NumericSensor(config_path), pSHT31{pSHT31}, val_type{val_type}, read_delay{read_delay} {
+      className = "SHT31value";
+      load_configuration();
+}
+
+// SHT31 outputs temp in Celsius. Need to convert to Kelvin before sending to Signal K.
+// Humidity is output in relative humidity (0 - 100%)
+void SHT31value::enable() {
+  app.onRepeat(read_delay, [this](){ 
+      if (val_type == temperature) {
+          output = pSHT31->pAdafruitSHT31->readTemperature() + 273.15; // Kelvin is Celsius + 273.15
+      }
+      else if (val_type == humidity) {
+          output = pSHT31->pAdafruitSHT31->readHumidity();
+      }
+      else output = 0.0;
+
+      notify();
+ });
+}
+
+JsonObject& SHT31value::get_configuration(JsonBuffer& buf) {
+  JsonObject& root = buf.createObject();
+  root["read_delay"] = read_delay;
+  root["value"] = output;
+  return root;
+  };
+
+  static const char SCHEMA[] PROGMEM = R"###({
+    "type": "object",
+    "properties": {
+        "read_delay": { "title": "Read delay", "type": "number", "description": "The time, in milliseconds, between each read of the input" },
+        "value": { "title": "Last value", "type" : "number", "readOnly": true }
+    }
+  })###";
+
+
+  String SHT31value::get_config_schema() {
+  return FPSTR(SCHEMA);
+}
+
+bool SHT31value::set_configuration(const JsonObject& config) {
+  String expected[] = {"read_delay"};
+  for (auto str : expected) {
+    if (!config.containsKey(str)) {
+      return false;
+    }
+  }
+  read_delay = config["read_delay"];
+  return true;
+}

src/sensors/sht31.h

@@ -0,0 +1,45 @@
+#ifndef _sht31_H_
+#define _sht31_H_
+
+#include <Wire.h>
+#include <Adafruit_SHT31.h>
+
+#include "sensor.h"
+
+// The SHT31 classes are based on the ADAfruit_SHT31 library.
+
+// SHT31 represents an ADAfruit (or compatible) SHT31 temperature & humidity sensor.
+// The constructor creates a pointer to the instance, and starts up the sensor. The pointer is
+// passed to SHT31value, which retrieves the specified value.
+
+class SHT31 : public Sensor {
+  public:
+    SHT31(uint8_t addr = 0x44, String config_path = "");
+    Adafruit_SHT31* pAdafruitSHT31;
+
+  private:
+    uint8_t addr;
+};
+
+
+// Pass one of these in the constructor to SHT31value() to tell which type of value you want to output
+enum SHT31ValType { temperature, humidity };
+
+// SHT31value reads and outputs the specified value of a SHT31 sensor.
+class SHT31value : public NumericSensor {
+  public:
+    SHT31value(SHT31* pSHT31, SHT31ValType val_type, uint read_delay = 500, String config_path="");
+    void enable() override final;
+    SHT31* pSHT31;
+
+  private:
+
+    SHT31ValType val_type;
+    uint read_delay;
+    virtual JsonObject& get_configuration(JsonBuffer& buf) override;
+    virtual bool set_configuration(const JsonObject& config) override;
+    virtual String get_config_schema() override;
+
+};
+
+#endif