microbit: add magnetometer driver

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

examples/microbit_magnetometer.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"gobot.io/x/gobot"
+	"gobot.io/x/gobot/platforms/ble"
+	"gobot.io/x/gobot/platforms/microbit"
+)
+
+func main() {
+	bleAdaptor := ble.NewClientAdaptor(os.Args[1])
+	ubit := microbit.NewMagnetometerDriver(bleAdaptor)
+
+	work := func() {
+		ubit.On(microbit.Magnetometer, func(data interface{}) {
+			fmt.Println("Magnetometer", data)
+		})
+	}
+
+	robot := gobot.NewRobot("magnetoBot",
+		[]gobot.Connection{bleAdaptor},
+		[]gobot.Device{ubit},
+		work,
+	)
+
+	robot.Start()
+}

platforms/microbit/README.md

@@ -7,6 +7,12 @@ The [Microbit](http://microbit.org/) is a tiny computer with built-in Bluetooth
 go get -d -u gobot.io/x/gobot/... && go install gobot.io/x/gobot/platforms/microbit
 ```
 
+You must install the Microbit firmware from [@sandeepmistry] located at  [https://github.com/sandeepmistry/node-bbc-microbit](https://github.com/sandeepmistry/node-bbc-microbit) to use the Microbit with Gobot. This firmware is based on the micro:bit template, but with a few changes.
+
+You can either use the [Gort](https://gort.io) command line tool's `gort microbit` commands, or follow the firmware installation instructions at [https://github.com/sandeepmistry/node-bbc-microbit#flashing-microbit-firmware](https://github.com/sandeepmistry/node-bbc-microbit#flashing-microbit-firmware).
+
+The source code for the firmware is located at [https://github.com/sandeepmistry/node-bbc-microbit/files/546610/node-bbc-microbit_zip_nrf51_microbit.zip](https://github.com/sandeepmistry/node-bbc-microbit/files/546610/node-bbc-microbit_zip_nrf51_microbit.zip) however you do not need this source code to install the firmware using the installation instructions.
+
 ## How to Use
 
 The Gobot platform for the Microbit includes several different drivers, each one corresponding to a different capability:

platforms/microbit/accelerometer_driver.go

@@ -67,7 +67,7 @@ func (b *AccelerometerDriver) adaptor() *ble.ClientAdaptor {
 
 // Start tells driver to get ready to do work
 func (b *AccelerometerDriver) Start() (err error) {
-	// subscribe to button A notifications
+	// subscribe to accelerometer notifications
 	b.adaptor().Subscribe(accelerometerCharacteristic, func(data []byte, e error) {
 		a := &RawAccelerometerData{X: 0, Y: 0, Z: 0}
 
@@ -76,7 +76,8 @@ func (b *AccelerometerDriver) Start() (err error) {
 		binary.Read(buf, binary.LittleEndian, &a.Y)
 		binary.Read(buf, binary.LittleEndian, &a.Z)
 
-		result := &AccelerometerData{X: float32(a.X) / 1000.0,
+		result := &AccelerometerData{
+			X: float32(a.X) / 1000.0,
 			Y: float32(a.Y) / 1000.0,
 			Z: float32(a.Z) / 1000.0}
 

platforms/microbit/magnetometer_driver.go

@@ -0,0 +1,93 @@
+package microbit
+
+import (
+	"bytes"
+	"encoding/binary"
+
+	"gobot.io/x/gobot"
+	"gobot.io/x/gobot/platforms/ble"
+)
+
+// MagnetometerDriver is the Gobot driver for the Microbit's built-in magnetometer
+type MagnetometerDriver struct {
+	name       string
+	connection gobot.Connection
+	gobot.Eventer
+}
+
+type RawMagnetometerData struct {
+	X int16
+	Y int16
+	Z int16
+}
+
+type MagnetometerData struct {
+	X float32
+	Y float32
+	Z float32
+}
+
+const (
+	// BLE services
+	magnetometerService = "e95df2d8251d470aa062fa1922dfa9a8"
+
+	// BLE characteristics
+	magnetometerCharacteristic = "e95dfb11251d470aa062fa1922dfa9a8"
+
+	// Magnetometer event
+	Magnetometer = "magnetometer"
+)
+
+// NewMagnetometerDriver creates a Microbit MagnetometerDriver
+func NewMagnetometerDriver(a *ble.ClientAdaptor) *MagnetometerDriver {
+	n := &MagnetometerDriver{
+		name:       gobot.DefaultName("Microbit Magnetometer"),
+		connection: a,
+		Eventer:    gobot.NewEventer(),
+	}
+
+	n.AddEvent(Magnetometer)
+
+	return n
+}
+
+// Connection returns the BLE connection
+func (b *MagnetometerDriver) Connection() gobot.Connection { return b.connection }
+
+// Name returns the Driver Name
+func (b *MagnetometerDriver) Name() string { return b.name }
+
+// SetName sets the Driver Name
+func (b *MagnetometerDriver) SetName(n string) { b.name = n }
+
+// adaptor returns BLE adaptor
+func (b *MagnetometerDriver) adaptor() *ble.ClientAdaptor {
+	return b.Connection().(*ble.ClientAdaptor)
+}
+
+// Start tells driver to get ready to do work
+func (b *MagnetometerDriver) Start() (err error) {
+	// subscribe to magnetometer notifications
+	b.adaptor().Subscribe(magnetometerCharacteristic, func(data []byte, e error) {
+		a := &RawMagnetometerData{X: 0, Y: 0, Z: 0}
+
+		buf := bytes.NewBuffer(data)
+		binary.Read(buf, binary.LittleEndian, &a.X)
+		binary.Read(buf, binary.LittleEndian, &a.Y)
+		binary.Read(buf, binary.LittleEndian, &a.Z)
+
+		result := &MagnetometerData{
+			X: float32(a.X) / 1000.0,
+			Y: float32(a.Y) / 1000.0,
+			Z: float32(a.Z) / 1000.0}
+
+		b.Publish(b.Event(Magnetometer), result)
+	})
+
+	return
+}
+
+// Halt stops LED driver (void)
+func (b *MagnetometerDriver) Halt() (err error) {
+	return
+}

platforms/microbit/magnetometer_driver_test.go

@@ -0,0 +1,23 @@
+package microbit
+
+import (
+	"strings"
+	"testing"
+
+	"gobot.io/x/gobot"
+	"gobot.io/x/gobot/gobottest"
+
+	"gobot.io/x/gobot/platforms/ble"
+)
+
+var _ gobot.Driver = (*MagnetometerDriver)(nil)
+
+func initTestMagnetometerDriver() *MagnetometerDriver {
+	d := NewMagnetometerDriver(ble.NewClientAdaptor("D7:99:5A:26:EC:38"))
+	return d
+}
+
+func TestMagnetometerDriver(t *testing.T) {
+	d := initTestMagnetometerDriver()
+	gobottest.Assert(t, strings.HasPrefix(d.Name(), "Microbit Magnetometer"), true)
+}