diff --git a/samples/hcsr501.go b/samples/hcsr501.go
new file mode 100644
index 0000000..89e0d00
--- /dev/null
+++ b/samples/hcsr501.go
@@ -0,0 +1,41 @@
+// +build ignore
+
+package main
+
+import (
+	"flag"
+	"log"
+	"time"
+
+	"github.com/kidoman/embd"
+
+	_ "github.com/kidoman/embd/host/chip"
+	"github.com/kidoman/embd/sensor/hcsr501"
+)
+
+func main() {
+	flag.Parse()
+
+	if err := embd.InitGPIO(); err != nil {
+		panic(err)
+	}
+	defer embd.CloseGPIO()
+
+	trig, err := embd.NewDigitalPin(132)
+	if err != nil {
+		panic(err)
+	}
+	defer trig.Close()
+
+	pir := hcsr501.New(trig)
+
+	for {
+		time.Sleep(3 * time.Second)
+		p, err := pir.Detect()
+		if err != nil {
+			log.Printf("error %v", err)
+			continue
+		}
+		log.Printf("PIR Detect %v", p)
+	}
+}
diff --git a/sensor/hcsr501/hcsr501.go b/sensor/hcsr501/hcsr501.go
new file mode 100644
index 0000000..4da90ac
--- /dev/null
+++ b/sensor/hcsr501/hcsr501.go
@@ -0,0 +1,77 @@
+// Package hcsr501 allows interfacing with the HC-SR501 PIR Sensor.
+package hcsr501
+
+import (
+	"errors"
+	"sync"
+	"time"
+
+	"github.com/kidoman/embd"
+)
+
+// HCSR501 represents a HCSR501 ultrasonic range finder.
+type HCSR501 struct {
+	TriggerPin  embd.DigitalPin
+	initialized bool
+	ready       bool // Allows the sensor time to settle in.
+	mu          sync.RWMutex
+}
+
+// New creates a new HCSR501 interface.
+func New(triggerPin embd.DigitalPin) *HCSR501 {
+	return &HCSR501{TriggerPin: triggerPin}
+}
+
+// setup initializes the GPIO and sensor.
+func (d *HCSR501) setup() error {
+	d.mu.RLock()
+	if d.initialized {
+		d.mu.RUnlock()
+		return nil
+	}
+	d.mu.RUnlock()
+
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if err := d.TriggerPin.SetDirection(embd.In); err != nil {
+		return err
+	}
+
+	// Wait 60 sec for sensor to settle down.
+	time.AfterFunc(60*time.Second, func() {
+		d.ready = true
+	})
+	d.initialized = true
+
+	return nil
+}
+
+// Detect returns true if motion was detected.
+func (d *HCSR501) Detect() (bool, error) {
+	if err := d.setup(); err != nil {
+		return false, err
+	}
+
+	if !d.ready {
+		return false, errors.New("Sensor not ready")
+	}
+
+	// Check 3 times to be sure.
+	for i := 0; i < 3; i++ {
+		v, err := d.TriggerPin.Read()
+		if err != nil {
+			return false, err
+		}
+		if v == embd.Low {
+			return false, nil
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	return true, nil
+}
+
+// Close.
+func (d *HCSR501) Close() error {
+	return d.TriggerPin.SetDirection(embd.Out)
+}