BattMon_Backend: add init and set_capacity methods

libraries/AP_BattMonitor/AP_BattMonitor.cpp

@@ -152,6 +152,11 @@ AP_BattMonitor::init()
 #endif
             _num_instances++;
         }
+
+        // call init function for each backend
+        if (drivers[instance] != NULL) {
+            drivers[instance]->init();
+        }
     }
 }
 

libraries/AP_BattMonitor/AP_BattMonitor_Backend.cpp

@@ -25,7 +25,8 @@
 */
 AP_BattMonitor_Backend::AP_BattMonitor_Backend(AP_BattMonitor &mon, uint8_t instance, AP_BattMonitor::BattMonitor_State &mon_state) :
         _mon(mon),
-        _state(mon_state)
+        _state(mon_state),
+        _instance(instance)
 {
 }
 
@@ -34,3 +35,9 @@ uint8_t AP_BattMonitor_Backend::capacity_remaining_pct() const
 {
     return (100.0f * (_mon._pack_capacity[_state.instance] - _state.current_total_mah) / _mon._pack_capacity[_state.instance]);
 }
+
+/// set capacity for this instance
+void AP_BattMonitor_Backend::set_capacity(uint32_t capacity)
+{
+    _mon._pack_capacity[_instance] = capacity;
+}

libraries/AP_BattMonitor/AP_BattMonitor_Backend.h

@@ -31,14 +31,21 @@ public:
     // override with a custom destructor if need be
     virtual ~AP_BattMonitor_Backend(void) {}
 
+    // initialise
+    virtual void init() {}
+
     // read the latest battery voltage
     virtual void read() = 0;
 
     /// capacity_remaining_pct - returns the % battery capacity remaining (0 ~ 100)
     uint8_t capacity_remaining_pct() const;
 
+    /// set capacity for this instance
+    void set_capacity(uint32_t capacity);
+
 protected:
     AP_BattMonitor                      &_mon;      // reference to front-end
     AP_BattMonitor::BattMonitor_State   &_state;    // reference to this instances state (held in the front-end)
+    uint8_t                              _instance; // this instance
 };
 #endif // __AP_BATTMONITOR_BACKEND_H__