i2c: refactor all i2c drivers to use Address property of Driver. Allows variations to override the default address as discussed in #14 (#30)

Signed-off-by: Ron Evans <ron@hybridgroup.com>

bh1750/bh1750.go

@@ -16,8 +16,9 @@ type SamplingMode byte
 
 // Device wraps an I2C connection to a bh1750 device.
 type Device struct {
-	bus  machine.I2C
-	mode SamplingMode
+	bus     machine.I2C
+	Address uint16
+	mode    SamplingMode
 }
 
 // New creates a new bh1750 connection. The I2C bus must already be
@@ -26,14 +27,15 @@ type Device struct {
 // This function only creates the Device object, it does not touch the device.
 func New(bus machine.I2C) Device {
 	return Device{
-		bus:  bus,
-		mode: CONTINUOUS_HIGH_RES_MODE,
+		bus:     bus,
+		Address: Address,
+		mode:    CONTINUOUS_HIGH_RES_MODE,
 	}
 }
 
 // Configure sets up the device for communication
 func (d *Device) Configure() {
-	d.bus.Tx(Address, []byte{POWER_ON}, nil)
+	d.bus.Tx(d.Address, []byte{POWER_ON}, nil)
 	d.SetMode(d.mode)
 }
 
@@ -41,7 +43,7 @@ func (d *Device) Configure() {
 func (d *Device) RawSensorData() uint16 {
 
 	buf := []byte{1, 0}
-	d.bus.Tx(Address, nil, buf)
+	d.bus.Tx(d.Address, nil, buf)
 	return (uint16(buf[0]) << 8) | uint16(buf[1])
 }
 
@@ -65,6 +67,6 @@ func (d *Device) Illuminance() int32 {
 // SetMode changes the reading mode for the sensor
 func (d *Device) SetMode(mode SamplingMode) {
 	d.mode = mode
-	d.bus.Tx(Address, []byte{byte(d.mode)}, nil)
+	d.bus.Tx(d.Address, []byte{byte(d.mode)}, nil)
 	time.Sleep(10 * time.Millisecond)
 }