fix(ina2xx): Reject exact zero readings

INA220 special case: only reject zero readings when output goes to
battery library, which if not updated just keeps the previous value.
When output goes to power_monitor uOrb message, publish zero readings as
well, as we do not have the option of publishing only a subset of
readings.

src/drivers/power_monitor/ina220/ina220.cpp

@@ -247,8 +247,16 @@ INA220::collect()
 	switch (_ch_type) {
 	case PM_CH_TYPE_VBATT: {
 			_battery.setConnected(success);
-			_battery.updateVoltage(_voltage);
-			_battery.updateCurrent(_current);
+
+			// Sometimes the read operation "succeeds" but results in wrong
+			// zero readings. Given that with noise a true reading of
+			// exactly 0 is very improbable, we just ignore those readings.
+			// The battery library keeps the old value.
+
+			if (_bus_voltage) { _battery.updateVoltage(_voltage); }
+
+			if (_bus_current) { _battery.updateCurrent(_current); }
+
 			_battery.updateAndPublishBatteryStatus(hrt_absolute_time());
 		}
 		break;

src/drivers/power_monitor/ina226/ina226.cpp

@@ -227,8 +227,15 @@ INA226::collect()
 	// success = success && (read(INA226_REG_SHUNTVOLTAGE, _shunt) == PX4_OK);
 
 	if (setConnected(success)) {
-		_battery.updateVoltage(static_cast<float>(_bus_voltage * INA226_VSCALE));
-		_battery.updateCurrent(static_cast<float>(_current * _current_lsb));
+
+		// Sometimes the read operation "succeeds" but results in wrong
+		// zero readings. Given that with noise a true reading of
+		// exactly 0 is very improbable, we just ignore those readings.
+		// The battery library keeps the old value.
+
+		if (_bus_voltage) { _battery.updateVoltage(static_cast<float>(_bus_voltage * INA226_VSCALE)); }
+
+		if (_current) { _battery.updateCurrent(static_cast<float>(_current * _current_lsb)); }
 	}
 
 	_battery.updateAndPublishBatteryStatus(hrt_absolute_time());

src/drivers/power_monitor/ina228/ina228.cpp

@@ -322,8 +322,16 @@ INA228::collect()
 	success = success && (read(INA228_REG_DIETEMP, _temperature) == PX4_OK);
 
 	if (setConnected(success)) {
-		_battery.updateVoltage(static_cast<float>(_bus_voltage * INA228_VSCALE));
-		_battery.updateCurrent(static_cast<float>(_current * _current_lsb));
+
+		// Sometimes the read operation "succeeds" but results in wrong
+		// zero readings. Given that with noise a true reading of
+		// exactly 0 is very improbable, we just ignore those readings.
+		// The battery library keeps the old value.
+
+		if (_bus_voltage) { _battery.updateVoltage(static_cast<float>(_bus_voltage * INA228_VSCALE)); }
+
+		if (_current) { _battery.updateCurrent(static_cast<float>(_current * _current_lsb)); }
+
 		_battery.updateTemperature(static_cast<float>(_temperature * INA228_TSCALE));
 	}
 

src/drivers/power_monitor/ina238/ina238.cpp

@@ -251,9 +251,17 @@ int INA238::collect()
 	success = success && (RegisterRead(Register::DIETEMP, (uint16_t &)temperature) == PX4_OK);
 
 	if (setConnected(success)) {
-		_battery.updateVoltage(static_cast<float>(bus_voltage * INA238_VSCALE));
-		_battery.updateCurrent(static_cast<float>(current * _current_lsb));
-		_battery.updateTemperature(static_cast<float>(temperature * INA238_TSCALE));
+
+		// Sometimes the read operation "succeeds" but results in wrong
+		// zero readings. Given that with noise a true reading of
+		// exactly 0 is very improbable, we just ignore those readings.
+		// The battery library keeps the old value.
+
+		if (bus_voltage) { _battery.updateVoltage(static_cast<float>(bus_voltage * INA238_VSCALE)); }
+
+		if (current) { _battery.updateCurrent(static_cast<float>(current * _current_lsb)); }
+
+		if (temperature) { _battery.updateTemperature(static_cast<float>(temperature * INA238_TSCALE)); }
 
 		_battery.updateAndPublishBatteryStatus(hrt_absolute_time());
 	}