gpio(hcsr04): add driver for ultrasonic ranging module (#1012)

README.md

@@ -270,7 +270,7 @@ Support for many devices that use General Purpose Input/Output (GPIO) have
 a shared set of drivers provided using the `gobot/drivers/gpio` package:
 
 - [GPIO](https://en.wikipedia.org/wiki/General_Purpose_Input/Output) <=> [Drivers](https://github.com/hybridgroup/gobot/tree/master/drivers/gpio)
-  - AIP1640 LED
+  - AIP1640 LED Dot Matrix/7 Segment Controller
   - Button
   - Buzzer
   - Direct Pin
@@ -281,8 +281,11 @@ a shared set of drivers provided using the `gobot/drivers/gpio` package:
   - Grove Magnetic Switch
   - Grove Relay
   - Grove Touch Sensor
+  - HC-SR04 Ultrasonic Ranging Module
+  - HD44780 LCD controller
   - LED
   - Makey Button
+  - MAX7219 LED Dot Matrix
   - Motor
   - Proximity Infra Red (PIR) Motion Sensor
   - Relay

appveyor.yml

@@ -15,10 +15,9 @@ before_test:
 build_script:
   - go test -v -cpu=2 .
   - go test -v -cpu=2 ./drivers/aio/...
-  - go test -v -cpu=2 ./drivers/i2c/...
+  - go test -v -cpu=2 ./platforms/ble/...
   - go test -v -cpu=2 ./platforms/dji/...
   - go test -v -cpu=2 ./platforms/firmata/...
-  - go test -v -cpu=2 ./platforms/ble/...
   - go test -v -cpu=2 ./platforms/joystick/...
   - go test -v -cpu=2 ./platforms/parrot/...
   - go test -v -cpu=2 ./platforms/sphero/...

drivers/gpio/README.md

@@ -12,17 +12,22 @@ Please refer to the main [README.md](https://github.com/hybridgroup/gobot/blob/r
 
 Gobot has a extensible system for connecting to hardware devices. The following GPIO devices are currently supported:
 
+- AIP1640 LED Dot Matrix/7 Segment Controller
 - Button
 - Buzzer
 - Direct Pin
+- EasyDriver
 - Grove Button
 - Grove Buzzer
 - Grove LED
 - Grove Magnetic Switch
 - Grove Relay
 - Grove Touch Sensor
+- HC-SR04 Ultrasonic Ranging Module
+- HD44780 LCD controller
 - LED
 - Makey Button
+- MAX7219 LED Dot Matrix
 - Motor
 - Proximity Infra Red (PIR) Motion Sensor
 - Relay
@@ -30,5 +35,3 @@ Gobot has a extensible system for connecting to hardware devices. The following
 - Servo
 - Stepper Motor
 - TM1638 LED Controller
-
-More drivers are coming soon...

drivers/gpio/gpio_driver.go

@@ -2,6 +2,9 @@ package gpio
 
 import (
 	"errors"
+	"sync"
+
+	"gobot.io/x/gobot/v2"
 )
 
 var (
@@ -61,3 +64,62 @@ type DigitalWriter interface {
 type DigitalReader interface {
 	DigitalRead(string) (val int, err error)
 }
+
+// Driver implements the interface gobot.Driver.
+type Driver struct {
+	name       string
+	connection gobot.Adaptor
+	afterStart func() error
+	beforeHalt func() error
+	gobot.Commander
+	mutex *sync.Mutex // mutex often needed to ensure that write-read sequences are not interrupted
+}
+
+// NewDriver creates a new generic and basic gpio gobot driver.
+func NewDriver(a gobot.Adaptor, name string) *Driver {
+	d := &Driver{
+		name:       gobot.DefaultName(name),
+		connection: a,
+		afterStart: func() error { return nil },
+		beforeHalt: func() error { return nil },
+		Commander:  gobot.NewCommander(),
+		mutex:      &sync.Mutex{},
+	}
+
+	return d
+}
+
+// Name returns the name of the gpio device.
+func (d *Driver) Name() string {
+	return d.name
+}
+
+// SetName sets the name of the gpio device.
+func (d *Driver) SetName(name string) {
+	d.name = name
+}
+
+// Connection returns the connection of the gpio device.
+func (d *Driver) Connection() gobot.Connection {
+	return d.connection.(gobot.Connection)
+}
+
+// Start initializes the gpio device.
+func (d *Driver) Start() error {
+	d.mutex.Lock()
+	defer d.mutex.Unlock()
+
+	// currently there is nothing to do here for the driver
+
+	return d.afterStart()
+}
+
+// Halt halts the gpio device.
+func (d *Driver) Halt() error {
+	d.mutex.Lock()
+	defer d.mutex.Unlock()
+
+	// currently there is nothing to do after halt for the driver
+
+	return d.beforeHalt()
+}

drivers/gpio/gpio_driver_test.go

@@ -0,0 +1,78 @@
+package gpio
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"gobot.io/x/gobot/v2"
+)
+
+var _ gobot.Driver = (*Driver)(nil)
+
+func initTestDriverWithStubbedAdaptor() (*Driver, *gpioTestAdaptor) {
+	a := newGpioTestAdaptor()
+	d := NewDriver(a, "GPIO_BASIC")
+	return d, a
+}
+
+func initTestDriver() *Driver {
+	d, _ := initTestDriverWithStubbedAdaptor()
+	return d
+}
+
+func TestNewDriver(t *testing.T) {
+	// arrange
+	a := newGpioTestAdaptor()
+	// act
+	var di interface{} = NewDriver(a, "GPIO_BASIC")
+	// assert
+	d, ok := di.(*Driver)
+	if !ok {
+		t.Errorf("NewDriver() should have returned a *Driver")
+	}
+	assert.Contains(t, d.name, "GPIO_BASIC")
+	assert.Equal(t, a, d.connection)
+	assert.NoError(t, d.afterStart())
+	assert.NoError(t, d.beforeHalt())
+	assert.NotNil(t, d.Commander)
+	assert.NotNil(t, d.mutex)
+}
+
+func TestSetName(t *testing.T) {
+	// arrange
+	d := initTestDriver()
+	// act
+	d.SetName("TESTME")
+	// assert
+	assert.Equal(t, "TESTME", d.Name())
+}
+
+func TestConnection(t *testing.T) {
+	// arrange
+	d, a := initTestDriverWithStubbedAdaptor()
+	// act, assert
+	assert.Equal(t, a, d.Connection())
+}
+
+func TestStart(t *testing.T) {
+	// arrange
+	d := initTestDriver()
+	// act, assert
+	assert.NoError(t, d.Start())
+	// arrange after start function
+	d.afterStart = func() error { return fmt.Errorf("after start error") }
+	// act, assert
+	assert.ErrorContains(t, d.Start(), "after start error")
+}
+
+func TestHalt(t *testing.T) {
+	// arrange
+	d := initTestDriver()
+	// act, assert
+	assert.NoError(t, d.Halt())
+	// arrange after start function
+	d.beforeHalt = func() error { return fmt.Errorf("before halt error") }
+	// act, assert
+	assert.ErrorContains(t, d.Halt(), "before halt error")
+}

drivers/gpio/hcsr04_driver.go

@@ -0,0 +1,218 @@
+package gpio
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"gobot.io/x/gobot/v2"
+	"gobot.io/x/gobot/v2/system"
+)
+
+const (
+	hcsr04SoundSpeed = 343 // in [m/s]
+	// the device can measure 2 cm .. 4 m, this means sweep distances between 4 cm and 8 m
+	// this cause pulse duration between 0.12 ms and 24 ms (at 34.3 cm/ms, ~0.03 ms/cm, ~3 ms/m)
+	// so we use 60 ms as a limit for timeout and 100 ms for duration between 2 consecutive measurements
+	hcsr04StartTransmitTimeout time.Duration = 100 * time.Millisecond // unfortunately takes sometimes longer than 60 ms
+	hcsr04ReceiveTimeout       time.Duration = 60 * time.Millisecond
+	hcsr04EmitTriggerDuration  time.Duration = 10 * time.Microsecond // according to specification
+	hcsr04MonitorUpdate        time.Duration = 200 * time.Millisecond
+	// the resolution of the device is ~3 mm, which relates to 10 us (343 mm/ms = 0.343 mm/us)
+	// the poll interval increases the reading interval to this value and adds around 3 mm inaccuracy
+	// it takes only an effect for fast systems, because reading inputs is typically much slower, e.g. 30-50 us on raspi
+	// so, using the internal edge detection with "cdev" is more precise
+	hcsr04PollInputIntervall time.Duration = 10 * time.Microsecond
+)
+
+// HCSR04Driver is a driver for ultrasonic range measurement.
+type HCSR04Driver struct {
+	*Driver
+	triggerPinID                 string
+	echoPinID                    string
+	useEdgePolling               bool        // use discrete edge polling instead "cdev" from gpiod
+	measureMutex                 *sync.Mutex // to ensure that only one measurement is done at a time
+	triggerPin                   gobot.DigitalPinner
+	echoPin                      gobot.DigitalPinner
+	lastMeasureMicroSec          int64 // ~120 .. 24000 us
+	distanceMonitorStopChan      chan struct{}
+	distanceMonitorStopWaitGroup *sync.WaitGroup
+	delayMicroSecChan            chan int64    // channel for event handler return value
+	pollQuitChan                 chan struct{} // channel for quit the continuous polling
+}
+
+// NewHCSR04Driver creates a new instance of the driver for HC-SR04 (same as SEN-US01).
+//
+// Datasheet: https://www.makershop.de/download/HCSR04-datasheet-version-1.pdf
+func NewHCSR04Driver(a gobot.Adaptor, triggerPinID string, echoPinID string, useEdgePolling bool) *HCSR04Driver {
+	h := HCSR04Driver{
+		Driver:         NewDriver(a, "HCSR04"),
+		triggerPinID:   triggerPinID,
+		echoPinID:      echoPinID,
+		useEdgePolling: useEdgePolling,
+		measureMutex:   &sync.Mutex{},
+	}
+
+	h.afterStart = func() error {
+		tpin, err := a.(gobot.DigitalPinnerProvider).DigitalPin(triggerPinID)
+		if err != nil {
+			return fmt.Errorf("error on get trigger pin: %v", err)
+		}
+		if err := tpin.ApplyOptions(system.WithPinDirectionOutput(0)); err != nil {
+			return fmt.Errorf("error on apply output for trigger pin: %v", err)
+		}
+		h.triggerPin = tpin
+
+		// pins are inputs by default
+		epin, err := a.(gobot.DigitalPinnerProvider).DigitalPin(echoPinID)
+		if err != nil {
+			return fmt.Errorf("error on get echo pin: %v", err)
+		}
+
+		epinOptions := []func(gobot.DigitalPinOptioner) bool{system.WithPinEventOnBothEdges(h.createEventHandler())}
+		if h.useEdgePolling {
+			h.pollQuitChan = make(chan struct{})
+			epinOptions = append(epinOptions, system.WithPinPollForEdgeDetection(hcsr04PollInputIntervall, h.pollQuitChan))
+		}
+		if err := epin.ApplyOptions(epinOptions...); err != nil {
+			return fmt.Errorf("error on apply options for echo pin: %v", err)
+		}
+		h.echoPin = epin
+
+		h.delayMicroSecChan = make(chan int64)
+
+		return nil
+	}
+
+	h.beforeHalt = func() error {
+		if useEdgePolling {
+			close(h.pollQuitChan)
+		}
+
+		if err := h.stopDistanceMonitor(); err != nil {
+			fmt.Printf("no need to stop distance monitoring: %v\n", err)
+		}
+
+		// note: Unexport() of all pins will be done on adaptor.Finalize()
+
+		close(h.delayMicroSecChan)
+
+		return nil
+	}
+
+	return &h
+}
+
+// MeasureDistance retrieves the distance in front of sensor in meters and returns the measure. It is not designed
+// to work in a fast loop! For this specific usage, use StartDistanceMonitor() associated with Distance() instead.
+func (h *HCSR04Driver) MeasureDistance() (float64, error) {
+	err := h.measureDistance()
+	if err != nil {
+		return 0, err
+	}
+	return h.Distance(), nil
+}
+
+// Distance returns the last distance measured in meter, it does not trigger a distance measurement
+func (h *HCSR04Driver) Distance() float64 {
+	distMm := h.lastMeasureMicroSec * hcsr04SoundSpeed / 1000 / 2
+	return float64(distMm) / 1000.0
+}
+
+// StartDistanceMonitor starts continuous measurement. The current value can be read by Distance()
+func (h *HCSR04Driver) StartDistanceMonitor() error {
+	// ensure that start and stop can not interfere
+	h.mutex.Lock()
+	defer h.mutex.Unlock()
+
+	if h.distanceMonitorStopChan != nil {
+		return fmt.Errorf("distance monitor already started for '%s'", h.name)
+	}
+
+	h.distanceMonitorStopChan = make(chan struct{})
+	h.distanceMonitorStopWaitGroup = &sync.WaitGroup{}
+	h.distanceMonitorStopWaitGroup.Add(1)
+
+	go func(name string) {
+		defer h.distanceMonitorStopWaitGroup.Done()
+		for {
+			select {
+			case <-h.distanceMonitorStopChan:
+				h.distanceMonitorStopChan = nil
+				return
+			default:
+				if err := h.measureDistance(); err != nil {
+					fmt.Printf("continuous measure distance skipped for '%s': %v\n", name, err)
+				}
+				time.Sleep(hcsr04MonitorUpdate)
+			}
+		}
+	}(h.name)
+
+	return nil
+}
+
+// StopDistanceMonitor stop the monitor process
+func (h *HCSR04Driver) StopDistanceMonitor() error {
+	// ensure that start and stop can not interfere
+	h.mutex.Lock()
+	defer h.mutex.Unlock()
+
+	return h.stopDistanceMonitor()
+}
+
+func (h *HCSR04Driver) createEventHandler() func(int, time.Duration, string, uint32, uint32) {
+	var startTimestamp time.Duration
+	return func(offset int, t time.Duration, et string, sn uint32, lsn uint32) {
+		switch et {
+		case system.DigitalPinEventRisingEdge:
+			startTimestamp = t
+		case system.DigitalPinEventFallingEdge:
+			// unfortunately there is an additional falling edge at each start trigger, so we need to filter this
+			// we use the start duration value for filtering
+			if startTimestamp == 0 {
+				return
+			}
+			h.delayMicroSecChan <- (t - startTimestamp).Microseconds()
+			startTimestamp = 0
+		}
+	}
+}
+
+func (h *HCSR04Driver) stopDistanceMonitor() error {
+	if h.distanceMonitorStopChan == nil {
+		return fmt.Errorf("distance monitor is not yet started for '%s'", h.name)
+	}
+
+	h.distanceMonitorStopChan <- struct{}{}
+	h.distanceMonitorStopWaitGroup.Wait()
+
+	return nil
+}
+
+func (h *HCSR04Driver) measureDistance() error {
+	h.measureMutex.Lock()
+	defer h.measureMutex.Unlock()
+
+	if err := h.emitTrigger(); err != nil {
+		return err
+	}
+
+	// stop the loop if the measure is done or the timeout is elapsed
+	timeout := hcsr04StartTransmitTimeout + hcsr04ReceiveTimeout
+	select {
+	case <-time.After(timeout):
+		return fmt.Errorf("timeout %s reached while waiting for value with echo pin %s", timeout, h.echoPinID)
+	case h.lastMeasureMicroSec = <-h.delayMicroSecChan:
+	}
+
+	return nil
+}
+
+func (h *HCSR04Driver) emitTrigger() error {
+	if err := h.triggerPin.Write(1); err != nil {
+		return err
+	}
+	time.Sleep(hcsr04EmitTriggerDuration)
+	return h.triggerPin.Write(0)
+}

drivers/gpio/hcsr04_driver_test.go

@@ -0,0 +1,338 @@
+package gpio
+
+import (
+	"fmt"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gobot.io/x/gobot/v2/system"
+)
+
+func initTestHCSR04DriverWithStubbedAdaptor(triggerPinID string, echoPinID string) (*HCSR04Driver, *digitalPinMock) {
+	a := newGpioTestAdaptor()
+	tpin := a.addDigitalPin(triggerPinID)
+	_ = a.addDigitalPin(echoPinID)
+	d := NewHCSR04Driver(a, triggerPinID, echoPinID, false)
+	if err := d.Start(); err != nil {
+		panic(err)
+	}
+	return d, tpin
+}
+
+func TestNewHCSR04Driver(t *testing.T) {
+	// arrange
+	const (
+		triggerPinID = "3"
+		echoPinID    = "4"
+	)
+	a := newGpioTestAdaptor()
+	tpin := a.addDigitalPin(triggerPinID)
+	epin := a.addDigitalPin(echoPinID)
+	// act
+	d := NewHCSR04Driver(a, triggerPinID, echoPinID, false)
+	// assert
+	assert.IsType(t, &HCSR04Driver{}, d)
+	assert.NotNil(t, d.Driver)
+	assert.True(t, strings.HasPrefix(d.name, "HCSR04"))
+	assert.Equal(t, a, d.connection)
+	assert.NoError(t, d.afterStart())
+	assert.NoError(t, d.beforeHalt())
+	assert.NotNil(t, d.Commander)
+	assert.NotNil(t, d.mutex)
+	assert.Equal(t, triggerPinID, d.triggerPinID)
+	assert.Equal(t, echoPinID, d.echoPinID)
+	assert.Equal(t, false, d.useEdgePolling)
+	assert.Equal(t, tpin, d.triggerPin)
+	assert.Equal(t, epin, d.echoPin)
+}
+
+func TestHCSR04MeasureDistance(t *testing.T) {
+	tests := map[string]struct {
+		measureMicroSec  int64
+		simulateWriteErr string
+		wantCallsWrite   int
+		wantVal          float64
+		wantErr          string
+	}{
+		"measure_ok": {
+			measureMicroSec: 5831,
+			wantCallsWrite:  2,
+			wantVal:         1.0,
+		},
+		"error_timeout": {
+			measureMicroSec: 170000, // > 160 ms
+			wantCallsWrite:  2,
+			wantErr:         "timeout 160ms reached",
+		},
+		"error_write": {
+			measureMicroSec:  5831,
+			simulateWriteErr: "write error",
+			wantCallsWrite:   1,
+			wantErr:          "write error",
+		},
+	}
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			// arrange
+			d, tpin := initTestHCSR04DriverWithStubbedAdaptor("3", "4")
+			// arrange sensor and event handler simulation
+			waitForTriggerChan := make(chan struct{})
+			loopWg := sync.WaitGroup{}
+			defer func() {
+				close(waitForTriggerChan)
+				loopWg.Wait()
+			}()
+			loopWg.Add(1)
+			go func() {
+				<-waitForTriggerChan
+				m := tc.measureMicroSec // to prevent data race together with wait group
+				loopWg.Done()
+				time.Sleep(time.Duration(m) * time.Microsecond)
+				d.delayMicroSecChan <- m
+			}()
+			// arrange writes
+			numCallsWrite := 0
+			var oldVal int
+			tpin.writeFunc = func(val int) error {
+				numCallsWrite++
+				if val == 0 && oldVal == 1 {
+					// falling edge detected
+					waitForTriggerChan <- struct{}{}
+				}
+				oldVal = val
+				var err error
+				if tc.simulateWriteErr != "" {
+					err = fmt.Errorf(tc.simulateWriteErr)
+				}
+				return err
+			}
+			// act
+			got, err := d.MeasureDistance()
+			// assert
+			assert.Equal(t, tc.wantCallsWrite, numCallsWrite)
+			if tc.wantErr != "" {
+				assert.ErrorContains(t, err, tc.wantErr)
+			} else {
+				require.NoError(t, err)
+			}
+			assert.Equal(t, tc.wantVal, got)
+		})
+	}
+}
+
+func TestHCSR04Distance(t *testing.T) {
+	tests := map[string]struct {
+		measureMicroSec  int64
+		simulateWriteErr string
+		wantVal          float64
+		wantErr          string
+	}{
+		"distance_0mm": {
+			measureMicroSec: 0, // no validity test yet
+			wantVal:         0.0,
+		},
+		"distance_2cm": {
+			measureMicroSec: 117, // 117us ~ 0.12ms => ~2cm
+			wantVal:         0.02,
+		},
+		"distance_4m": {
+			measureMicroSec: 23324, // 23324us ~ 24ms => ~4m
+			wantVal:         4.0,
+		},
+	}
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			// arrange
+			d := HCSR04Driver{lastMeasureMicroSec: tc.measureMicroSec}
+			// act
+			got := d.Distance()
+			// assert
+			assert.Equal(t, tc.wantVal, got)
+		})
+	}
+}
+
+func TestHCSR04StartDistanceMonitor(t *testing.T) {
+	tests := map[string]struct {
+		simulateIsStarted bool
+		simulateWriteErr  bool
+		wantErr           string
+	}{
+		"start_ok": {},
+		"start_ok_measure_error": {
+			simulateWriteErr: true,
+		},
+		"error_already_started": {
+			simulateIsStarted: true,
+			wantErr:           "already started for 'HCSR04-",
+		},
+	}
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			// arrange
+			d, tpin := initTestHCSR04DriverWithStubbedAdaptor("3", "4")
+			defer func() {
+				if d.distanceMonitorStopChan != nil {
+					close(d.distanceMonitorStopChan)
+				}
+				if d.distanceMonitorStopWaitGroup != nil {
+					d.distanceMonitorStopWaitGroup.Wait()
+				}
+			}()
+			if tc.simulateIsStarted {
+				d.distanceMonitorStopChan = make(chan struct{})
+			}
+			tpin.writeFunc = func(val int) error {
+				if tc.simulateWriteErr {
+					return fmt.Errorf("write error")
+				}
+				return nil
+			}
+			// act
+			err := d.StartDistanceMonitor()
+			time.Sleep(1 * time.Millisecond) // < 160 ms
+			// assert
+			if tc.wantErr != "" {
+				assert.ErrorContains(t, err, tc.wantErr)
+			} else {
+				require.NoError(t, err)
+				assert.NotNil(t, d.distanceMonitorStopChan)
+				assert.NotNil(t, d.distanceMonitorStopWaitGroup)
+			}
+		})
+	}
+}
+
+func TestHCSR04StopDistanceMonitor(t *testing.T) {
+	tests := map[string]struct {
+		start   bool
+		wantErr string
+	}{
+		"stop_ok": {
+			start: true,
+		},
+		"error_not_started": {
+			wantErr: "not yet started for 'HCSR04-",
+		},
+	}
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			// arrange
+			d, _ := initTestHCSR04DriverWithStubbedAdaptor("3", "4")
+			defer func() {
+				if d.distanceMonitorStopChan != nil {
+					close(d.distanceMonitorStopChan)
+				}
+				if d.distanceMonitorStopWaitGroup != nil {
+					d.distanceMonitorStopWaitGroup.Wait()
+				}
+			}()
+			if tc.start {
+				err := d.StartDistanceMonitor()
+				require.NoError(t, err)
+			}
+			// act
+			err := d.StopDistanceMonitor()
+			time.Sleep(1 * time.Millisecond) // < 160 ms
+			// assert
+			if tc.wantErr != "" {
+				assert.ErrorContains(t, err, tc.wantErr)
+			} else {
+				require.NoError(t, err)
+				assert.Nil(t, d.distanceMonitorStopChan)
+			}
+		})
+	}
+}
+
+func TestHCSR04_createEventHandler(t *testing.T) {
+	type eventCall struct {
+		timeStamp time.Duration
+		eventType string
+	}
+	tests := map[string]struct {
+		calls []eventCall
+		wants []int64
+	}{
+		"only_rising": {
+			calls: []eventCall{
+				{timeStamp: 1 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 2 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+			},
+		},
+		"only_falling": {
+			calls: []eventCall{
+				{timeStamp: 2 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+				{timeStamp: 3 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+			},
+		},
+		"event_normal": {
+			calls: []eventCall{
+				{timeStamp: 1 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 10 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+			},
+			wants: []int64{9},
+		},
+		"event_falling_before": {
+			calls: []eventCall{
+				{timeStamp: 1 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+				{timeStamp: 2 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 10 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+			},
+			wants: []int64{8},
+		},
+		"event_falling_after": {
+			calls: []eventCall{
+				{timeStamp: 1 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 10 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+				{timeStamp: 12 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+			},
+			wants: []int64{9},
+		},
+		"event_rising_before": {
+			calls: []eventCall{
+				{timeStamp: 1 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 5 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 10 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+			},
+			wants: []int64{5},
+		},
+		"event_rising_after": {
+			calls: []eventCall{
+				{timeStamp: 1 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 10 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+				{timeStamp: 12 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+			},
+			wants: []int64{9},
+		},
+		"event_multiple": {
+			calls: []eventCall{
+				{timeStamp: 1 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 10 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+				{timeStamp: 11 * time.Microsecond, eventType: system.DigitalPinEventRisingEdge},
+				{timeStamp: 13 * time.Microsecond, eventType: system.DigitalPinEventFallingEdge},
+			},
+			wants: []int64{9, 2},
+		},
+	}
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			// arrange
+			d := HCSR04Driver{delayMicroSecChan: make(chan int64, len(tc.wants))}
+			// act
+			eh := d.createEventHandler()
+			for _, call := range tc.calls {
+				eh(0, call.timeStamp, call.eventType, 0, 0)
+			}
+			// assert
+			for _, want := range tc.wants {
+				got := <-d.delayMicroSecChan
+				assert.Equal(t, want, got)
+			}
+		})
+	}
+}

drivers/gpio/helpers_test.go

@@ -1,6 +1,11 @@
 package gpio
 
-import "sync"
+import (
+	"fmt"
+	"sync"
+
+	"gobot.io/x/gobot/v2"
+)
 
 type gpioTestBareAdaptor struct{}
 
@@ -9,8 +14,13 @@ func (t *gpioTestBareAdaptor) Finalize() (err error) { return }
 func (t *gpioTestBareAdaptor) Name() string          { return "" }
 func (t *gpioTestBareAdaptor) SetName(n string)      {}
 
+type digitalPinMock struct {
+	writeFunc func(val int) (err error)
+}
+
 type gpioTestAdaptor struct {
 	name             string
+	pinMap           map[string]gobot.DigitalPinner
 	port             string
 	mtx              sync.Mutex
 	digitalReadFunc  func(ping string) (val int, err error)
@@ -22,6 +32,7 @@ type gpioTestAdaptor struct {
 func newGpioTestAdaptor() *gpioTestAdaptor {
 	t := gpioTestAdaptor{
 		name:   "gpio_test_adaptor",
+		pinMap: make(map[string]gobot.DigitalPinner),
 		port:   "/dev/null",
 		digitalWriteFunc: func(pin string, val byte) (err error) {
 			return nil
@@ -73,3 +84,44 @@ func (t *gpioTestAdaptor) Finalize() (err error) { return }
 func (t *gpioTestAdaptor) Name() string          { return t.name }
 func (t *gpioTestAdaptor) SetName(n string)      { t.name = n }
 func (t *gpioTestAdaptor) Port() string          { return t.port }
+
+// DigitalPin (interface DigitalPinnerProvider) return a pin object
+func (t *gpioTestAdaptor) DigitalPin(id string) (gobot.DigitalPinner, error) {
+	if pin, ok := t.pinMap[id]; ok {
+		return pin, nil
+	}
+	return nil, fmt.Errorf("pin '%s' not found in '%s'", id, t.name)
+}
+
+// ApplyOptions (interface DigitalPinOptionApplier by DigitalPinner) apply all given options to the pin immediately
+func (d *digitalPinMock) ApplyOptions(options ...func(gobot.DigitalPinOptioner) bool) error {
+	return nil
+}
+
+// Export (interface DigitalPinner) exports the pin for use by the adaptor
+func (d *digitalPinMock) Export() error {
+	return nil
+}
+
+// Unexport (interface DigitalPinner) releases the pin from the adaptor, so it is free for the operating system
+func (d *digitalPinMock) Unexport() error {
+	return nil
+}
+
+// Read (interface DigitalPinner) reads the current value of the pin
+func (d *digitalPinMock) Read() (n int, err error) {
+	return 0, err
+}
+
+// Write (interface DigitalPinner) writes to the pin
+func (d *digitalPinMock) Write(b int) error {
+	return d.writeFunc(b)
+}
+
+func (t *gpioTestAdaptor) addDigitalPin(id string) *digitalPinMock {
+	dpm := &digitalPinMock{
+		writeFunc: func(val int) (err error) { return nil },
+	}
+	t.pinMap[id] = dpm
+	return dpm
+}

examples/raspi_hcsr04.go

@@ -0,0 +1,89 @@
+//go:build example
+// +build example
+
+//
+// Do not build by default.
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"gobot.io/x/gobot/v2"
+	"gobot.io/x/gobot/v2/drivers/gpio"
+	"gobot.io/x/gobot/v2/platforms/raspi"
+)
+
+func main() {
+	const (
+		triggerOutput = "11"
+		echoInput     = "13"
+	)
+
+	// this is mandatory for systems with defunct edge detection, although the "cdev" is used with an newer Kernel
+	// keep in mind, that this cause more inaccurate measurements
+	const pollEdgeDetection = true
+
+	a := raspi.NewAdaptor()
+	hcsr04 := gpio.NewHCSR04Driver(a, triggerOutput, echoInput, pollEdgeDetection)
+
+	work := func() {
+		if pollEdgeDetection {
+			fmt.Println("Please note that measurements are CPU consuming and will be more inaccurate with this setting.")
+			fmt.Println("After startup the system is under load and the measurement is very inaccurate, so wait a bit...")
+			time.Sleep(2000 * time.Millisecond)
+		}
+
+		if err := hcsr04.StartDistanceMonitor(); err != nil {
+			log.Fatal(err)
+		}
+
+		// first single shot
+		if v, err := hcsr04.MeasureDistance(); err != nil {
+			log.Fatal(err)
+		} else {
+			fmt.Printf("first single shot done: %5.3f m\n", v)
+		}
+
+		ticker := gobot.Every(1*time.Second, func() {
+			fmt.Printf("continuous measurement: %5.3f m\n", hcsr04.Distance())
+		})
+
+		gobot.After(5*time.Second, func() {
+			if err := hcsr04.StopDistanceMonitor(); err != nil {
+				log.Fatal(err)
+			}
+			ticker.Stop()
+		})
+
+		gobot.After(7*time.Second, func() {
+			// second single shot
+			if v, err := hcsr04.MeasureDistance(); err != nil {
+				log.Fatal(err)
+			} else {
+				fmt.Printf("second single shot done: %5.3f m\n", v)
+			}
+			// cleanup
+			if err := hcsr04.Halt(); err != nil {
+				log.Println(err)
+			}
+			if err := a.Finalize(); err != nil {
+				log.Println(err)
+			}
+			os.Exit(0)
+		})
+	}
+
+	robot := gobot.NewRobot("distanceBot",
+		[]gobot.Connection{a},
+		[]gobot.Device{hcsr04},
+		work,
+	)
+
+	if err := robot.Start(); err != nil {
+		log.Fatal(err)
+	}
+}

examples/tinkerboard_hcsr04.go

@@ -0,0 +1,93 @@
+//go:build example
+// +build example
+
+//
+// Do not build by default.
+
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"time"
+
+	"gobot.io/x/gobot/v2"
+	"gobot.io/x/gobot/v2/drivers/gpio"
+	"gobot.io/x/gobot/v2/platforms/tinkerboard"
+)
+
+// Wiring
+// PWR  Tinkerboard: 2(+5V), 6, 9, 14, 20 (GND)
+// GPIO Tinkerboard: header pin 7 is the trigger output, pin 22 used as echo input
+// HC-SR04: the power is wired to +5V and GND of tinkerboard, the same for trigger output and the echo input pin
+func main() {
+	const (
+		triggerOutput = "7"
+		echoInput     = "22"
+	)
+
+	// this is mandatory for systems with defunct edge detection, although the "cdev" is used with an newer Kernel
+	// keep in mind, that this cause more inaccurate measurements
+	const pollEdgeDetection = true
+
+	a := tinkerboard.NewAdaptor()
+	hcsr04 := gpio.NewHCSR04Driver(a, triggerOutput, echoInput, pollEdgeDetection)
+
+	work := func() {
+		if pollEdgeDetection {
+			fmt.Println("Please note that measurements are CPU consuming and will be more inaccurate with this setting.")
+			fmt.Println("After startup the system is under load and the measurement is very inaccurate, so wait a bit...")
+			time.Sleep(2000 * time.Millisecond)
+		}
+
+		if err := hcsr04.StartDistanceMonitor(); err != nil {
+			log.Fatal(err)
+		}
+
+		// first single shot
+		if v, err := hcsr04.MeasureDistance(); err != nil {
+			log.Fatal(err)
+		} else {
+			fmt.Printf("first single shot done: %5.3f m\n", v)
+		}
+
+		ticker := gobot.Every(1*time.Second, func() {
+			fmt.Printf("continuous measurement: %5.3f m\n", hcsr04.Distance())
+		})
+
+		gobot.After(5*time.Second, func() {
+			if err := hcsr04.StopDistanceMonitor(); err != nil {
+				log.Fatal(err)
+			}
+			ticker.Stop()
+		})
+
+		gobot.After(7*time.Second, func() {
+			// second single shot
+			if v, err := hcsr04.MeasureDistance(); err != nil {
+				log.Fatal(err)
+			} else {
+				fmt.Printf("second single shot done: %5.3f m\n", v)
+			}
+			// cleanup
+			if err := hcsr04.Halt(); err != nil {
+				log.Println(err)
+			}
+			if err := a.Finalize(); err != nil {
+				log.Println(err)
+			}
+			os.Exit(0)
+		})
+	}
+
+	robot := gobot.NewRobot("distanceBot",
+		[]gobot.Connection{a},
+		[]gobot.Device{hcsr04},
+		work,
+	)
+
+	if err := robot.Start(); err != nil {
+		log.Fatal(err)
+	}
+}

platforms/adaptors/digitalpinsadaptor.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/hashicorp/go-multierror"
+
 	"gobot.io/x/gobot/v2"
 	"gobot.io/x/gobot/v2/system"
 )
@@ -31,6 +32,7 @@ type digitalPinsOptioner interface {
 		detectedEdge string, seqno uint32, lseqno uint32))
 	prepareDigitalPinEventOnBothEdges(pin string, handler func(lineOffset int, timestamp time.Duration,
 		detectedEdge string, seqno uint32, lseqno uint32))
+	prepareDigitalPinPollForEdgeDetection(pin string, pollInterval time.Duration, pollQuitChan chan struct{})
 }
 
 // DigitalPinsAdaptor is a adaptor for digital pins, normally used for composition in platforms.
@@ -196,6 +198,17 @@ func WithGpioEventOnBothEdges(pin string, handler func(lineOffset int, timestamp
 	}
 }
 
+// WithGpioPollForEdgeDetection prepares the given input pin to use a discrete input pin polling function together with
+// edge detection.
+func WithGpioPollForEdgeDetection(pin string, pollInterval time.Duration, pollQuitChan chan struct{}) func(Optioner) {
+	return func(o Optioner) {
+		a, ok := o.(digitalPinsOptioner)
+		if ok {
+			a.prepareDigitalPinPollForEdgeDetection(pin, pollInterval, pollQuitChan)
+		}
+	}
+}
+
 // Connect prepare new connection to digital pins.
 func (a *DigitalPinsAdaptor) Connect() error {
 	a.mutex.Lock()
@@ -370,6 +383,18 @@ func (a *DigitalPinsAdaptor) prepareDigitalPinEventOnBothEdges(id string, handle
 	a.pinOptions[id] = append(a.pinOptions[id], system.WithPinEventOnBothEdges(handler))
 }
 
+func (a *DigitalPinsAdaptor) prepareDigitalPinPollForEdgeDetection(
+	id string,
+	pollInterval time.Duration,
+	pollQuitChan chan struct{},
+) {
+	if a.pinOptions == nil {
+		a.pinOptions = make(map[string][]func(gobot.DigitalPinOptioner) bool)
+	}
+
+	a.pinOptions[id] = append(a.pinOptions[id], system.WithPinPollForEdgeDetection(pollInterval, pollQuitChan))
+}
+
 func (a *DigitalPinsAdaptor) digitalPin(id string, opts ...func(gobot.DigitalPinOptioner) bool) (gobot.DigitalPinner, error) {
 	if a.pins == nil {
 		return nil, fmt.Errorf("not connected for pin %s", id)

platforms/adaptors/digitalpinsadaptor_test.go

@@ -215,6 +215,7 @@ func TestDigitalWrite(t *testing.T) {
 	WithGpiosPullUp("7")(a)
 	WithGpiosOpenDrain("7")(a)
 	WithGpioEventOnFallingEdge("7", gpioEventHandler)(a)
+	WithGpioPollForEdgeDetection("7", 0, nil)(a)
 	err := a.DigitalWrite("7", 1)
 	assert.NoError(t, err)
 	assert.Equal(t, "1", fs.Files["/sys/class/gpio/gpio18/value"].Contents)

platforms/firmata/firmata_adaptor.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 package firmata
 
 import (

platforms/firmata/firmata_adaptor_test.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 package firmata
 
 import (

platforms/firmata/firmata_i2c.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 package firmata
 
 import (

platforms/firmata/firmata_i2c_test.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 package firmata
 
 import (

platforms/firmata/tcp_firmata_adaptor.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 package firmata
 
 import (

platforms/firmata/tcp_firmata_adaptor_test.go

@@ -1,3 +1,6 @@
+//go:build !windows
+// +build !windows
+
 package firmata
 
 import (