fix(battery): Debounce battery connected state in battery library

This robustifies against some communication flukes where a single 0V
sample was given to the battery library, which would previously mark the
battery disconnected immediately. Now we tolerate a given time of 0V
samples (while not actually updating the voltage) before considering the
battery disconnected.

src/lib/battery/battery.cpp

@@ -98,7 +98,10 @@ Battery::Battery(int index, ModuleParams *parent, const int sample_interval_us,
 
 void Battery::updateVoltage(const float voltage_v)
 {
-	_voltage_v = voltage_v;
+	if (voltage_v >= LITHIUM_BATTERY_RECOGNITION_VOLTAGE) {
+		_voltage_v = voltage_v;
+		_last_sufficient_voltage_timestamp = hrt_absolute_time();
+	}
 }
 
 void Battery::updateCurrent(const float current_a)
@@ -116,7 +119,8 @@ void Battery::updateBatteryStatus(const hrt_abstime &timestamp)
 	updateDt(timestamp);
 
 	// Require minimum voltage otherwise override connected status
-	if (_voltage_v < LITHIUM_BATTERY_RECOGNITION_VOLTAGE) {
+	// Tolerate a small number of low-voltage samples (common I2C comm failure) before disconnection
+	if (timestamp - _last_sufficient_voltage_timestamp > MAX_LOW_VOLTAGE_TIME_S * 1_s) {
 		_connected = false;
 	}
 

src/lib/battery/battery.h

@@ -134,8 +134,6 @@ public:
 	void updateDt(const hrt_abstime &timestamp);
 
 protected:
-	static constexpr float LITHIUM_BATTERY_RECOGNITION_VOLTAGE = 2.1f;
-
 	struct {
 		param_t v_empty;
 		param_t v_charged;
@@ -202,6 +200,10 @@ private:
 	bool _vehicle_status_is_fw{false};
 	hrt_abstime _last_unconnected_timestamp{0};
 
+	static constexpr float LITHIUM_BATTERY_RECOGNITION_VOLTAGE = 2.1f;
+	static constexpr float MAX_LOW_VOLTAGE_TIME_S = 0.2f;
+	hrt_abstime _last_sufficient_voltage_timestamp{0};
+
 	// Internal Resistance estimation
 	void updateInternalResistanceEstimation(const float voltage_v, const float current_a);
 	void resetInternalResistanceEstimation(const float voltage_v, const float current_a);

src/modules/simulation/battery_simulator/BatterySimulator.cpp

@@ -109,6 +109,12 @@ void BatterySimulator::Run()
 		vbatt = _battery.empty_cell_voltage();
 	}
 
+	if (_zero_volt_spike) {
+		// Zero volt but only one sample. Replicates some I2C comm failures
+		vbatt = 0.0f;
+		_zero_volt_spike = false;
+	}
+
 	vbatt *= _battery.cell_count();
 
 	_battery.setConnected(true);
@@ -157,6 +163,17 @@ void BatterySimulator::updateCommands()
 					supported = true;
 					_force_empty_battery = true;
 				}
+
+			} else if (failure_type == vehicle_command_s::FAILURE_TYPE_INTERMITTENT) {
+				handled = true;
+				PX4_WARN("CMD_INJECT_FAILURE, battery intermittent (single 0V sample)");
+				supported = true;
+
+				if (instance == 0) {
+					supported = true;
+					_zero_volt_spike = true;
+				}
+
 			}
 		}
 

src/modules/simulation/battery_simulator/BatterySimulator.hpp

@@ -89,6 +89,7 @@ private:
 	bool _armed{false};
 
 	bool _force_empty_battery{false};
+	bool _zero_volt_spike{false};
 
 	perf_counter_t	_loop_perf{perf_alloc(PC_ELAPSED, MODULE_NAME": cycle")};