ds18b20 - requires https://github.com/kidoman/embd/pull/54

samples/ds18b20.go

@@ -0,0 +1,78 @@
+// +build ignore
+
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/zlowred/embd"
+	"github.com/zlowred/embd/sensor/ds18b20"
+	_ "github.com/zlowred/embd/host/rpi"
+)
+
+func main() {
+	if err := embd.InitW1(); err != nil {
+		panic(err)
+	}
+	defer embd.CloseW1()
+
+	w1 := embd.NewW1Bus(0)
+
+	devs, err := w1.ListDevices()
+
+	if err != nil {
+		panic(err)
+	}
+
+	var name string = ""
+	for _, dev := range devs {
+		if strings.HasPrefix(dev, "28-") {
+			name = dev
+			break
+		}
+	}
+
+	if name == "" {
+		fmt.Println("No DS18B20 devices found")
+	}
+
+	fmt.Printf("Using DS18B20 device %s\n", name)
+	w1d, err := w1.Open(name)
+
+	if err != nil {
+		panic(err)
+	}
+
+	sensor := ds18b20.New(w1d)
+
+	err = sensor.SetResolution(ds18b20.Resolution_12bit)
+
+	if err != nil {
+		panic(err)
+	}
+
+	err = sensor.ReadTemperature()
+
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("Measured temperature: %vC\n", sensor.Celsius())
+	fmt.Printf("Measured temperature: %vF\n", sensor.Fahrenheit())
+
+	err = sensor.SetResolution(ds18b20.Resolution_9bit)
+
+	if err != nil {
+		panic(err)
+	}
+
+	err = sensor.ReadTemperature()
+
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("Measured temperature: %vC\n", sensor.Celsius())
+	fmt.Printf("Measured temperature: %vF\n", sensor.Fahrenheit())
+}

sensor/ds18b20/ds18b20.go

@@ -0,0 +1,146 @@
+// Support for the very popular DS18B20 1-WIre temperature sensor
+package ds18b20
+import (
+	"github.com/zlowred/embd"
+	"errors"
+	"sync"
+)
+
+type DS18B20_Resolution int
+
+const (
+	Resolution_9bit DS18B20_Resolution = iota
+	Resolution_10bit
+	Resolution_11bit
+	Resolution_12bit
+)
+
+var ds18b20_crc_data = [...]byte{
+	0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65,
+	157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220,
+	35, 125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98,
+	190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255,
+	70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7,
+	219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154,
+	101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36,
+	248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185,
+	140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205,
+	17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80,
+	175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238,
+	50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115,
+	202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139,
+	87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22,
+	233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168,
+	116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53,
+}
+// DS18B20 represents a DS18B20 temperature sensor.
+type DS18B20 struct {
+	Device embd.W1Device
+
+	Raw    int16
+	mu     sync.Mutex
+}
+
+// New returns a handle to a DS18B20 sensor.
+func New(device embd.W1Device) *DS18B20 {
+	return &DS18B20{Device: device}
+}
+
+func ds18b20_crc(data []byte) byte {
+	var crc byte = 0
+	var x byte
+	for _, x := range data {
+		crc = ds18b20_crc_data[crc ^ x]
+	}
+	return x
+}
+
+func (sensor *DS18B20) ReadTemperature() error {
+	sensor.mu.Lock()
+	defer sensor.mu.Unlock()
+
+	err := sensor.Device.WriteByte(0x44)
+
+	if err != nil {
+		return err
+	}
+
+	for ret, err := sensor.Device.ReadByte(); ret == 0 && err != nil; {}
+
+	if err != nil {
+		return err
+	}
+
+	err = sensor.Device.WriteByte(0xBE)
+
+	if err != nil {
+		return err
+	}
+
+	res, err := sensor.Device.ReadBytes(9)
+
+	if err != nil {
+		return err
+	}
+
+	crc := ds18b20_crc(res[:8])
+
+	if crc != res[8] {
+		errors.New("CRC error")
+	}
+
+	sensor.Raw = int16(res[1]) * 256 + int16(res[0])
+	cfg := res[4] & 0x60
+
+	switch cfg {
+	case 0x00:
+		sensor.Raw &^= 7
+	case 0x20:
+		sensor.Raw &^= 3
+	case 0x40:
+		sensor.Raw &^= 1
+	}
+
+	return nil
+}
+
+func (sensor *DS18B20) Celsius() float32 {
+	return float32(sensor.Raw) * 0.0625
+}
+
+func (sensor *DS18B20) Fahrenheit() float32 {
+	return float32(sensor.Raw) * 0.1125 + 32.
+}
+
+func (sensor *DS18B20) SetResolution(resoultion DS18B20_Resolution) error {
+	sensor.mu.Lock()
+	defer sensor.mu.Unlock()
+
+	err := sensor.Device.WriteByte(0x4E)
+	if err != nil {
+		return err
+	}
+	err = sensor.Device.WriteByte(0x00)
+	if err != nil {
+		return err
+	}
+	err = sensor.Device.WriteByte(0x00)
+	if err != nil {
+		return err
+	}
+	switch resoultion {
+	case Resolution_9bit:
+		err = sensor.Device.WriteByte(0x1F)
+	case Resolution_10bit:
+		err = sensor.Device.WriteByte(0x3F)
+	case Resolution_11bit:
+		err = sensor.Device.WriteByte(0x5F)
+	case Resolution_12bit:
+		err = sensor.Device.WriteByte(0x7F)
+	}
+	if err != nil {
+		return err
+	}
+	return nil
+}
+