Get I2C functionality before doing SMBus block I/O

In the sysfs i2cDevice implementation, use an ioctl to get the adapter
functionality mask. Prefer SMBus block I/O but if it's not available,
perform read/write calls directly on the file descriptor.

Improve Wiichuck error handling. Add a 1 ms delay between I/O operations
to the Wiichuck; this dramatically improves reliability.

Signed-off-by: Hrishikesh Tapaswi <[email protected]>

examples/chip_wiichuck.go

@@ -26,6 +26,9 @@ func main() {
 		gobot.On(wiichuck.Event("z"), func(data interface{}) {
 			fmt.Println("z")
 		})
+		gobot.On(wiichuck.Event("error"), func(data interface{}) {
+			fmt.Println("Wiichuck error:", data)
+		})
 	}
 
 	robot := gobot.NewRobot("chuck",

examples/firmata_wiichuck.go

@@ -26,6 +26,9 @@ func main() {
 		gobot.On(wiichuck.Event("z"), func(data interface{}) {
 			fmt.Println("z")
 		})
+		gobot.On(wiichuck.Event("error"), func(data interface{}) {
+			fmt.Println("Wiichuck error:", data)
+		})
 	}
 
 	robot := gobot.NewRobot("chuck",

platforms/i2c/wiichuck_driver.go

@@ -14,6 +14,7 @@ type WiichuckDriver struct {
 	name       string
 	connection I2c
 	interval   time.Duration
+	pauseTime  time.Duration
 	gobot.Eventer
 	joystick map[string]float64
 	data     map[string]float64
@@ -22,14 +23,16 @@ type WiichuckDriver struct {
 // NewWiichuckDriver creates a WiichuckDriver with specified i2c interface and name.
 //
 // It adds the following events:
-//	"z"- Get's triggered every interval amount of time if the z button is pressed
-//	"c" - Get's triggered every interval amount of time if the c button is pressed
-//	"joystick" - Get's triggered every "interval" amount of time if a joystick event occured, you can access values x, y
+//	"z"- Gets triggered every interval amount of time if the z button is pressed
+//	"c" - Gets triggered every interval amount of time if the c button is pressed
+//	"joystick" - Gets triggered every "interval" amount of time if a joystick event occured, you can access values x, y
+//	"error" - Gets triggered whenever the WiichuckDriver encounters an error
 func NewWiichuckDriver(a I2c, name string, v ...time.Duration) *WiichuckDriver {
 	w := &WiichuckDriver{
 		name:       name,
 		connection: a,
 		interval:   10 * time.Millisecond,
+		pauseTime:  1 * time.Millisecond,
 		Eventer:    gobot.NewEventer(),
 		joystick: map[string]float64{
 			"sy_origin": -1,
@@ -50,6 +53,7 @@ func NewWiichuckDriver(a I2c, name string, v ...time.Duration) *WiichuckDriver {
 	w.AddEvent(Z)
 	w.AddEvent(C)
 	w.AddEvent(Joystick)
+	w.AddEvent(Error)
 	return w
 }
 func (w *WiichuckDriver) Name() string                 { return w.name }
@@ -68,10 +72,12 @@ func (w *WiichuckDriver) Start() (errs []error) {
 				gobot.Publish(w.Event(Error), err)
 				continue
 			}
+			<-time.After(w.pauseTime)
 			if err := w.connection.I2cWrite(wiichuckAddress, []byte{0x00}); err != nil {
 				gobot.Publish(w.Event(Error), err)
 				continue
 			}
+			<-time.After(w.pauseTime)
 			newValue, err := w.connection.I2cRead(wiichuckAddress, 6)
 			if err != nil {
 				gobot.Publish(w.Event(Error), err)

sysfs/i2c_device.go

@@ -14,6 +14,11 @@ const (
 	I2C_SMBUS_WRITE          = 0
 	I2C_SMBUS_READ           = 1
 	I2C_SMBUS_I2C_BLOCK_DATA = 8
+
+	// Adapter functionality
+	I2C_FUNCS                       = 0x0705
+	I2C_FUNC_SMBUS_READ_BLOCK_DATA  = 0x01000000
+	I2C_FUNC_SMBUS_WRITE_BLOCK_DATA = 0x02000000
 )
 
 type i2cSmbusIoctlData struct {
@@ -29,7 +34,8 @@ type I2cDevice interface {
 }
 
 type i2cDevice struct {
-	file File
+	file  File
+	funcs uint64 // adapter functionality mask
 }
 
 // NewI2cDevice returns an io.ReadWriteCloser with the proper ioctrl given
@@ -40,12 +46,30 @@ func NewI2cDevice(location string, address int) (d *i2cDevice, err error) {
 	if d.file, err = OpenFile(location, os.O_RDWR, os.ModeExclusive); err != nil {
 		return
 	}
+	if err = d.queryFunctionality(); err != nil {
+		return
+	}
 
 	err = d.SetAddress(address)
 
 	return
 }
 
+func (d *i2cDevice) queryFunctionality() (err error) {
+	_, _, errno := Syscall(
+		syscall.SYS_IOCTL,
+		d.file.Fd(),
+		I2C_FUNCS,
+		uintptr(unsafe.Pointer(&d.funcs)),
+	)
+
+	if errno != 0 {
+		err = fmt.Errorf("Querying functionality failed with syscall.Errno %v", errno)
+	}
+	fmt.Printf("Functionality: 0x%x\n", d.funcs)
+	return
+}
+
 func (d *i2cDevice) SetAddress(address int) (err error) {
 	_, _, errno := Syscall(
 		syscall.SYS_IOCTL,
@@ -55,7 +79,7 @@ func (d *i2cDevice) SetAddress(address int) (err error) {
 	)
 
 	if errno != 0 {
-		err = fmt.Errorf("Failed with syscall.Errno %v", errno)
+		err = fmt.Errorf("Setting address failed with syscall.Errno %v", errno)
 	}
 
 	return
@@ -66,6 +90,11 @@ func (d *i2cDevice) Close() (err error) {
 }
 
 func (d *i2cDevice) Read(b []byte) (n int, err error) {
+	if d.funcs&I2C_FUNC_SMBUS_READ_BLOCK_DATA == 0 {
+		// Adapter doesn't support SMBus block read
+		return d.file.Read(b)
+	}
+
 	data := make([]byte, len(b)+1)
 	data[0] = byte(len(b))
 
@@ -83,7 +112,7 @@ func (d *i2cDevice) Read(b []byte) (n int, err error) {
 	)
 
 	if errno != 0 {
-		return n, fmt.Errorf("Failed with syscall.Errno %v", errno)
+		return n, fmt.Errorf("Read failed with syscall.Errno %v", errno)
 	}
 
 	copy(b, data[1:])
@@ -92,7 +121,8 @@ func (d *i2cDevice) Read(b []byte) (n int, err error) {
 }
 
 func (d *i2cDevice) Write(b []byte) (n int, err error) {
-	if len(b) <= 2 {
+	if d.funcs&I2C_FUNC_SMBUS_WRITE_BLOCK_DATA == 0 {
+		// Adapter doesn't support SMBus block write
 		return d.file.Write(b)
 	}
 
@@ -119,7 +149,7 @@ func (d *i2cDevice) Write(b []byte) (n int, err error) {
 	)
 
 	if errno != 0 {
-		err = fmt.Errorf("Failed with syscall.Errno %v", errno)
+		err = fmt.Errorf("Write failed with syscall.Errno %v", errno)
 	}
 
 	return len(b), err

sysfs/i2c_device_test.go

@@ -43,7 +43,7 @@ func TestNewI2cDevice(t *testing.T) {
 
 	n, err = i.Read(buf)
 
-	gobot.Assert(t, n, 4)
+	gobot.Assert(t, n, 3)
 	gobot.Assert(t, err, nil)
 
 }