GCS_MAVLink: send_battery_status sends min of cell 10 11 and 12

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -199,19 +199,29 @@ void GCS_MAVLINK::send_battery_status(const uint8_t instance) const
     float temp;
     bool got_temperature = battery.get_temperature(temp, instance);
 
-    // ensure we always send a voltage estimate to the GCS, because not all battery monitors monitor individual cells
-    // as a work around for this we create a set of fake cells to be used if the backend doesn't provide direct monitoring
-    // the GCS can then recover the pack voltage by summing all non ignored cell values. Because this is looped we can
-    // report a pack up to 655.34 V with this method
-    AP_BattMonitor::cells fake_cells;
-    if (!battery.has_cell_voltages(instance)) {
+    // prepare array of individual cell voltage
+    uint16_t cell_volts[MAVLINK_MSG_BATTERY_STATUS_FIELD_VOLTAGES_LEN];
+    if (battery.has_cell_voltages(instance)) {
+        const AP_BattMonitor::cells& batt_cells = battery.get_cell_voltages(instance);
+        for (uint8_t i = 0; i < ARRAY_SIZE(batt_cells.cells); i++) {
+            if (i < MAVLINK_MSG_BATTERY_STATUS_FIELD_VOLTAGES_LEN) {
+                cell_volts[i] = batt_cells.cells[i];
+            } else {
+                // 10th cell reports the lowest voltage of the last 3 cells
+                cell_volts[MAVLINK_MSG_BATTERY_STATUS_FIELD_VOLTAGES_LEN-1] = MIN(cell_volts[MAVLINK_MSG_BATTERY_STATUS_FIELD_VOLTAGES_LEN-1], batt_cells.cells[i]);
+            }
+        }
+    } else {
+        // for battery monitors that cannot provide voltages for individual cells the battery's total voltage is put into the first cell
+        // if the total voltage cannot fit into a single field, the remainder into subsequent fields.
+        // the GCS can then recover the pack voltage by summing all non ignored cell values an we can report a pack up to 655.34 V
         float voltage = battery.voltage(instance) * 1e3f;
         for (uint8_t i = 0; i < MAVLINK_MSG_BATTERY_STATUS_FIELD_VOLTAGES_LEN; i++) {
           if (voltage < 0.001f) {
               // too small to send to the GCS, set it to the no cell value
-              fake_cells.cells[i] = UINT16_MAX;
+              cell_volts[i] = UINT16_MAX;
           } else {
-              fake_cells.cells[i] = MIN(voltage, 65534.0f); // Can't send more then UINT16_MAX - 1 in a cell
+              cell_volts[i] = MIN(voltage, 65534.0f); // Can't send more then UINT16_MAX - 1 in a cell
               voltage -= 65534.0f;
           }
         }
@@ -236,7 +246,7 @@ void GCS_MAVLINK::send_battery_status(const uint8_t instance) const
                                     MAV_BATTERY_FUNCTION_UNKNOWN, // function
                                     MAV_BATTERY_TYPE_UNKNOWN, // type
                                     got_temperature ? ((int16_t) (temp * 100)) : INT16_MAX, // temperature. INT16_MAX if unknown
-                                    battery.has_cell_voltages(instance) ? battery.get_cell_voltages(instance).cells : fake_cells.cells, // cell voltages
+                                    cell_volts, // cell voltages
                                     current,      // current in centiampere
                                     consumed_mah, // total consumed current in milliampere.hour
                                     consumed_wh,  // consumed energy in hJ (hecto-Joules)