microbit: First draft of Magnetometer BLE service

inc/MicroBitMagnetometerService.h

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+#ifndef MICROBIT_MAGNETOMETER_SERVICE_H
+#define MICROBIT_MAGNETOMETER_SERVICE_H
+
+#include "MicroBit.h"
+
+// UUIDs for our service and characteristics
+extern const uint8_t  MicroBitMagnetometerServiceUUID[];
+extern const uint8_t  MicroBitMagnetometerServiceDataUUID[];
+extern const uint8_t  MicroBitMagnetometerServiceBearingUUID[];
+extern const uint8_t  MicroBitMagnetometerServicePeriodUUID[];
+
+
+/**
+  * Class definition for a MicroBit BLE Magnetometer Service.
+  * Provides access to live magnetometer data via BLE, and provides basic configuration options.
+  */
+class MicroBitMagnetometerService
+{                                    
+    public:
+    
+    /**
+      * Constructor. 
+      * Create a representation of the MagnetometerService
+      * @param _ble The instance of a BLE device that we're running on.
+      */
+    MicroBitMagnetometerService(BLEDevice &_ble);  
+    
+
+    private:
+
+    /**
+      * Callback. Invoked when any of our attributes are written via BLE.
+      */
+    void onDataWritten(const GattWriteCallbackParams *params);
+
+    /**
+     * Magnetometer update callback
+     */
+    void magnetometerUpdate(MicroBitEvent e);
+
+    // Bluetooth stack we're running on.
+    BLEDevice           &ble;
+
+    // memory for our 8 bit control characteristics.
+    uint16_t            magnetometerDataCharacteristicBuffer[3];
+    uint16_t            magnetometerBearingCharacteristicBuffer;
+    uint16_t            magnetometerPeriodCharacteristicBuffer;
+
+    // Handles to access each characteristic when they are held by Soft Device.
+    GattAttribute::Handle_t magnetometerDataCharacteristicHandle;
+    GattAttribute::Handle_t magnetometerBearingCharacteristicHandle;
+    GattAttribute::Handle_t magnetometerPeriodCharacteristicHandle;
+};
+
+#endif
+

source/ble-services/MicroBitMagnetometerService.cpp

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+/**
+  * Class definition for the custom MicroBit Magnetometer Service.
+  * Provides a BLE service to remotely read the state of the magnetometer, and configure its behaviour.
+  */
+  
+#include "MicroBit.h"
+#include "ble/UUID.h"
+
+#include "MicroBitMagnetometerService.h"
+
+/**
+  * Constructor. 
+  * Create a representation of the MagnetometerService
+  * @param _ble The instance of a BLE device that we're running on.
+  */
+MicroBitMagnetometerService::MicroBitMagnetometerService(BLEDevice &_ble) : 
+        ble(_ble) 
+{
+    // Create the data structures that represent each of our characteristics in Soft Device.
+    GattCharacteristic  magnetometerDataCharacteristic(MicroBitMagnetometerServiceDataUUID, (uint8_t *)magnetometerDataCharacteristicBuffer, 0, 
+    sizeof(magnetometerDataCharacteristicBuffer), GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY);
+
+    GattCharacteristic  magnetometerBearingCharacteristic(MicroBitMagnetometerServiceBearingUUID, (uint8_t *)magnetometerBearingCharacteristicBuffer, 0, 
+    sizeof(magnetometerBearingCharacteristicBuffer), GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY);
+
+    GattCharacteristic  magnetometerPeriodCharacteristic(MicroBitMagnetometerServicePeriodUUID, (uint8_t *)magnetometerPeriodCharacteristicBuffer, 0, 
+    sizeof(magnetometerPeriodCharacteristicBuffer), 
+    GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE_WITHOUT_RESPONSE);
+
+    // Initialise our characteristic values.
+    magnetometerDataCharacteristicBuffer[0] = 0;
+    magnetometerDataCharacteristicBuffer[1] = 0;
+    magnetometerDataCharacteristicBuffer[2] = 0;
+    magnetometerBearingCharacteristicBuffer = 0;
+    magnetometerPeriodCharacteristicBuffer = 0;
+    
+    GattCharacteristic *characteristics[] = {&magnetometerDataCharacteristic, &magnetometerBearingCharacteristic, &magnetometerPeriodCharacteristic};
+    GattService         service(MicroBitMagnetometerServiceUUID, characteristics, sizeof(characteristics) / sizeof(GattCharacteristic *));
+
+    ble.addService(service);
+
+    magnetometerDataCharacteristicHandle = magnetometerDataCharacteristic.getValueHandle();
+    magnetometerBearingCharacteristicHandle = magnetometerBearingCharacteristic.getValueHandle();
+    magnetometerPeriodCharacteristicHandle = magnetometerPeriodCharacteristic.getValueHandle();
+
+    ble.updateCharacteristicValue(magnetometerDataCharacteristicHandle, (const uint8_t *)&magnetometerDataCharacteristicBuffer, sizeof(magnetometerDataCharacteristicBuffer));
+    ble.updateCharacteristicValue(magnetometerBearingCharacteristicHandle, (const uint8_t *)&magnetometerDataCharacteristicBuffer, sizeof(magnetometerDataCharacteristicBuffer));
+    ble.updateCharacteristicValue(magnetometerPeriodCharacteristicHandle, (const uint8_t *)&magnetometerPeriodCharacteristicBuffer, sizeof(magnetometerPeriodCharacteristicBuffer));
+
+    ble.onDataWritten(this, &MicroBitMagnetometerService::onDataWritten);
+    uBit.MessageBus.listen(MICROBIT_ID_COMPASS, MICROBIT_COMPASS_EVT_DATA_UPDATE, this, &MicroBitMagnetometerService::magnetometerUpdate, MESSAGE_BUS_LISTENER_NONBLOCKING | MESSAGE_BUS_LISTENER_URGENT);
+}
+
+/**
+  * Callback. Invoked when any of our attributes are written via BLE.
+  */
+void MicroBitMagnetometerService::onDataWritten(const GattWriteCallbackParams *params)
+{   
+    if (params->handle == magnetometerPeriodCharacteristicHandle && params->len >= sizeof(magnetometerPeriodCharacteristicBuffer))
+    {
+        magnetometerPeriodCharacteristicBuffer = *((uint8_t *)params->data);
+        uBit.compass.setPeriod(magnetometerPeriodCharacteristicBuffer);
+    }
+}
+
+/**
+  * Magnetometer update callback
+  */
+void MicroBitMagnetometerService::magnetometerUpdate(MicroBitEvent e)
+{
+    magnetometerDataCharacteristicBuffer[0] = uBit.compass.getX();
+    magnetometerDataCharacteristicBuffer[1] = uBit.compass.getY();
+    magnetometerDataCharacteristicBuffer[2] = uBit.compass.getZ();
+    magnetometerBearingCharacteristicBuffer = (uint16_t) uBit.compass.bearing();
+
+    ble.gattServer().notify(magnetometerDataCharacteristicHandle,(uint8_t *)magnetometerDataCharacteristicBuffer, sizeof(magnetometerDataCharacteristicBuffer));
+    ble.gattServer().notify(magnetometerDataCharacteristicHandle,(uint8_t *)magnetometerBearingCharacteristicBuffer, sizeof(magnetometerDataCharacteristicBuffer));
+}
+
+const uint8_t  MicroBitMagnetometerServiceUUID[] = {
+    0xe9,0x5d,0xf2,0xd8,0x25,0x1d,0x47,0x0a,0xa0,0x62,0xfa,0x19,0x22,0xdf,0xa9,0xa8
+};
+
+const uint8_t  MicroBitMagnetometerServiceDataUUID[] = {
+    0xe9,0x5d,0xfb,0x11,0x25,0x1d,0x47,0x0a,0xa0,0x62,0xfa,0x19,0x22,0xdf,0xa9,0xa8
+};
+
+
+const uint8_t  MicroBitMagnetometerServicePeriodUUID[] = {
+    0xe9,0x5d,0x38,0x6c,0x25,0x1d,0x47,0x0a,0xa0,0x62,0xfa,0x19,0x22,0xdf,0xa9,0xa8
+};
+
+// TODO: Need an assigned UUID from martin here..
+const uint8_t  MicroBitMagnetometerServiceBearingUUID[] = {
+    0xe9,0x5d,0xde,0xad,0x25,0x1d,0x47,0x0a,0xa0,0x62,0xfa,0x19,0x22,0xdf,0xa9,0xa8
+};
+
+