Refactor pwm operations

platforms/beaglebone/beaglebone_adaptor.go

@@ -206,8 +206,8 @@ func (b *BeagleboneAdaptor) ServoWrite(pin string, val byte) (err error) {
 	if err != nil {
 		return err
 	}
-	period := 20000000.0
+	period := 16666666.0
-	duty := gobot.FromScale(float64(^val), 0, 180.0)
+	duty := (gobot.FromScale(float64(val), 0, 180.0) * 0.115) + 0.05
 	return b.pwmPins[i].pwmWrite(strconv.Itoa(int(period)), strconv.Itoa(int(period*duty)))
 }
 
@@ -359,7 +359,7 @@ func (b *BeagleboneAdaptor) pwmWrite(pin string, val byte) (err error) {
 		return
 	}
 	period := 500000.0
-	duty := gobot.FromScale(float64(^val), 0, 255.0)
+	duty := gobot.FromScale(float64(val), 0, 255.0)
 	return b.pwmPins[i].pwmWrite(strconv.Itoa(int(period)), strconv.Itoa(int(period*duty)))
 }
 
@@ -384,10 +384,7 @@ func ensureSlot(slots, item string) (err error) {
 	if err != nil {
 		return err
 	}
-	err = fi.Sync()
+	fi.Sync()
-	if err != nil {
-		return err
-	}
 
 	scanner = bufio.NewScanner(fi)
 	for scanner.Scan() {

platforms/beaglebone/beaglebone_adaptor_test.go

@@ -23,6 +23,7 @@ func TestBeagleboneAdaptor(t *testing.T) {
 		"/sys/devices/ocp.3/pwm_test_P9_14.5",
 		"/sys/devices/ocp.3/pwm_test_P9_14.5/run",
 		"/sys/devices/ocp.3/pwm_test_P9_14.5/period",
+		"/sys/devices/ocp.3/pwm_test_P9_14.5/polarity",
 		"/sys/devices/ocp.3/pwm_test_P9_14.5/duty",
 		"/sys/class/gpio/export",
 		"/sys/class/gpio/unexport",
@@ -57,19 +58,19 @@ func TestBeagleboneAdaptor(t *testing.T) {
 	gobot.Assert(
 		t,
 		fs.Files["/sys/devices/ocp.3/pwm_test_P9_14.5/duty"].Contents,
-		"156862",
+		"343137",
 	)
 
 	a.ServoWrite("P9_14", 100)
 	gobot.Assert(
 		t,
 		fs.Files["/sys/devices/ocp.3/pwm_test_P9_14.5/period"].Contents,
-		"20000000",
+		"16666666",
 	)
 	gobot.Assert(
 		t,
 		fs.Files["/sys/devices/ocp.3/pwm_test_P9_14.5/duty"].Contents,
-		"17222222",
+		"1898148",
 	)
 
 	// Analog

platforms/beaglebone/pwm_pin.go

@@ -1,9 +1,11 @@
 package beaglebone
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/hybridgroup/gobot/sysfs"
 )
@@ -15,8 +17,7 @@ type pwmPin struct {
 
 // newPwmPin creates a new pwm pin with specified pin number
 func newPwmPin(pinNum string, ocp string) (p *pwmPin, err error) {
-	var fi sysfs.File
+	done := make(chan error, 0)
-
 	p = &pwmPin{
 		pinNum: strings.ToUpper(pinNum),
 	}
@@ -28,36 +29,51 @@ func newPwmPin(pinNum string, ocp string) (p *pwmPin, err error) {
 
 	p.pwmDevice = pwmDevice[0]
 
-	for i := 0; i < 10; i++ {
+	go func() {
-		fi, err = sysfs.OpenFile(fmt.Sprintf("%v/run", p.pwmDevice), os.O_RDWR|os.O_APPEND, 0666)
+		for {
-		defer fi.Close()
+			if _, err := sysfs.OpenFile(fmt.Sprintf("%v/period", p.pwmDevice), os.O_RDONLY, 0644); err == nil {
-		if err != nil && i == 9 {
+				break
-			return
+			}
-		} else {
-			break
 		}
-	}
+		for {
+			if fi, err := sysfs.OpenFile(fmt.Sprintf("%v/duty", p.pwmDevice), os.O_WRONLY|os.O_APPEND, 0644); err == nil {
+				defer fi.Close()
+				if _, err = fi.WriteString("0"); err != nil {
+					done <- err
+				}
+				fi.Sync()
+				break
+			}
+		}
+		for {
+			if fi, err := sysfs.OpenFile(fmt.Sprintf("%v/polarity", p.pwmDevice), os.O_WRONLY|os.O_APPEND, 0644); err == nil {
+				defer fi.Close()
+				if _, err = fi.WriteString("0"); err != nil {
+					done <- err
+				}
+				fi.Sync()
+				break
+			}
+		}
+		for {
+			if fi, err := sysfs.OpenFile(fmt.Sprintf("%v/run", p.pwmDevice), os.O_WRONLY|os.O_APPEND, 0644); err == nil {
+				defer fi.Close()
+				if _, err = fi.WriteString("1"); err != nil {
+					done <- err
+				}
+				fi.Sync()
+				break
+			}
+		}
+		done <- nil
+	}()
 
-	_, err = fi.WriteString("1")
+	select {
-	if err != nil {
+	case err = <-done:
-		return
+		return p, err
+	case <-time.After(500 * time.Millisecond):
+		return p, errors.New("could not initialize pwm device")
 	}
-	err = fi.Sync()
-	if err != nil {
-		return
-	}
-
-	for {
-		if _, err := sysfs.OpenFile(fmt.Sprintf("%v/period", p.pwmDevice), os.O_RDONLY, 0644); err == nil {
-			break
-		}
-	}
-	for {
-		if _, err := sysfs.OpenFile(fmt.Sprintf("%v/duty", p.pwmDevice), os.O_RDONLY, 0644); err == nil {
-			break
-		}
-	}
-	return
 }
 
 // pwmWrite writes to a pwm pin with specified period and duty
@@ -67,8 +83,7 @@ func (p *pwmPin) pwmWrite(period string, duty string) (err error) {
 	if err != nil {
 		return
 	}
-	_, err = f1.WriteString(period)
+	if _, err = f1.WriteString(period); err != nil {
-	if err != nil {
 		return
 	}
 
@@ -77,10 +92,8 @@ func (p *pwmPin) pwmWrite(period string, duty string) (err error) {
 	if err != nil {
 		return
 	}
+
 	_, err = f2.WriteString(duty)
-	if err != nil {
-		return
-	}
 
 	return
 }