From 07852b0cd66ba0b54abdbabb9b1eda902884c115 Mon Sep 17 00:00:00 2001
From: Joe Finney <joe@comp.lancs.ac.uk>
Date: Sat, 16 Jan 2016 17:07:20 +0000
Subject: [PATCH] microbit: Added support for BLE transmission power control

Added new method to MicroBitBLEManager to allow the radio transmission power
to be controlled. Provides a linear power level scale in the range 0..7.
---
 inc/MicroBitBLEManager.h                   |  9 +++++++++
 source/ble-services/MicroBitBLEManager.cpp | 23 ++++++++++++++++++++--
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/inc/MicroBitBLEManager.h b/inc/MicroBitBLEManager.h
index c4169e7..baab621 100644
--- a/inc/MicroBitBLEManager.h
+++ b/inc/MicroBitBLEManager.h
@@ -74,6 +74,15 @@ class MicroBitBLEManager
       */
     void init(ManagedString deviceName, ManagedString serialNumber);
 
+    /**
+     * Change the output power level of the transmitter to the given value.
+     *
+     * @param power a value in the range 0..7, where 0 is the lowest power and 7 is the highest. 
+     * @return MICROBIT_OK on success, or MICROBIT_INVALID_PARAMETER if the value is out of range.
+     *
+     */
+    int setTransmitPower(int power);
+    
     /**
      * Enter pairing mode. This is mode is called to initiate pairing, and to enable FOTA programming
      * of the micro:bit in cases where BLE is disabled during normal operation.
diff --git a/source/ble-services/MicroBitBLEManager.cpp b/source/ble-services/MicroBitBLEManager.cpp
index 9596cd8..8356994 100644
--- a/source/ble-services/MicroBitBLEManager.cpp
+++ b/source/ble-services/MicroBitBLEManager.cpp
@@ -25,6 +25,7 @@
 #define MICROBIT_BLE_REQUIRE_MITM		true
 
 #define MICROBIT_PAIRING_FADE_SPEED		4
+#define MICROBIT_BLE_POWER_LEVELS       8
 
 
 const char* MICROBIT_BLE_MANUFACTURER = "The Cast of W1A";
@@ -32,7 +33,7 @@ const char* MICROBIT_BLE_MODEL = "BBC micro:bit";
 const char* MICROBIT_BLE_HARDWARE_VERSION = "1.0";
 const char* MICROBIT_BLE_FIRMWARE_VERSION = MICROBIT_DAL_VERSION;
 const char* MICROBIT_BLE_SOFTWARE_VERSION = NULL;
-
+const int8_t MICROBIT_BLE_POWER_LEVEL[] = {-30, -20, -16, -12, -8, -4, 0, 4};
 
 /*
  * Many of the mbed interfaces we need to use only support callbacks to plain C functions, rather than C++ methods.
@@ -220,9 +221,27 @@ void MicroBitBLEManager::init(ManagedString deviceName, ManagedString serialNumb
     if (whitelist.size > 0)
 #endif        
         ble->startAdvertising();
-
 }
 
+/**
+ * Change the output power level of the transmitter to the given value.
+ *
+ * @param power a value in the range 0..7, where 0 is the lowest power and 7 is the highest. 
+ * @return MICROBIT_OK on success, or MICROBIT_INVALID_PARAMETER if the value is out of range.
+ *
+ */
+int MicroBitBLEManager::setTransmitPower(int power)
+{
+    if (power < 0 || power >= MICROBIT_BLE_POWER_LEVELS)
+        return MICROBIT_INVALID_PARAMETER;
+
+    if (ble->gap().setTxPower(MICROBIT_BLE_POWER_LEVEL[power]) != NRF_SUCCESS)
+        return MICROBIT_NOT_SUPPORTED;
+
+    return MICROBIT_OK;
+}
+
+
 /**
  * A request to pair has been received from a BLE device.
  * If we're in pairing mode, display the passkey to the user.