AP_BattMonitor: add has_temperature method to Backend

libraries/AP_BattMonitor/AP_BattMonitor.cpp

@@ -488,12 +488,13 @@ const AP_BattMonitor::cells & AP_BattMonitor::get_cell_voltages(const uint8_t in
 // returns true if there is a temperature reading
 bool AP_BattMonitor::get_temperature(float &temperature, const uint8_t instance) const
 {
-    if (instance >= AP_BATT_MONITOR_MAX_INSTANCES) {
+    if (instance >= AP_BATT_MONITOR_MAX_INSTANCES || drivers[instance] == nullptr) {
         return false;
-    } else {
-        temperature = state[instance].temperature;
-        return (AP_HAL::millis() - state[instance].temperature_time) <= AP_BATT_MONITOR_TIMEOUT;
-    }
+    } 
+    
+    temperature = state[instance].temperature;
+
+    return drivers[instance]->has_temperature();
 }
 
 // return true if cycle count can be provided and fills in cycles argument

libraries/AP_BattMonitor/AP_BattMonitor_Backend.h

@@ -43,6 +43,9 @@ public:
     // returns true if battery monitor provides individual cell voltages
     virtual bool has_cell_voltages() const { return false; }
 
+    // returns true if battery monitor provides temperature
+    virtual bool has_temperature() const { return false; }
+
     /// capacity_remaining_pct - returns the % battery capacity remaining (0 ~ 100)
     uint8_t capacity_remaining_pct() const;
 

libraries/AP_BattMonitor/AP_BattMonitor_SMBus.cpp

@@ -84,10 +84,14 @@ bool AP_BattMonitor_SMBus::read_temp(void)
 {
     uint16_t data;
     if (read_word(BATTMONITOR_SMBUS_TEMP, data)) {
+        _has_temperature = (AP_HAL::millis() - _state.temperature_time) <= AP_BATT_MONITOR_TIMEOUT;
+
         _state.temperature_time = AP_HAL::millis();
         _state.temperature = ((float)(data - 2731)) * 0.1f;
         return true;
     }
+    
+    _has_temperature = false;
 
     return false;
 }

libraries/AP_BattMonitor/AP_BattMonitor_SMBus.h

@@ -41,6 +41,8 @@ public:
 
     bool has_cell_voltages() const override { return _has_cell_voltages; }
 
+    bool has_temperature() const override { return _has_temperature; }
+
     // all smart batteries are expected to provide current
     bool has_current() const override { return true; }
 
@@ -95,6 +97,7 @@ protected:
     bool _has_cell_voltages;        // smbus backends flag this as true once they have received a valid cell voltage report
     uint16_t _cycle_count = 0;      // number of cycles the battery has experienced. An amount of discharge approximately equal to the value of DesignCapacity.
     bool _has_cycle_count;          // true if cycle count has been retrieved from the battery
+    bool _has_temperature;
 
     virtual void timer(void) = 0;   // timer function to read from the battery