Add AHT20 example code (#71)

* add AHT20 example code

* add Precision() test

aht20/aht20_test.go

@@ -174,3 +174,17 @@ func TestDev_SoftReset(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestDev_Precision(t *testing.T) {
+	dev := Dev{d: &i2c.Dev{Bus: &i2ctest.Playback{}, Addr: deviceAddress}, opts: DefaultOpts}
+	var env physic.Env
+	dev.Precision(&env)
+
+	if env.Temperature == 0 {
+		t.Fatal("expected temperature precision")
+	} else if env.Pressure != 0 {
+		t.Fatal("expected no pressure precision")
+	} else if env.Humidity == 0 {
+		t.Fatal("expected humidity precision")
+	}
+}

aht20/example_test.go

@@ -0,0 +1,41 @@
+// 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.
+
+package aht20_test
+
+import (
+	"fmt"
+	"log"
+	"periph.io/x/conn/v3/i2c/i2creg"
+	"periph.io/x/conn/v3/physic"
+	"periph.io/x/devices/v3/aht20"
+	"periph.io/x/host/v3"
+)
+
+func Example() {
+	// Make sure periph is initialized.
+	if _, err := host.Init(); err != nil {
+		log.Fatal(err)
+	}
+
+	// Use i2creg I²C bus registry to find the first available I²C bus.
+	b, err := i2creg.Open("")
+	if err != nil {
+		log.Fatalf("failed to open I²C: %v", err)
+	}
+	defer b.Close()
+
+	// Create a new AHT20 device using I²C bus.
+	d, err := aht20.NewI2C(b, nil) // nil for default options or &aht20.DefaultOpts
+	if err != nil {
+		log.Fatalf("failed to initialize AHT20: %v", err)
+	}
+
+	// Read temperature and humidity from the sensor
+	e := physic.Env{}
+	if err := d.Sense(&e); err != nil {
+		log.Fatal(err)
+	}
+	fmt.Printf("%8s %9s\n", e.Temperature, e.Humidity)
+}