devices/ds18b20: issue 59 add demo

ds18b20/main.go

@@ -0,0 +1,112 @@
+// Copyright 2024 The Periph Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+//
+// This program enumerates onewire buses for  DS18B20 sensors and
+// continuously reading them.
+//
+// If you get the error no buses were found, ensure that onewire buses
+// are enabled. On a Raspberry Pi, run raspi-config, Interface Options,
+// and enable 1-Wire. Remember to reboot after enabling it.
+package main
+
+import (
+	"fmt"
+	"log"
+	"time"
+
+	"periph.io/x/conn/v3/onewire"
+	"periph.io/x/conn/v3/onewire/onewirereg"
+	"periph.io/x/devices/v3/ds18b20"
+	"periph.io/x/host/v3"
+)
+
+// For the Dallas onewire devices, the conversion time is dependent on the
+// resolution. Refer to the Datasheet for more information.
+const DefaultBits = 10
+
+// enumerateBusForSensors searches for addresses on the bus and if it finds
+// a DS18X20 series device, returns it.
+func enumerateBusForSensors(bus onewire.Bus) []*ds18b20.Dev {
+	result := make([]*ds18b20.Dev, 0)
+	addresses, err := bus.Search(false)
+	if err != nil {
+		log.Print("  Search error:", err)
+		return result
+	}
+
+	for _, address := range addresses {
+		family := ds18b20.Family(address & 0xff)
+		if family == ds18b20.DS18S20 || family == ds18b20.DS18B20 {
+			log.Printf("Found Device %s Address %#016X\n", family, address)
+			dev, err := ds18b20.New(bus, address, DefaultBits)
+			if err != nil {
+				log.Print(err)
+			} else {
+				result = append(result, dev)
+			}
+		}
+	}
+	return result
+}
+
+func main() {
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	buses := make([]onewire.Bus, 0)
+	sensors := make([]*ds18b20.Dev, 0)
+	for _, ref := range onewirereg.All() {
+		log.Printf("Found One-Wire Bus %s\n", ref.Name)
+		busCloser, err := ref.Open()
+		if err != nil {
+			fmt.Println(" Open error:", err)
+			continue
+		}
+		bus := busCloser.(onewire.Bus)
+		newSensors := enumerateBusForSensors(bus)
+		if len(newSensors) > 0 {
+			// Do an initial convert on all devices on the bus.
+			err = ds18b20.ConvertAll(bus, DefaultBits)
+			if err != nil {
+				log.Println(err)
+			}
+			buses = append(buses, bus)
+			sensors = append(sensors, newSensors...)
+		}
+	}
+	if len(buses) == 0 {
+		log.Fatal("no onewire buses found.")
+	}
+	if len(sensors) == 0 {
+		log.Fatal("no DS18X20 sensors found.")
+	}
+
+	// This demo uses StartAll()/LastTemp() to read without any latency.
+	// You can also use Sense() to read the units, but there will be
+	// the conversion latency.
+	for {
+		out := fmt.Sprintf("%d ", time.Now().Unix())
+		for _, dev := range sensors {
+			t, err := dev.LastTemp()
+			if err == nil {
+				out += fmt.Sprintf("%.2f ", t.Celsius())
+			} else {
+				log.Print(err)
+				out += "err "
+			}
+
+		}
+		fmt.Println(out)
+
+		for _, bus := range buses {
+			// Start the conversion cycle running while we're sleeping ...
+			err := ds18b20.StartAll(bus)
+			if err != nil {
+				log.Println(err)
+			}
+		}
+		time.Sleep(time.Duration(1000-(time.Now().UnixMilli()%1000)) * time.Millisecond)
+	}
+}