microbit: Added first draft of BLE Accelerometer service

n.b. this code is as yet untested.

inc/MicroBitAccelerometerService.h

@@ -0,0 +1,48 @@
+#ifndef MICROBIT_ACCELEROMETER_SERVICE_H
+#define MICROBIT_ACCELEROMETER_SERVICE_H
+
+#include "MicroBit.h"
+
+// UUIDs for our service and characteristics
+extern const uint8_t  MicroBitAccelerometerServiceUUID[];
+extern const uint8_t  MicroBitAccelerometerServiceDataUUID[];
+extern const uint8_t  MicroBitAccelerometerServicePeriodUUID[];
+
+
+/**
+  * Class definition for a MicroBit BLE Accelerometer Service.
+  * Provides access to live accelerometer data via BLE, and provides basic configuration options.
+  */
+class MicroBitAccelerometerService
+{                                    
+    public:
+    
+    /**
+      * Constructor. 
+      * Create a representation of the AccelerometerService
+      * @param _ble The instance of a BLE device that we're running on.
+      */
+    MicroBitAccelerometerService(BLEDevice &_ble);  
+    
+    /**
+      * Callback. Invoked when any of our attributes are written via BLE.
+      */
+    void onDataWritten(const GattWriteCallbackParams *params);
+
+    private:
+
+    // Bluetooth stack we're running on.
+    BLEDevice           &ble;
+
+    // memory for our 8 bit control characteristics.
+    uint16_t            accelerometerDataCharacteristicBuffer[3];
+    uint8_t             accelerometerPeriodCharacteristicBuffer;
+
+    // Handles to access each characteristic when they are held by Soft Device.
+    GattAttribute::Handle_t accelerometerDataCharacteristicHandle;
+    GattAttribute::Handle_t accelerometerPeriodCharacteristicHandle;
+};
+
+
+#endif
+

source/CMakeLists.txt

@@ -29,6 +29,7 @@ set(YOTTA_AUTO_MICROBIT-DAL_CPP_FILES
     "ble-services/MicroBitDFUService.cpp"
     "ble-services/MicroBitEventService.cpp"
     "ble-services/MicroBitLEDService.cpp"
+    "ble-services/MicroBitAccelerometerService.cpp"
 )
 
 if (YOTTA_CFG_MICROBIT_CONFIGFILE)

source/ble-services/MicroBitAccelerometerService.cpp

@@ -0,0 +1,73 @@
+/**
+  * Class definition for the custom MicroBit Accelerometer Service.
+  * Provides a BLE service to remotely read the state of the accelerometer, and configure its behaviour.
+  */
+  
+#include "MicroBit.h"
+#include "ble/UUID.h"
+
+#include "MicroBitAccelerometerService.h"
+
+/**
+  * Constructor. 
+  * Create a representation of the AccelerometerService
+  * @param _ble The instance of a BLE device that we're running on.
+  */
+MicroBitAccelerometerService::MicroBitAccelerometerService(BLEDevice &_ble) : 
+        ble(_ble) 
+{
+    // Create the data structures that represent each of our characteristics in Soft Device.
+    GattCharacteristic  accelerometerDataCharacteristic(MicroBitAccelerometerServiceDataUUID, (uint8_t *)accelerometerDataCharacteristicBuffer, 0, 
+    sizeof(accelerometerDataCharacteristicBuffer), GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY);
+
+    GattCharacteristic  accelerometerPeriodCharacteristic(MicroBitAccelerometerServicePeriodUUID, (uint8_t *)accelerometerPeriodCharacteristicBuffer, 0, 
+    sizeof(accelerometerPeriodCharacteristicBuffer), 
+    GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE_WITHOUT_RESPONSE);
+
+    // Initialise our characteristic values.
+    accelerometerDataCharacteristicBuffer[0] = 0;
+    accelerometerDataCharacteristicBuffer[1] = 0;
+    accelerometerDataCharacteristicBuffer[2] = 0;
+    accelerometerPeriodCharacteristicBuffer = 0;
+    
+    GattCharacteristic *characteristics[] = {&accelerometerDataCharacteristic, &accelerometerPeriodCharacteristic};
+    GattService         service(MicroBitAccelerometerServiceUUID, characteristics, sizeof(characteristics) / sizeof(GattCharacteristic *));
+
+    ble.addService(service);
+
+    accelerometerDataCharacteristicHandle = accelerometerDataCharacteristic.getValueHandle();
+    accelerometerPeriodCharacteristicHandle = accelerometerPeriodCharacteristic.getValueHandle();
+
+    ble.updateCharacteristicValue(accelerometerDataCharacteristicHandle, (const uint8_t *)&accelerometerDataCharacteristicBuffer, sizeof(accelerometerDataCharacteristicBuffer));
+    ble.updateCharacteristicValue(accelerometerPeriodCharacteristicHandle, (const uint8_t *)&accelerometerPeriodCharacteristicBuffer, sizeof(accelerometerPeriodCharacteristicBuffer));
+
+    ble.onDataWritten(this, &MicroBitAccelerometerService::onDataWritten);
+}
+
+
+/**
+  * Callback. Invoked when any of our attributes are written via BLE.
+  */
+void MicroBitAccelerometerService::onDataWritten(const GattWriteCallbackParams *params)
+{   
+    if (params->handle == accelerometerPeriodCharacteristicHandle && params->len >= sizeof(accelerometerPeriodCharacteristicBuffer))
+    {
+        accelerometerPeriodCharacteristicBuffer = *((uint8_t *)params->data);
+        uBit.accelerometer.setPeriod(accelerometerPeriodCharacteristicBuffer);
+    }
+}
+
+
+const uint8_t  MicroBitAccelerometerServiceUUID[] = {
+    0xe9,0x5d,0x07,0x53,0x25,0x1d,0x47,0x0a,0xa0,0x62,0xfa,0x19,0x22,0xdf,0xa9,0xa8
+};
+
+const uint8_t  MicroBitAccelerometerServiceDataUUID[] = {
+    0xe9,0x5d,0xca,0x4b,0x25,0x1d,0x47,0x0a,0xa0,0x62,0xfa,0x19,0x22,0xdf,0xa9,0xa8
+};
+
+const uint8_t  MicroBitAccelerometerServicePeriodUUID[] = {
+    0xe9,0x5d,0xfb,0x24,0x25,0x1d,0x47,0x0a,0xa0,0x62,0xfa,0x19,0x22,0xdf,0xa9,0xa8
+};
+
+