Initial commit

README.md

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+# Sensirion SCD30 CO2 sensor MQTT gateway for Home Assistant
+
+## Overview
+
+This gateway can be used to publish measurements SCD30 to mqtt.
+
+It supports Home Assistant MQTT Discovery but can also be used without Home Assistant.
+
+Only requirement is MQTT Broker to connect to.
+
+## Example usecase
+
+Attach SCD30 to Raspberry Pi Zero W I2C bus and run this gateway to publish CO2, temperature and humidity to Home Assistant.
+
+## Configuration
+
+Application is configure with environment variables
+
+| variable        | required | default | description |
+|-----------------|:--------:|---------|-------------|
+| SCD30_MQTT_URL        |    x     |         | mqtt url, for example tcp://10.1.2.3:8883 |
+| SCD30_MQTT_USER       |          |         | mqtt username |
+| SCD30_MQTT_PASSWORD   |          |         | mqtt password |
+| SCD30_MQTT_CLIENT_ID  |          | scd30   | mqtt client id |
+| SCD30_DEBUG           |          | false   | enable debug output, true/false |
+| SCD30_ID              |          | scd30   | home assistant discovery id |
+| SCD30_TEMP_OFFSET     |          | 150     | temperature compensation offset |
+| SCD30_NAME            |          | SCD30   | home assistant device name |
+| SCD30_INTEVAL         |          | 50      | measurement interval in seconds |
+
+## Usage
+
+For example with following script
+```sh
+#!/bin/sh
+
+# Change to your real mqtt url
+export MQTT_URL=tcp://localhost:8883
+
+./scd30-mqtt
+```
+
+## MQTT Topics used
+
+- homeassistant/status subscribe to HA status changes
+- scd30/_id_/co2 publish co2
+- scd30/_id_/temperature publish temperature
+- scd30/_id_/humidity publish humidity

go.mod

@@ -0,0 +1,19 @@
+module github.com/pvainio/scd30-mqtt
+
+go 1.17
+
+require github.com/pvainio/scd30 v0.0.1
+
+require (
+	github.com/gorilla/websocket v1.4.2 // indirect
+	golang.org/x/net v0.0.0-20211029224645-99673261e6eb // indirect
+)
+
+require (
+	github.com/eclipse/paho.mqtt.golang v1.3.5
+	github.com/kelseyhightower/envconfig v1.4.0
+	github.com/sigurn/crc8 v0.0.0-20160107002456-e55481d6f45c // indirect
+	github.com/sigurn/utils v0.0.0-20190728110027-e1fefb11a144 // indirect
+	periph.io/x/conn/v3 v3.6.9
+	periph.io/x/host/v3 v3.7.1
+)

go.sum

@@ -0,0 +1,29 @@
+github.com/eclipse/paho.mqtt.golang v1.3.5 h1:sWtmgNxYM9P2sP+xEItMozsR3w0cqZFlqnNN1bdl41Y=
+github.com/eclipse/paho.mqtt.golang v1.3.5/go.mod h1:eTzb4gxwwyWpqBUHGQZ4ABAV7+Jgm1PklsYT/eo8Hcc=
+github.com/gorilla/websocket v1.4.2 h1:+/TMaTYc4QFitKJxsQ7Yye35DkWvkdLcvGKqM+x0Ufc=
+github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/jonboulle/clockwork v0.2.2 h1:UOGuzwb1PwsrDAObMuhUnj0p5ULPj8V/xJ7Kx9qUBdQ=
+github.com/jonboulle/clockwork v0.2.2/go.mod h1:Pkfl5aHPm1nk2H9h0bjmnJD/BcgbGXUBGnn1kMkgxc8=
+github.com/kelseyhightower/envconfig v1.4.0 h1:Im6hONhd3pLkfDFsbRgu68RDNkGF1r3dvMUtDTo2cv8=
+github.com/kelseyhightower/envconfig v1.4.0/go.mod h1:cccZRl6mQpaq41TPp5QxidR+Sa3axMbJDNb//FQX6Gg=
+github.com/pvainio/scd30 v0.0.0 h1:ISENJRndmH+EeqhYWd9WHXF8ZW558tjV8/YF4qwAn5k=
+github.com/pvainio/scd30 v0.0.0/go.mod h1:wf93naSx0qvVeZUPMepOpcIOw4svGg+3+6SEOdhICIk=
+github.com/pvainio/scd30 v0.0.1 h1:YMmgDn4dwoZe6K6l3ZBUcZBeqJuQXFT5cSERANboDAo=
+github.com/pvainio/scd30 v0.0.1/go.mod h1:wf93naSx0qvVeZUPMepOpcIOw4svGg+3+6SEOdhICIk=
+github.com/sigurn/crc8 v0.0.0-20160107002456-e55481d6f45c h1:hk0Jigjfq59yDMgd6bzi22Das5tyxU0CtOkh7a9io84=
+github.com/sigurn/crc8 v0.0.0-20160107002456-e55481d6f45c/go.mod h1:cyrWuItcOVIGX6fBZ/G00z4ykprWM7hH58fSavNkjRg=
+github.com/sigurn/utils v0.0.0-20190728110027-e1fefb11a144 h1:ccb8W1+mYuZvlpn/mJUMAbsFHTMCpcJBS78AsBQxNcY=
+github.com/sigurn/utils v0.0.0-20190728110027-e1fefb11a144/go.mod h1:VRI4lXkrUH5Cygl6mbG1BRUfMMoT2o8BkrtBDUAm+GU=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/net v0.0.0-20200425230154-ff2c4b7c35a0 h1:Jcxah/M+oLZ/R4/z5RzfPzGbPXnVDPkEDtf2JnuxN+U=
+golang.org/x/net v0.0.0-20200425230154-ff2c4b7c35a0/go.mod h1:qpuaurCH72eLCgpAm/N6yyVIVM9cpaDIP3A8BGJEC5A=
+golang.org/x/net v0.0.0-20211029224645-99673261e6eb h1:pirldcYWx7rx7kE5r+9WsOXPXK0+WH5+uZ7uPmJ44uM=
+golang.org/x/net v0.0.0-20211029224645-99673261e6eb/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20200323222414-85ca7c5b95cd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+periph.io/x/conn/v3 v3.6.9 h1:cSAvXC6IRRYC9pTW/Fzhp0a7zq+aeAxV8+/JZ+oxwZI=
+periph.io/x/conn/v3 v3.6.9/go.mod h1:UqWNaPMosWmNCwtufoTSTTYhB2wXWsMRAJyo1PlxO4Q=
+periph.io/x/d2xx v0.0.4/go.mod h1:38Euaaj+s6l0faIRHh32a+PrjXvxFTFkPBEQI0TKg34=
+periph.io/x/host/v3 v3.7.1 h1:SAe/7IWSOoFsqh2/74+SxbqehzOPny+jAPs25fd/NUI=
+periph.io/x/host/v3 v3.7.1/go.mod h1:kqMB+cJHtIPQCCMqDoiIMwr0pu1p+qQObkrPha3mX6E=

main.go

@@ -0,0 +1,279 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math"
+	"os"
+	"time"
+
+	"github.com/pvainio/scd30"
+
+	"periph.io/x/conn/v3/i2c/i2creg"
+	"periph.io/x/host/v3"
+
+	"github.com/kelseyhightower/envconfig"
+
+	mqttClient "github.com/eclipse/paho.mqtt.golang"
+)
+
+type Config struct {
+	MqttUrl      string `envconfig:"mqtt_url" required:"true"`
+	MqttUser     string `envconfig:"mqtt_user"`
+	MqttPwd      string `envconfig:"mqtt_password"`
+	MqttClientId string `envconfig:"mqtt_client_id" default:"scd30"`
+	Interval     uint16 `envconfig:"interval" default:"50"`
+	TempOffset   uint16 `envconfig:"temp_offset" default:"150"`
+	Id           string `envconfig:"id" default:"scd30"`
+	Name         string `envconfig:"name" default:"SCD30"`
+	Debug        bool   `envconfig:"debug" default:"false"`
+}
+
+type measurement struct {
+	id     string
+	time   time.Time
+	value  float32
+	format string
+	min    float32
+	max    float32
+}
+
+var (
+	config Config
+
+	logInfo  *log.Logger
+	logDebug *log.Logger
+
+	co2         *measurement
+	humidity    *measurement
+	temperature *measurement
+
+	mqtt mqttClient.Client
+
+	homeassistantStatus = make(chan string, 10)
+)
+
+func main() {
+
+	mqtt = connectMqtt()
+
+	dev, err := openSCD30()
+	if err != nil {
+		log.Fatalf("error %v", err)
+	}
+
+	if err := dev.StartMeasurements(config.Interval); err != nil {
+		log.Fatalf("error %v", err)
+	}
+
+	if err := dev.SetAutomaticSelfCalibration(1); err != nil {
+		log.Fatalf("error %v", err)
+	}
+
+	announceMeToMqttDiscovery(mqtt)
+
+	for {
+		select {
+		case <-time.After(time.Duration(config.Interval) * time.Second):
+			checkMeasurement(dev)
+		case status := <-homeassistantStatus:
+			if status == "online" {
+				// HA became online, send discovery so it knows about entities
+				go announceMeToMqttDiscovery(mqtt)
+			} else if status != "offline" {
+				logInfo.Printf("unknown HA status message %s", status)
+			}
+
+		}
+	}
+}
+
+func openSCD30() (*scd30.SCD30, error) {
+	if _, err := host.Init(); err != nil {
+		return nil, err
+	}
+
+	bus, err := i2creg.Open("")
+	if err != nil {
+		return nil, err
+	}
+
+	dev, err := scd30.Open(bus)
+	if err != nil {
+		return nil, err
+	}
+
+	var to uint16 = config.TempOffset
+	if o, err := dev.GetTemperatureOffset(); err != nil {
+		return nil, err
+	} else {
+		logInfo.Printf("Got temp offset %d", o)
+		if o != to {
+			logInfo.Printf("Setting offset to %d", to)
+			if err := dev.SetTemperatureOffset(to); err != nil {
+				return nil, err
+			}
+		}
+	}
+	return dev, nil
+}
+
+func checkMeasurement(dev *scd30.SCD30) {
+	if has, err := dev.HasMeasurement(); err != nil {
+		log.Fatalf("error %v", err)
+	} else if !has {
+		return
+	}
+
+	m, err := dev.GetMeasurement()
+	if err != nil {
+		log.Fatalf("error %v", err)
+	}
+
+	logInfo.Printf("Got measure %f ppm %f%% %fC", m.CO2, m.Humidity, m.Temperature)
+
+	publishIfNeeded(m.CO2, co2, 50)
+	publishIfNeeded(m.Temperature, temperature, 0.3)
+	publishIfNeeded(m.Humidity, humidity, 2)
+}
+
+func publishIfNeeded(current float32, old *measurement, diff float64) {
+	if time.Since(old.time) < 600*time.Second && math.Abs(float64(current)-float64(old.value)) < diff {
+		return
+	}
+
+	if current < old.min || current > old.max {
+		logInfo.Printf("value for %s is out of range %f", old.id, current)
+		return
+	}
+
+	old.time = time.Now()
+	old.value = current
+
+	publish(mqtt, stateTopic(old.id), fmt.Sprintf(old.format, current))
+}
+
+func subscribe(mqtt mqttClient.Client) {
+	logInfo.Print("subscribed to topics")
+	mqtt.Subscribe("homeassistant/status", 0, haStatusHandler)
+}
+
+func haStatusHandler(mqtt mqttClient.Client, msg mqttClient.Message) {
+	body := string(msg.Payload())
+	logInfo.Printf("received HA status %s", body)
+	homeassistantStatus <- body
+}
+
+func announceMeToMqttDiscovery(mqtt mqttClient.Client) {
+	publishDiscovery(mqtt, "co2", "co2", "ppm", "carbon_dioxide")
+	publishDiscovery(mqtt, "temperature", "temperature", "°C", "temperature")
+	publishDiscovery(mqtt, "humidity", "humidity", "%", "humidity")
+}
+
+func publishDiscovery(mqtt mqttClient.Client, id string, name string, unit string, class string) {
+	uid := config.Id + "_" + id
+	pname := config.Name + " " + name
+	discoveryTopic := fmt.Sprintf("homeassistant/sensor/%s/config", uid)
+	msg := discoveryMsg(id, uid, pname, unit, class)
+	publish(mqtt, discoveryTopic, msg)
+}
+
+func publish(mqtt mqttClient.Client, topic string, msg interface{}) {
+
+	logDebug.Printf("publish to %s: %s", topic, msg)
+
+	t := mqtt.Publish(topic, 0, false, msg)
+	go func() {
+		_ = t.Wait()
+		if t.Error() != nil {
+			logInfo.Printf("publishing msg failed %v", t.Error())
+		}
+	}()
+}
+
+func discoveryMsg(id string, uid string, name string, unit string, class string) []byte {
+	msg := make(map[string]interface{})
+	msg["unique_id"] = uid
+	msg["name"] = name
+
+	dev := make(map[string]string)
+	msg["device"] = dev
+	dev["identifiers"] = config.Id
+	dev["manufacturer"] = "Sensirion"
+	dev["name"] = "Sensirion SCD30"
+	dev["model"] = "SCD30"
+
+	msg["state_topic"] = stateTopic(id)
+
+	msg["expire_after"] = 1800
+
+	msg["unit_of_measurement"] = unit
+	msg["state_class"] = "measurement"
+	msg["device_class"] = class
+
+	jsonm, err := json.Marshal(msg)
+	if err != nil {
+		logInfo.Printf("cannot marshal json %v", err)
+	}
+	return jsonm
+}
+
+func stateTopic(id string) string {
+	return "scd30/" + config.Id + "/" + id
+}
+
+func init() {
+
+	co2 = &measurement{id: "co2", format: "%.0f", min: 100, max: 10000}
+	humidity = &measurement{id: "humidity", format: "%.0f", min: 1, max: 100}
+	temperature = &measurement{id: "temperature", format: "%.1f", min: -50, max: 150}
+
+	err := envconfig.Process("scd30", &config)
+	if err != nil {
+		log.Fatal(err.Error())
+	}
+
+	logInfo = log.New(os.Stdout, "INFO  ", log.Ldate|log.Ltime|log.Lmsgprefix)
+
+	if config.Debug {
+		logDebug = log.New(os.Stdout, "DEBUG ", log.Ldate|log.Ltime|log.Lmsgprefix)
+	} else {
+		logDebug = log.New(ioutil.Discard, "DEBUG ", 0)
+	}
+}
+
+func connectHandler(client mqttClient.Client) {
+	options := client.OptionsReader()
+	logInfo.Printf("MQTT connected to %s", options.Servers())
+	subscribe(client)
+}
+
+func connectMqtt() mqttClient.Client {
+
+	opts := mqttClient.NewClientOptions().
+		AddBroker(config.MqttUrl).
+		SetClientID(config.MqttClientId).
+		SetOrderMatters(false).
+		SetKeepAlive(150 * time.Second).
+		SetAutoReconnect(true).
+		SetOnConnectHandler(connectHandler)
+
+	if len(config.MqttUser) > 0 {
+		opts = opts.SetUsername(config.MqttUser)
+	}
+
+	if len(config.MqttPwd) > 0 {
+		opts = opts.SetPassword(config.MqttPwd)
+	}
+
+	logInfo.Printf("connecting to mqtt %s client id %s user %s", opts.Servers, opts.ClientID, opts.Username)
+
+	c := mqttClient.NewClient(opts)
+	if token := c.Connect(); token.Wait() && token.Error() != nil {
+		panic(token.Error())
+	}
+
+	return c
+}