led: support led functionality on the bbb

bbb.go

@@ -16,6 +16,9 @@ func init() {
 				return newGPIODriver(bbbPins, newDigitalPin, newBBBAnalogPin)
 			},
 			I2C: newI2CDriver,
+			LEDDriver: func() LEDDriver {
+				return newLEDDriver(bbbLEDMap)
+			},
 		}
 	}
 }
@@ -88,6 +91,13 @@ var bbbPins = PinMap{
 	&PinDesc{ID: "P9_40", Aliases: []string{"1", "AIN1"}, Caps: CapAnalog, AnalogLogical: 1},
 }
 
+var bbbLEDMap = LEDMap{
+	"beaglebone:green:usr0": []string{"0", "USR0", "usr0"},
+	"beaglebone:green:usr1": []string{"1", "USR1", "usr1"},
+	"beaglebone:green:usr2": []string{"2", "USR2", "usr2"},
+	"beaglebone:green:usr3": []string{"3", "USR3", "usr3"},
+}
+
 type bbbAnalogPin struct {
 	n int
 

descriptor.go

@@ -1,10 +1,14 @@
 package embd
 
-import "fmt"
+import (
+	"errors"
+	"fmt"
+)
 
 type Descriptor struct {
-	GPIO func() GPIO
-	I2C  func() I2C
+	GPIO      func() GPIO
+	I2C       func() I2C
+	LEDDriver func() LEDDriver
 }
 
 type Describer func(rev int) *Descriptor
@@ -24,3 +28,5 @@ func DescribeHost() (*Descriptor, error) {
 
 	return describer(rev), nil
 }
+
+var ErrFeatureNotSupport = errors.New("embd: feature is not supported")

gpio.go

@@ -51,6 +51,10 @@ func InitGPIO() error {
 		return err
 	}
 
+	if desc.GPIO == nil {
+		return ErrFeatureNotSupport
+	}
+
 	gpioInstance = desc.GPIO()
 
 	return nil

i2c.go

@@ -37,6 +37,10 @@ func InitI2C() error {
 		return err
 	}
 
+	if desc.I2C == nil {
+		return ErrFeatureNotSupport
+	}
+
 	i2cInstance = desc.I2C()
 
 	return nil

led.go

@@ -0,0 +1,59 @@
+package embd
+
+type LED interface {
+	On() error
+	Off() error
+
+	Toggle() error
+
+	Close() error
+}
+
+type LEDDriver interface {
+	LED(key interface{}) (LED, error)
+
+	Close() error
+}
+
+var ledDriverInstance LEDDriver
+
+func InitLED() error {
+	desc, err := DescribeHost()
+	if err != nil {
+		return err
+	}
+
+	if desc.LEDDriver == nil {
+		return ErrFeatureNotSupport
+	}
+
+	ledDriverInstance = desc.LEDDriver()
+
+	return nil
+}
+
+func CloseLED() error {
+	return ledDriverInstance.Close()
+}
+
+func NewLED(key interface{}) (LED, error) {
+	return ledDriverInstance.LED(key)
+}
+
+func LEDOn(key interface{}) error {
+	led, err := NewLED(key)
+	if err != nil {
+		return err
+	}
+
+	return led.On()
+}
+
+func LEDOff(key interface{}) error {
+	led, err := NewLED(key)
+	if err != nil {
+		return err
+	}
+
+	return led.Off()
+}

leddriver.go

@@ -0,0 +1,172 @@
+package embd
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strconv"
+	"strings"
+)
+
+type LEDMap map[string][]string
+
+type ledDriver struct {
+	ledMap LEDMap
+
+	initializedLEDs map[string]LED
+}
+
+func newLEDDriver(ledMap LEDMap) LEDDriver {
+	return &ledDriver{
+		ledMap:          ledMap,
+		initializedLEDs: map[string]LED{},
+	}
+}
+
+func (d *ledDriver) lookup(k interface{}) (string, error) {
+	var ks string
+	switch key := k.(type) {
+	case int:
+		ks = strconv.Itoa(key)
+	case string:
+		ks = key
+	case fmt.Stringer:
+		ks = key.String()
+	default:
+		return "", errors.New("led: invalid key type")
+	}
+
+	for id := range d.ledMap {
+		for _, alias := range d.ledMap[id] {
+			if alias == ks {
+				return id, nil
+			}
+		}
+	}
+
+	return "", fmt.Errorf("led: no match found for %q", k)
+}
+
+func (d *ledDriver) LED(k interface{}) (LED, error) {
+	id, err := d.lookup(k)
+	if err != nil {
+		return nil, err
+	}
+
+	led := newLED(id)
+	d.initializedLEDs[id] = led
+
+	return led, nil
+}
+
+func (d *ledDriver) Close() error {
+	for _, led := range d.initializedLEDs {
+		if err := led.Close(); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+type led struct {
+	id string
+
+	brightness *os.File
+
+	initialized bool
+}
+
+func newLED(id string) LED {
+	return &led{id: id}
+}
+
+func (l *led) init() error {
+	if l.initialized {
+		return nil
+	}
+
+	var err error
+	if l.brightness, err = l.brightnessFile(); err != nil {
+		return err
+	}
+
+	l.initialized = true
+
+	return nil
+}
+
+func (l *led) brightnessFilePath() string {
+	return fmt.Sprintf("/sys/class/leds/%v/brightness", l.id)
+}
+
+func (l *led) openFile(path string) (*os.File, error) {
+	return os.OpenFile(path, os.O_RDWR, os.ModeExclusive)
+}
+
+func (l *led) brightnessFile() (*os.File, error) {
+	return l.openFile(l.brightnessFilePath())
+}
+
+func (l *led) On() error {
+	if err := l.init(); err != nil {
+		return err
+	}
+
+	_, err := l.brightness.WriteString("1")
+	return err
+}
+
+func (l *led) Off() error {
+	if err := l.init(); err != nil {
+		return err
+	}
+
+	_, err := l.brightness.WriteString("0")
+	return err
+}
+
+func (l *led) isOn() (bool, error) {
+	l.brightness.Seek(0, 0)
+	bytes, err := ioutil.ReadAll(l.brightness)
+	if err != nil {
+		return false, err
+	}
+	str := string(bytes)
+	str = strings.TrimSpace(str)
+	if str == "1" {
+		return true, nil
+	}
+	return false, nil
+}
+
+func (l *led) Toggle() error {
+	if err := l.init(); err != nil {
+		return err
+	}
+
+	state, err := l.isOn()
+	if err != nil {
+		return err
+	}
+
+	if state {
+		return l.Off()
+	}
+	return l.On()
+}
+
+func (l *led) Close() error {
+	if !l.initialized {
+		return nil
+	}
+
+	if err := l.brightness.Close(); err != nil {
+		return err
+	}
+
+	l.initialized = false
+
+	return nil
+}

samples/.gitignore

@@ -8,6 +8,8 @@ gpiodetect
 gpiodirect
 gpioshort
 l3gd20
+led
+ledshort
 lsm303
 mcp4725
 pca9685

samples/led.go

@@ -0,0 +1,44 @@
+// +build ignore
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"time"
+
+	"github.com/kidoman/embd"
+)
+
+func main() {
+	if err := embd.InitLED(); err != nil {
+		panic(err)
+	}
+	defer embd.CloseLED()
+
+	led, err := embd.NewLED(3)
+	if err != nil {
+		panic(err)
+	}
+	defer func() {
+		led.Off()
+		led.Close()
+	}()
+
+	quit := make(chan os.Signal, 1)
+	signal.Notify(quit, os.Interrupt, os.Kill)
+	defer signal.Stop(quit)
+
+	for {
+		select {
+		case <-time.After(500 * time.Millisecond):
+			if err := led.Toggle(); err != nil {
+				panic(err)
+			}
+			fmt.Printf("Toggled\n")
+		case <-quit:
+			return
+		}
+	}
+}

samples/ledshort.go

@@ -0,0 +1,18 @@
+// +build ignore
+
+package main
+
+import (
+	"time"
+
+	"github.com/kidoman/embd"
+)
+
+func main() {
+	embd.InitLED()
+	defer embd.CloseLED()
+
+	embd.LEDOn(3)
+	time.Sleep(1 * time.Second)
+	embd.LEDOff(3)
+}