AP_BattMonitor: added 2nd battery voltage monitoring

libraries/AP_BattMonitor/AP_BattMonitor.cpp

@@ -13,7 +13,7 @@ const AP_Param::GroupInfo AP_BattMonitor::var_info[] PROGMEM = {
 
     // @Param: VOLT_PIN
     // @DisplayName: Battery Voltage sensing pin
-    // @Description: Setting this to 0 ~ 13 will enable battery current sensing on pins A0 ~ A13. For the 3DR power brick on APM2.5 it should be set to 13. On the PX4 it should be set to 100. On the Pixhawk powered from the PM connector it should be set to 2.
+    // @Description: Setting this to 0 ~ 13 will enable battery voltage sensing on pins A0 ~ A13. For the 3DR power brick on APM2.5 it should be set to 13. On the PX4 it should be set to 100. On the Pixhawk powered from the PM connector it should be set to 2.
     // @Values: -1:Disabled, 0:A0, 1:A1, 2:Pixhawk, 13:A13, 100:PX4
     // @User: Standard
     AP_GROUPINFO("VOLT_PIN", 1, AP_BattMonitor, _volt_pin, AP_BATT_VOLT_PIN),
@@ -53,6 +53,18 @@ const AP_Param::GroupInfo AP_BattMonitor::var_info[] PROGMEM = {
     // @User: Standard
     AP_GROUPINFO("CAPACITY", 6, AP_BattMonitor, _pack_capacity, AP_BATT_CAPACITY_DEFAULT),
 
+    // @Param: VOLT2_PIN
+    // @DisplayName: 2nd Battery Voltage sensing pin
+    // @Description: This sets the pin for sensing the voltage on a 2nd battery. Set to -1 to disable sensing of a second battery
+    // @User: Standard
+    AP_GROUPINFO("VOLT2_PIN", 7, AP_BattMonitor, _volt2_pin, -1),
+
+    // @Param: VOLT2_MULT
+    // @DisplayName: 2nd battery voltage multiplier
+    // @Description: Used to convert the voltage of the VOLT2_PIN to the actual battery's voltage (pin_voltage * VOLT_MULT).
+    // @User: Advanced
+    AP_GROUPINFO("VOLT2_MULT", 8, AP_BattMonitor, _volt2_multiplier, 1),
+
     AP_GROUPEND
 };
 
@@ -62,6 +74,7 @@ const AP_Param::GroupInfo AP_BattMonitor::var_info[] PROGMEM = {
 //
 AP_BattMonitor::AP_BattMonitor(void) :
     _voltage(0),
+    _voltage2(0),
     _current_amps(0),
     _current_total_mah(0),
     _last_time_micros(0)
@@ -75,6 +88,11 @@ AP_BattMonitor::init()
 {
     _volt_pin_analog_source = hal.analogin->channel(_volt_pin);
     _curr_pin_analog_source = hal.analogin->channel(_curr_pin);
+    if (_volt2_pin != -1) {
+        _volt2_pin_analog_source = hal.analogin->channel(_volt2_pin);
+    } else {
+        _volt2_pin_analog_source = NULL;
+    }
 }
 
 // read - read the voltage and current
@@ -90,6 +108,9 @@ AP_BattMonitor::read()
         // this copes with changing the pin at runtime
         _volt_pin_analog_source->set_pin(_volt_pin);
         _voltage = _volt_pin_analog_source->voltage_average() * _volt_multiplier;
+        if (_volt2_pin_analog_source != NULL) {
+            _voltage2 = _volt2_pin_analog_source->voltage_average() * _volt2_multiplier;
+        }
     }
 
     // read current
@@ -145,3 +166,13 @@ bool AP_BattMonitor::exhausted(float low_voltage, float min_capacity_mah)
     // if we've gotten this far battery is ok
     return false;
 }
+
+/// 2nd Battery voltage, if available. return false otherwise
+bool AP_BattMonitor::voltage2(float &v) const
+{
+    if (_volt2_pin_analog_source != NULL) {
+        v = _voltage2;
+        return true;
+    }
+    return false;
+}

libraries/AP_BattMonitor/AP_BattMonitor.h

@@ -116,9 +116,12 @@ public:
     /// monitoring - returns whether we are monitoring voltage only or voltage and current
     void set_monitoring(uint8_t mon) { _monitoring.set(mon); }
 
-    /// Battery voltage.  Initialized to 99 to prevent low voltage events at startup
+    /// Battery voltage.  Initialized to 0
     float voltage() const { return _voltage; }
 
+    /// 2nd Battery voltage, if available. return false otherwise
+    bool voltage2(float &voltage) const;
+
     /// Battery pack instantaneous currrent draw in amperes
     float current_amps() const { return _current_amps; }
 
@@ -144,8 +147,13 @@ protected:
     AP_Float    _curr_amp_offset;           /// offset voltage that is subtracted from current pin before conversion to amps
     AP_Int32    _pack_capacity;             /// battery pack capacity less reserve in mAh
 
+    // 2nd battery monitoring
+    AP_Int8     _volt2_pin;                 /// board pin used to measure 2nd battery voltage
+    AP_Float    _volt2_multiplier;          /// voltage on volt2 pin multiplier
+
     /// internal variables
     float       _voltage;                   /// last read voltage
+    float       _voltage2;                  /// last read voltage 2nd battery
     float       _current_amps;              /// last read current drawn
     float       _current_total_mah;         /// total current drawn since startup (Amp-hours)
     uint32_t    _last_time_micros;          /// time when current was last read
@@ -153,6 +161,6 @@ protected:
 
     AP_HAL::AnalogSource *_volt_pin_analog_source;
     AP_HAL::AnalogSource *_curr_pin_analog_source;
-
+    AP_HAL::AnalogSource *_volt2_pin_analog_source;
 };
 #endif  // AP_BATTMONITOR_H