OP-1299 Added autodetect battery cell number before arming. Tested for LiPo from 2S to 6S. Over 6S counting is not possible for LiPo. Should work for LiCo too. LiFePo works only for 1S or 2S. I was not able to find values for LiFeSO4. FlightBatteryState has now two new fields: NbCells and NbCellsAutodetected, which register the autodetection. FlightBatteryState.NbCells should be used instead of FlightBatterySettings.NbCells now, when the number of cells in needed. FlightBatterySettings.NbCells is used by the user to prescribe a cell number or if equal to zero to ask for autodetection.

flight/modules/Battery/battery.c

@@ -47,6 +47,7 @@
 
 #include "openpilot.h"
 
+#include "flightstatus.h"
 #include "flightbatterystate.h"
 #include "flightbatterysettings.h"
 #include "hwsettings.h"
@@ -69,6 +70,7 @@ static int8_t currentADCPin = -1; // ADC pin for current
 
 // Private functions
 static void onTimer(UAVObjEvent *ev);
+static int8_t GetNbCells(const FlightBatterySettingsData *batterySettings, FlightBatteryStateData *flightBatteryData);
 
 /**
  * Initialise the module, called on startup
@@ -113,6 +115,8 @@ int32_t BatteryInitialize(void)
         FlightBatteryStateInitialize();
         FlightBatterySettingsInitialize();
 
+        // FlightBatterySettingsConnectCallback(FlightBatterySettingsUpdatedCb);
+
         static UAVObjEvent ev;
 
         memset(&ev, 0, sizeof(UAVObjEvent));
@@ -125,10 +129,11 @@ int32_t BatteryInitialize(void)
 MODULE_INITCALL(BatteryInitialize, 0);
 static void onTimer(__attribute__((unused)) UAVObjEvent *ev)
 {
-    static FlightBatteryStateData flightBatteryData;
     static FlightBatterySettingsData batterySettings;
+    static FlightBatteryStateData flightBatteryData;
 
     FlightBatterySettingsGet(&batterySettings);
+    FlightBatteryStateGet(&flightBatteryData);
 
     const float dT = SAMPLE_PERIOD_MS / 1000.0f;
     float energyRemaining;
@@ -140,7 +145,11 @@ static void onTimer(__attribute__((unused)) UAVObjEvent *ev)
         flightBatteryData.Voltage = 0; // Dummy placeholder value. This is in case we get another source of battery current which is not from the ADC
     }
 
-    if (currentADCPin >= 0) {
+    // voltage available: get the number of cells if possible, desired and not armed
+    GetNbCells(&batterySettings, &flightBatteryData);
+
+    // ad a plausibility check: zero voltage => zero current
+    if (currentADCPin >= 0 /*&& flightBatteryData.Voltage <= 0.f*/) {
         flightBatteryData.Current = (PIOS_ADC_PinGetVolt(currentADCPin) - batterySettings.SensorCalibrations.CurrentZero) * batterySettings.SensorCalibrations.CurrentFactor; // in Amps
         if (flightBatteryData.Current > flightBatteryData.PeakCurrent) {
             flightBatteryData.PeakCurrent = flightBatteryData.Current; // in Amps
@@ -149,7 +158,11 @@ static void onTimer(__attribute__((unused)) UAVObjEvent *ev)
         flightBatteryData.Current = -0; // Dummy placeholder value. This is in case we get another source of battery current which is not from the ADC
     }
 
-    flightBatteryData.ConsumedEnergy += (flightBatteryData.Current * dT * 1000.0f / 3600.0f); // in mAh
+    // For safety reasons consider only positive currents in energy comsumption, i.e. no charging up.
+    // necesary when sensor are not perfectly calibrated
+    if (flightBatteryData.Current > 0) {
+        flightBatteryData.ConsumedEnergy += (flightBatteryData.Current * dT * 1000.0f / 3600.0f); // in mAh
+    }
 
     // Apply a 2 second rise time low-pass filter to average the current
     float alpha = 1.0f - dT / (dT + 2.0f);
@@ -184,9 +197,9 @@ static void onTimer(__attribute__((unused)) UAVObjEvent *ev)
 
         // FIXME: should make the battery voltage detection dependent on battery type.
         /*Not so sure. Some users will want to run their batteries harder than others, so it should be the user's choice. [KDS]*/
-        if (flightBatteryData.Voltage < batterySettings.CellVoltageThresholds.Alarm * batterySettings.NbCells) {
+        if (flightBatteryData.Voltage < batterySettings.CellVoltageThresholds.Alarm * flightBatteryData.NbCells) {
             AlarmsSet(SYSTEMALARMS_ALARM_BATTERY, SYSTEMALARMS_ALARM_CRITICAL);
-        } else if (flightBatteryData.Voltage < batterySettings.CellVoltageThresholds.Warning * batterySettings.NbCells) {
+        } else if (flightBatteryData.Voltage < batterySettings.CellVoltageThresholds.Warning * flightBatteryData.NbCells) {
             AlarmsSet(SYSTEMALARMS_ALARM_BATTERY, SYSTEMALARMS_ALARM_WARNING);
         } else {
             AlarmsClear(SYSTEMALARMS_ALARM_BATTERY);
@@ -196,6 +209,70 @@ static void onTimer(__attribute__((unused)) UAVObjEvent *ev)
     FlightBatteryStateSet(&flightBatteryData);
 }
 
+
+static int8_t GetNbCells(const FlightBatterySettingsData *batterySettings, FlightBatteryStateData *flightBatteryData)
+{
+    // get flight status to check for armed
+    FlightStatusData flightStatus;
+
+    FlightStatusGet(&flightStatus);
+
+    // check only if not armed
+    if (flightStatus.Armed == FLIGHTSTATUS_ARMED_ARMED) {
+        return -2;
+    }
+
+    // prescribed number of cells?
+    if (batterySettings->NbCells != 0) {
+        flightBatteryData->NbCells = batterySettings->NbCells;
+        flightBatteryData->NbCellsAutodetected = 0;
+        return -3;
+    }
+
+    // plausibility check
+    if (flightBatteryData->Voltage <= 0.5f) {
+        // cannot detect number of cells
+        flightBatteryData->NbCellsAutodetected = 0;
+        return -1;
+    }
+
+    float voltageMin = 0.f, voltageMax = 0.f;
+
+    // Cell type specific values
+    // TODO: could be implemented as constant arrays indexed by cellType
+    // or could be part of the UAVObject definition
+    switch (batterySettings->Type) {
+    case FLIGHTBATTERYSETTINGS_TYPE_LIPO:
+    case FLIGHTBATTERYSETTINGS_TYPE_LICO:
+        voltageMin = 3.6f;
+        voltageMax = 4.2f;
+        break;
+    case FLIGHTBATTERYSETTINGS_TYPE_A123:
+        voltageMin = 2.01f;
+        voltageMax = 3.59f;
+        break;
+    case FLIGHTBATTERYSETTINGS_TYPE_LIFESO4:
+    default:
+        flightBatteryData->NbCellsAutodetected = 0;
+        return -1;
+    }
+
+    // uniquely measurable under any condition iff n * voltageMax < (n+1) * voltageMin
+    // or n < voltageMin / (voltageMax-voltageMin)
+    // weaken condition by setting n <= voltageMin / (voltageMax-voltageMin) and
+    // checking for v <= voltageMin * voltageMax / (voltageMax-voltageMin)
+    if (flightBatteryData->Voltage > voltageMin * voltageMax / (voltageMax - voltageMin)) {
+        flightBatteryData->NbCellsAutodetected = 0;
+        return -1;
+    }
+
+
+    flightBatteryData->NbCells = (int8_t)(flightBatteryData->Voltage / voltageMin);
+    flightBatteryData->NbCellsAutodetected = 1;
+
+    return flightBatteryData->NbCells;
+}
+
 /**
  * @}
  */

shared/uavobjectdefinition/flightbatterysettings.xml

@@ -3,9 +3,8 @@
         <description>Flight Battery configuration.</description>
         
         <field name="Type" units="" type="enum" elements="1" options="LiPo,A123,LiCo,LiFeSO4,None" defaultvalue="LiPo"/>
-        <field name="NbCells" units=""  type="uint8"  elements="1" defaultvalue="3"/>
+        <field name="NbCells" units=""  type="uint8"  elements="1" defaultvalue="0"/>
         <field name="Capacity" units="mAh"  type="uint32"  elements="1" defaultvalue="2200"/>
-
         <field name="CellVoltageThresholds" units="V"  type="float" elementnames="Warning, Alarm" defaultvalue="3.4,3.1"/>
         <field name="SensorCalibrations" units="" type="float" elementnames="VoltageFactor, CurrentFactor, VoltageZero, CurrentZero" defaultvalue="1.0, 1.0, 0.0, 0.0"/>
         <access gcs="readwrite" flight="readwrite"/>

shared/uavobjectdefinition/flightbatterystate.xml

@@ -8,6 +8,9 @@
 	<field name="AvgCurrent" units="A" type="float"  elements="1" defaultvalue="0.0"/>
 	<field name="ConsumedEnergy" units="mAh" type="float" elements="1" defaultvalue="0.0"/>           
  	<field name="EstimatedFlightTime" units="sec"  type="float"  elements="1" defaultvalue="0.0"/>
+ 	<field name="NbCells" units=""  type="uint8"  elements="1" defaultvalue="3"/>
+ 	<field name="NbCellsAutodetected" units="bool" type="enum" elements="1" options="False,True" defaultvalue="False"/>
+ 	
         <access gcs="readonly" flight="readwrite"/>
         <telemetrygcs acked="false" updatemode="manual" period="0"/>
         <telemetryflight acked="false" updatemode="periodic" period="1000"/>