Initial commit

README.md

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+# Sensirion SCD30 CO2 sensor i2c driver module for Golang
+
+## Overview
+
+With this module Sensirion SCD30 CO2 sensor can be accessed throug i2c bus.
+Implemented:
+- starting and stopping continuous measurements
+- checking for ready measurement
+- reading ready measurement
+- getting and setting temperature compensation
+
+## Example
+
+```go
+package main
+
+import (
+	"log"
+	"time"
+
+	"github.com/pvainio/scd30"
+	"periph.io/x/conn/v3/i2c/i2creg"
+	"periph.io/x/host/v3"
+)
+
+func main() {
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	bus, err := i2creg.Open("")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer bus.Close()
+
+	dev, err := scd30.Open(bus)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var interval uint16 = 5
+
+	dev.StartMeasurements(interval)
+
+	for {
+		time.Sleep(time.Duration(interval) * time.Second)
+		if hasMeasurement, err := dev.HasMeasurement(); err != nil {
+			log.Fatalf("error %v", err)
+		} else if !hasMeasurement {
+			return
+		}
+
+		m, err := dev.GetMeasurement()
+		if err != nil {
+			log.Fatalf("error %v", err)
+		}
+
+		log.Printf("Got measure %f ppm %f%% %fC", m.CO2, m.Humidity, m.Temperature)
+	}
+}
+```

example_test.go

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+package scd30_test
+
+import (
+	"log"
+	"time"
+
+	"github.com/pvainio/scd30"
+	"periph.io/x/conn/v3/i2c/i2creg"
+	"periph.io/x/host/v3"
+)
+
+func Example() {
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	bus, err := i2creg.Open("")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer bus.Close()
+
+	dev, err := scd30.Open(bus)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	var interval uint16 = 5
+
+	dev.StartMeasurements(interval)
+
+	for {
+		time.Sleep(time.Duration(interval) * time.Second)
+		if hasMeasurement, err := dev.HasMeasurement(); err != nil {
+			log.Fatalf("error %v", err)
+		} else if !hasMeasurement {
+			return
+		}
+
+		m, err := dev.GetMeasurement()
+		if err != nil {
+			log.Fatalf("error %v", err)
+		}
+
+		log.Printf("Got measure %f ppm %f%% %fC", m.CO2, m.Humidity, m.Temperature)
+	}
+}

go.mod

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+module github.com/pvainio/scd30
+
+go 1.17
+
+require (
+	github.com/sigurn/crc8 v0.0.0-20160107002456-e55481d6f45c
+	periph.io/x/conn/v3 v3.6.9
+	periph.io/x/host/v3 v3.7.1
+)
+
+require github.com/sigurn/utils v0.0.0-20190728110027-e1fefb11a144 // indirect

go.sum

@@ -0,0 +1,11 @@
+github.com/jonboulle/clockwork v0.2.2 h1:UOGuzwb1PwsrDAObMuhUnj0p5ULPj8V/xJ7Kx9qUBdQ=
+github.com/jonboulle/clockwork v0.2.2/go.mod h1:Pkfl5aHPm1nk2H9h0bjmnJD/BcgbGXUBGnn1kMkgxc8=
+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=
+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=

scd30.go

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+package scd30
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"math"
+	"sync"
+	"time"
+
+	"periph.io/x/conn/v3/i2c"
+
+	"github.com/sigurn/crc8"
+)
+
+type Measurement struct {
+	CO2         float32
+	Temperature float32
+	Humidity    float32
+}
+
+type SCD30 struct {
+	dev *i2c.Dev
+}
+
+var mutex sync.Mutex
+
+func Open(bus i2c.Bus) (*SCD30, error) {
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	dev := &i2c.Dev{Addr: 0x61, Bus: bus}
+
+	return &SCD30{dev: dev}, nil
+}
+
+// StartMeasurements starts continous measerements at given interval seconds
+func (dev SCD30) StartMeasurements(interval uint16) error {
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	// Set measurement interval
+	if err := dev.sendCommandArg(0x4600, interval); err != nil {
+		return err
+	}
+
+	// Start continuous measurements
+	if err := dev.sendCommandArg(0x0010, 0); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// StopMeasurements stops continuous measurements
+func (dev SCD30) StopMeasurements() error {
+	mutex.Lock()
+	defer mutex.Unlock()
+	return dev.sendCommand(0x0104)
+}
+
+// GetTemperatureOffset gets temperature offset to compensate internal
+// heating.  Value is 1/100C
+func (dev SCD30) GetTemperatureOffset() (uint16, error) {
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	if err := dev.sendCommand(0x5403); err != nil {
+		return 0, err
+	}
+
+	data, err := dev.readData(3)
+
+	if err != nil {
+		return 0, err
+	}
+	data, err = readValid16(bytes.NewBuffer(data))
+	if err != nil {
+		return 0, err
+	} else {
+		return binary.BigEndian.Uint16(data), nil
+	}
+}
+
+// SetTemperatureOffset sets temperature offset to compensate internal
+// heating.  Value is 1/100C
+func (dev SCD30) SetTemperatureOffset(offset uint16) error {
+	mutex.Lock()
+	defer mutex.Unlock()
+	return dev.sendCommandArg(0x5403, offset)
+}
+
+// GetMeasurement returns ready measurement.  HasMeasurement should be
+// used first to check if there is one.
+func (dev SCD30) GetMeasurement() (*Measurement, error) {
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	if err := dev.sendCommand(0x0300); err != nil {
+		return nil, err
+	}
+
+	if data, err := dev.readData(18); err != nil {
+		return nil, err
+	} else {
+		buf := bytes.NewBuffer(data)
+		co2, err := readValidFloat32(buf)
+		if err != nil {
+			return nil, err
+		}
+		temp, err := readValidFloat32(buf)
+		if err != nil {
+			return nil, err
+		}
+		hum, err := readValidFloat32(buf)
+		if err != nil {
+			return nil, err
+		}
+		return &Measurement{CO2: co2, Temperature: temp, Humidity: hum}, nil
+	}
+}
+
+// HasMeasurement checks if there is ready measurement
+func (dev SCD30) HasMeasurement() (bool, error) {
+	mutex.Lock()
+	defer mutex.Unlock()
+
+	if err := dev.sendCommand(0x0202); err != nil {
+		return false, err
+	}
+
+	if data, err := dev.readData(3); err != nil {
+		return false, err
+	} else {
+		if data[2] != crc(data[:2]) {
+			return false, fmt.Errorf("crc error, expected %x got %x", crc(data[:2]), data[2])
+		}
+		return data[1] == 1, nil
+	}
+}
+
+func (dev SCD30) readData(len int) ([]byte, error) {
+
+	data := make([]byte, len)
+
+	if err := dev.dev.Tx(nil, data); err != nil {
+		return nil, err
+	} else {
+		return data, nil
+	}
+}
+
+func (dev SCD30) sendCommand(cmd uint16) error {
+	cmdData := make([]byte, 2)
+	binary.BigEndian.PutUint16(cmdData, cmd)
+	return dev.writeAndWait(cmdData)
+}
+
+func (dev SCD30) sendCommandArg(cmd uint16, arg uint16) error {
+	cmdData := make([]byte, 2)
+	argData := make([]byte, 2)
+	binary.BigEndian.PutUint16(cmdData, cmd)
+	binary.BigEndian.PutUint16(argData, arg)
+	write := []byte{cmdData[0], cmdData[1], argData[0], argData[1], crc(argData)}
+	return dev.writeAndWait(write)
+}
+
+func (dev SCD30) writeAndWait(data []byte) error {
+
+	if err := dev.dev.Tx(data, nil); err != nil {
+		return err
+	}
+
+	time.Sleep(4 * time.Millisecond)
+
+	return nil
+}
+
+func crc(data []byte) byte {
+	return crc8.Checksum(data, crcTable)
+}
+
+func readValid16(buf *bytes.Buffer) ([]byte, error) {
+	data := buf.Next(2)
+	crc8, err := buf.ReadByte()
+	if err != nil {
+		return nil, err
+	}
+	if crc(data) != crc8 {
+		return nil, fmt.Errorf("crc error, expected %x got %x", crc(data), crc8)
+	}
+	return data, nil
+}
+
+func readValidFloat32(buf *bytes.Buffer) (float32, error) {
+	var out bytes.Buffer
+
+	for i := 0; i < 2; i++ {
+		if data, err := readValid16(buf); err != nil {
+			return float32(math.NaN()), err
+		} else {
+			out.Write(data)
+		}
+	}
+	uint := binary.BigEndian.Uint32(out.Bytes())
+	return math.Float32frombits(uint), nil
+}
+
+var crcTable *crc8.Table
+
+func init() {
+	crcTable = crc8.MakeTable(crc8.Params{Poly: 0x31, Init: 0xff, RefIn: false, RefOut: false, XorOut: 0x00, Check: 0xff, Name: "Sensirion"})
+}