first implementation of 1-wire protocol (#505)

onewire: initial implementation for protocol and ds18b20 device

examples/ds18b20/main.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"encoding/hex"
+	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/onewire"
+
+	"tinygo.org/x/drivers/ds18b20"
+)
+
+func main() {
+	// Define pin for DS18B20
+	pin := machine.D2
+
+	ow := onewire.New(pin)
+	romIDs, err := ow.Search(onewire.SEARCH_ROM)
+	if err != nil {
+		println(err)
+	}
+	sensor := ds18b20.New(ow)
+
+	for {
+		time.Sleep(3 * time.Second)
+
+		println()
+		println("Device:", machine.Device)
+
+		println()
+		println("Request Temperature.")
+		for _, romid := range romIDs {
+			println("Sensor RomID: ", hex.EncodeToString(romid))
+			sensor.RequestTemperature(romid)
+		}
+
+		// wait 750ms or more for DS18B20 convert T
+		time.Sleep(1 * time.Second)
+
+		println()
+		println("Read Temperature")
+		for _, romid := range romIDs {
+			raw, err := sensor.ReadTemperatureRaw(romid)
+			if err != nil {
+				println(err)
+			}
+			println()
+			println("Sensor RomID: ", hex.EncodeToString(romid))
+			println("Temperature Raw value: ", hex.EncodeToString(raw))
+
+			t, err := sensor.ReadTemperature(romid)
+			if err != nil {
+				println(err)
+			}
+			println("Temperature in celsius milli degrees (°C/1000): ", t)
+		}
+	}
+}

examples/onewire/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"encoding/hex"
+	"time"
+	"tinygo.org/x/drivers/onewire"
+)
+
+func main() {
+
+	pin := machine.D2
+
+	ow := onewire.New(pin)
+
+	for {
+		time.Sleep(3 * time.Second)
+
+		println()
+		println("Device:", machine.Device)
+
+		romIDs, err := ow.Search(onewire.SEARCH)
+		if err != nil {
+			println(err)
+		}
+		for _, romid := range romIDs {
+			println(hex.EncodeToString(romid))
+		}
+
+		if len(romIDs) == 1 {
+			// only 1 device on bus
+			r, err := ow.ReadAddress()
+			if err != nil {
+				println(err)
+			}
+			println(hex.EncodeToString(r))
+
+		}
+
+	}
+}