Reduce angle drift adding level correction to the estimator

Utilize a-priori knowledge that the overall average attitude of the flying drone is level.

README.md

@@ -77,7 +77,7 @@ Additional articles:
 |Motor|8520 3.7V brushed motor.<br>Motor with exact 3.7V voltage is needed, not ranged working voltage (3.7V — 6V).<br>Make sure the motor shaft diameter and propeller hole diameter match!|<img src="docs/img/motor.jpeg" width=100>|4|
 |Propeller|55 mm (alternatively 65 mm)|<img src="docs/img/prop.jpg" width=100>|4|
 |MOSFET (transistor)|100N03A or [analog](https://t.me/opensourcequadcopter/33)|<img src="docs/img/100n03a.jpg" width=100>|4|
-|Pull-down resistor|10 kΩ|<img src="docs/img/resistor10k.jpg" width=100>|4|
+|Pull-down resistor<br>Voltage measurement resistor|10 kΩ|<img src="docs/img/resistor10k.jpg" width=100>|6|
 |3.7V Li-Po battery|LW 952540 (or any compatible by the size)|<img src="docs/img/battery.jpg" width=100>|1|
 |Battery connector cable|MX2.0 2P female|<img src="docs/img/mx.png" width=100>|1|
 |Li-Po Battery charger|Any|<img src="docs/img/charger.jpg" width=100>|1|
@@ -154,7 +154,11 @@ You can see a user-contributed [variant of complete circuit diagram](https://mir
   |VIN|VCC (or 3.3V depending on the receiver)|
   |Signal (TX)|GPIO4¹|
 
-*¹ — UART2 RX pin was [changed](https://docs.espressif.com/projects/arduino-esp32/en/latest/migration_guides/2.x_to_3.0.html#id14) to GPIO4 in Arduino ESP32 core 3.0.*
+  *¹ — UART2 RX pin was [changed](https://docs.espressif.com/projects/arduino-esp32/en/latest/migration_guides/2.x_to_3.0.html#id14) to GPIO4 in Arduino ESP32 core 3.0.*
+
+* Optionally connect the battery voltage divider for voltage monitoring to any ADC1 pin (e. g. *GPIO32* on ESP32, *GPIO3* on ESP32S3).
+
+  ESP32 and ESP32S3 [can measure](https://docs.espressif.com/projects/arduino-esp32/en/latest/api/adc.html#analogsetattenuation) up to 3.1 V and ESP32S3/ESP32C3 can measure up to 2.5 V, so choose the voltage divider resistors accordingly.
 
 ## Resources
 

docs/usage.md

@@ -112,7 +112,7 @@ You can also work with parameters using `p` command in the console. Parameter na
 
 ### Define IMU orientation
 
-Use parameters, to define the IMU board axes orientation relative to the drone's axes: `IMU_ROT_ROLL`, `IMU_ROT_PITCH`, and `IMU_ROT_YAW`.
+The IMU orientation (relative to the drone's axes) is defined using the parameters: `IMU_ROT_ROLL`, `IMU_ROT_PITCH`, and `IMU_ROT_YAW`.
 
 The drone has *X* axis pointing forward, *Y* axis pointing left, and *Z* axis pointing up, and the supported IMU boards have *X* axis pointing to the pins side and *Z* axis pointing up from the component side:
 
@@ -138,6 +138,8 @@ Before flight you need to calibrate the accelerometer:
 
 If using non-default motor pins, set the pin numbers using the parameters: `MOTOR_PIN_FL`, `MOTOR_PIN_FR`, `MOTOR_PIN_RL`, `MOTOR_PIN_RR` (front-left, front-right, rear-left, rear-right respectively).
 
+Certain ESP32 models (such as ESP32-S3) support a lower maximum PWM frequency; on these boards the parameter `MOT_PWM_FREQ` should be set to 40000 Hz.
+
 If using brushless motors and ESCs:
 
 1. Set the appropriate PWM using the parameters: `MOT_PWM_STOP`, `MOT_PWM_MIN`, and `MOT_PWM_MAX` (1000, 1000, and 2000 is typical).
@@ -146,6 +148,15 @@ If using brushless motors and ESCs:
 > [!CAUTION]
 > **Remove the props when configuring the motors!** If improperly configured, you may not be able to stop them.
 
+### Battery voltage monitoring
+
+ESP32 ADC can measure only up to 3.3 V, so you need to use a voltage divider to monitor the battery voltage. To enable voltage measurement, set the following parameters:
+
+1. `PWR_VOLT_PIN` — GPIO pin number where the voltage divider is connected (*-1* to disable).
+2. `PWR_VOLT_SCALE` — voltage divider coefficient (*2* for two equal resistors).
+
+After this setup, you should see the battery voltage in QGroundControl top panel or using `pw` command in the console.
+
 ### Important: check everything works
 
 1. Check the IMU is working: perform `imu` command in the console and check the output:
@@ -236,7 +247,7 @@ When finished flying, **disarm** the drone, moving the left stick to the bottom
 
 ### Flight modes
 
-Flight mode is changed using mode switch on the remote control (if configured) or using the console commands. The main flight mode is *STAB*.
+Flight mode is changed using mode switch on the remote control (if configured) or using the console commands. The main flight mode is *STAB*. In order to change modes using SBUS remote control, set the parameters: `CTL_FLT_MODE_0`, `CTL_FLT_MODE_1`, and `CTL_FLT_MODE_2` to required mode numbers (0 for *RAW*, 1 for *ACRO*, 2 for *STAB*, 3 for *AUTO*).
 
 #### STAB
 
@@ -257,7 +268,7 @@ In this mode, the pilot controls the angular rates. This control method is diffi
 
 In this mode, the pilot inputs are ignored (except the mode switch). The drone can be controlled using [pyflix](../tools/pyflix/) Python library, or by modifying the firmware to implement the needed behavior.
 
-If the pilot moves the control sticks, the drone will switch back to *STAB* mode.
+If the pilot moves the control sticks and mode switch is not configured, the drone will switch back to *STAB* mode.
 
 ## Wi-Fi configuration
 

flix/cli.ino

@@ -16,6 +16,7 @@ extern float controlTime;
 extern int mode;
 extern bool armed;
 extern LowPassFilter<Vector> gyroBiasFilter;
+extern float voltage;
 
 const char* motd =
 "\nWelcome to\n"
@@ -39,6 +40,7 @@ const char* motd =
 "disarm - disarm the drone\n"
 "raw/stab/acro/auto - set mode\n"
 "rc - show RC data\n"
+"pw - show power info\n"
 "wifi - show Wi-Fi info\n"
 "ap <ssid> <password> - setup Wi-Fi access point\n"
 "sta <ssid> <password> - setup Wi-Fi client mode\n"
@@ -135,6 +137,8 @@ void doCommand(String str, bool echo = false) {
 		print("time: %.1f\n", controlTime);
 		print("mode: %s\n", getModeName());
 		print("armed: %d\n", armed);
+	} else if (command == "pw") {
+		print("Voltage: %.1f V\n", voltage);
 	} else if (command == "wifi") {
 		printWiFiInfo();
 	} else if (command == "ap") {
@@ -174,7 +178,7 @@ void doCommand(String str, bool echo = false) {
 			String core = systemState[i].xCoreID == tskNO_AFFINITY ? "*" : String(systemState[i].xCoreID);
 			int cpuPercentage = systemState[i].ulRunTimeCounter / (totalRunTime / 100);
 			print("%-5d%-20s%-7d%-6d%-6s%d\n",systemState[i].xTaskNumber, systemState[i].pcTaskName,
-				systemState[i].usStackHighWaterMark, systemState[i].uxCurrentPriority, core, cpuPercentage);
+				systemState[i].usStackHighWaterMark, systemState[i].uxCurrentPriority, core.c_str(), cpuPercentage);
 		}
 		delete[] systemState;
 #endif

flix/control.ino

@@ -67,7 +67,7 @@ void control() {
 
 void interpretControls() {
 	if (controlMode < 0.25) mode = flightModes[0];
-	else if (controlMode < 0.75) mode = flightModes[1];
+	else if (controlMode <= 0.75) mode = flightModes[1];
 	else if (controlMode > 0.75) mode = flightModes[2];
 
 	if (mode == AUTO) return; // pilot is not effective in AUTO mode
@@ -149,12 +149,25 @@ void controlTorque() {
 	motors[MOTOR_REAR_LEFT] = thrustTarget + torqueTarget.x + torqueTarget.y - torqueTarget.z;
 	motors[MOTOR_REAR_RIGHT] = thrustTarget - torqueTarget.x + torqueTarget.y + torqueTarget.z;
 
+	desaturate(motors[MOTOR_FRONT_LEFT], motors[MOTOR_FRONT_RIGHT], motors[MOTOR_REAR_LEFT], motors[MOTOR_REAR_RIGHT]);
+
 	motors[0] = constrain(motors[0], 0, 1);
 	motors[1] = constrain(motors[1], 0, 1);
 	motors[2] = constrain(motors[2], 0, 1);
 	motors[3] = constrain(motors[3], 0, 1);
 }
 
+void desaturate(float& a, float& b, float& c, float& d) {
+	float maxThrust = max(max(a, b), max(c, d));
+	if (maxThrust > 1) {
+		float diff = maxThrust - 1;
+		a -= diff;
+		b -= diff;
+		c -= diff;
+		d -= diff;
+	}
+}
+
 const char* getModeName() {
 	switch (mode) {
 		case RAW: return "RAW";

flix/estimate.ino

@@ -13,11 +13,13 @@ Quaternion attitude; // estimated attitude
 bool landed;
 
 float accWeight = 0.003;
+float levelWeight = 0.0002;
 LowPassFilter<Vector> ratesFilter(0.2); // cutoff frequency ~ 40 Hz
 
 void estimate() {
 	applyGyro();
 	applyAcc();
+	applyLevel();
 }
 
 void applyGyro() {
@@ -42,3 +44,12 @@ void applyAcc() {
 	// apply correction
 	attitude = Quaternion::rotate(attitude, Quaternion::fromRotationVector(correction));
 }
+
+void applyLevel() {
+	if (landed) return;
+
+	// assume the pilot keeps the drone more or less level in flight
+	Vector up = Quaternion::rotateVector(Vector(0, 0, 1), attitude);
+	Vector correction = Vector::rotationVectorBetween(Vector(0, 0, 1), up) * levelWeight;
+	attitude = Quaternion::rotate(attitude, Quaternion::fromRotationVector(correction));
+}

flix/flix.ino

@@ -18,8 +18,8 @@ extern float motors[4];
 void setup() {
 	Serial.begin(115200);
 	print("Initializing flix\n");
-	disableBrownOut();
 	setupParameters();
+	setupPower();
 	setupLED();
 	setLED(true);
 	setupMotors();
@@ -39,6 +39,7 @@ void loop() {
 	sendMotors();
 	handleInput();
 	processMavlink();
+	readVoltage();
 	logData();
 	syncParameters();
 }

flix/imu.ino

@@ -121,7 +121,7 @@ void printIMUInfo() {
 	print("model: %s\n", imu.getModel());
 	print("who am I: 0x%02X\n", imu.whoAmI());
 	print("rate: %.0f\n", loopRate);
-	print("gyro: %f %f %f\n", rates.x, rates.y, rates.z);
+	print("gyro: %f %f %f\n", gyro.x, gyro.y, gyro.z);
 	print("acc: %f %f %f\n", acc.x, acc.y, acc.z);
 	imu.waitForData();
 	Vector rawGyro, rawAcc;

flix/mavlink.ino

@@ -7,6 +7,7 @@
 #include "util.h"
 
 extern float controlTime;
+extern float voltage;
 
 int mavlinkSysId = 1;
 Rate telemetryFast(10);
@@ -39,6 +40,13 @@ void sendMavlink() {
 		mavlink_msg_extended_sys_state_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg,
 			MAV_VTOL_STATE_UNDEFINED, landed ? MAV_LANDED_STATE_ON_GROUND : MAV_LANDED_STATE_IN_AIR);
 		sendMessage(&msg);
+
+		uint16_t voltages[] = {voltage * 1000, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX, UINT16_MAX};
+		uint16_t voltagesExt[] = {0, 0, 0, 0};
+		float remaining = constrain(mapf(voltage, 3.4, 4.2, 0, 1), 0, 1);
+		mavlink_msg_battery_status_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, 0, MAV_BATTERY_FUNCTION_ALL,
+			MAV_BATTERY_TYPE_LIPO, INT16_MAX, voltages, -1, -1, -1, remaining * 100, 0, MAV_BATTERY_CHARGE_STATE_OK, voltagesExt, 0, 0);
+		sendMessage(&msg);
 	}
 
 	if (telemetryFast && mavlinkConnected) {
@@ -57,7 +65,7 @@ void sendMavlink() {
 		sendMessage(&msg);
 
 		mavlink_msg_scaled_imu_pack(mavlinkSysId, MAV_COMP_ID_AUTOPILOT1, &msg, time,
-			acc.x * 1000, -acc.y * 1000, -acc.z * 1000, // convert to frd
+			acc.x / ONE_G * 1000, -acc.y / ONE_G * 1000, -acc.z / ONE_G * 1000, // convert to frd
 			gyro.x * 1000, -gyro.y * 1000, -gyro.z * 1000,
 			0, 0, 0, 0);
 		sendMessage(&msg);

flix/parameters.ino

@@ -12,6 +12,9 @@ extern int rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel,
 extern int rcRxPin;
 extern int wifiMode, udpLocalPort, udpRemotePort;
 extern float rcLossTimeout, descendTime;
+extern int voltagePin;
+extern float voltageScale;
+extern LowPassFilter<float> voltageFilter;
 
 Preferences storage;
 
@@ -33,13 +36,16 @@ Parameter parameters[] = {
 	{"CTL_R_RATE_I", &rollRatePID.i},
 	{"CTL_R_RATE_D", &rollRatePID.d},
 	{"CTL_R_RATE_WU", &rollRatePID.windup},
+	{"CTL_R_RATE_D_A", &rollRatePID.lpf.alpha},
 	{"CTL_P_RATE_P", &pitchRatePID.p},
 	{"CTL_P_RATE_I", &pitchRatePID.i},
 	{"CTL_P_RATE_D", &pitchRatePID.d},
 	{"CTL_P_RATE_WU", &pitchRatePID.windup},
+	{"CTL_P_RATE_D_A", &pitchRatePID.lpf.alpha},
 	{"CTL_Y_RATE_P", &yawRatePID.p},
 	{"CTL_Y_RATE_I", &yawRatePID.i},
 	{"CTL_Y_RATE_D", &yawRatePID.d},
+	{"CTL_Y_RATE_D_A", &yawRatePID.lpf.alpha},
 	{"CTL_R_P", &rollPID.p},
 	{"CTL_R_I", &rollPID.i},
 	{"CTL_R_D", &rollPID.d},
@@ -67,6 +73,7 @@ Parameter parameters[] = {
 	{"IMU_GYRO_BIAS_A", &gyroBiasFilter.alpha},
 	// estimate
 	{"EST_ACC_WEIGHT", &accWeight},
+	{"EST_LVL_WEIGHT", &levelWeight},
 	{"EST_RATES_LPF_A", &ratesFilter.alpha},
 	// motors
 	{"MOT_PIN_FL", &motorPins[MOTOR_FRONT_LEFT], setupMotors},
@@ -109,6 +116,10 @@ Parameter parameters[] = {
 	{"MAV_SYS_ID", &mavlinkSysId},
 	{"MAV_RATE_SLOW", &telemetrySlow.rate},
 	{"MAV_RATE_FAST", &telemetryFast.rate},
+	// power
+	{"PWR_VOLT_PIN", &voltagePin},
+	{"PWR_VOLT_SCALE", &voltageScale},
+	{"PWR_VOLT_LPF_A", &voltageFilter.alpha},
 	// safety
 	{"SF_RC_LOSS_TIME", &rcLossTimeout},
 	{"SF_DESCEND_TIME", &descendTime},

flix/power.ino

@@ -0,0 +1,28 @@
+// Copyright (c) 2026 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Power management
+
+#include <soc/soc.h>
+#include <soc/rtc_cntl_reg.h>
+#include "lpf.h"
+#include "util.h"
+
+float voltage;
+LowPassFilter<float> voltageFilter(0.2);
+int voltagePin = -1;
+float voltageScale = 2;
+
+void setupPower() {
+	// Disable reset on low voltage
+	REG_CLR_BIT(RTC_CNTL_BROWN_OUT_REG, RTC_CNTL_BROWN_OUT_ENA);
+}
+
+void readVoltage() {
+	if (voltagePin < 0) return;
+	static Rate rate(10);
+	if (!rate) return;
+
+	float v = analogReadMilliVolts(voltagePin) * voltageScale / 1000.0f;
+	voltage = voltageFilter.update(v);
+}

flix/safety.ino

@@ -37,8 +37,8 @@ void descend() {
 void autoFailsafe() {
 	static float roll, pitch, yaw, throttle;
 	if (roll != controlRoll || pitch != controlPitch || yaw != controlYaw || abs(throttle - controlThrottle) > 0.05) {
-		// controls changed
-		if (mode == AUTO) mode = STAB; // regain control by the pilot
+		// controls changed and mode switch is not configured
+		if (mode == AUTO && invalid(controlMode)) mode = STAB; // regain control by the pilot
 	}
 	roll = controlRoll;
 	pitch = controlPitch;

flix/util.h

@@ -6,8 +6,6 @@
 #pragma once
 
 #include <math.h>
-#include <soc/soc.h>
-#include <soc/rtc_cntl_reg.h>
 
 const float ONE_G = 9.80665;
 extern float t;
@@ -35,11 +33,6 @@ float wrapAngle(float angle) {
 	return angle;
 }
 
-// Disable reset on low voltage
-void disableBrownOut() {
-	REG_CLR_BIT(RTC_CNTL_BROWN_OUT_REG, RTC_CNTL_BROWN_OUT_ENA);
-}
-
 // Trim and split string by spaces
 void splitString(String& str, String& token0, String& token1, String& token2) {
 	str.trim();

flix/vector.h

@@ -105,10 +105,23 @@ public:
 	}
 
 	static Vector rotationVectorBetween(const Vector& a, const Vector& b) {
+		float an = a.norm();
+		float bn = b.norm();
+		if (an < 1e-6 || bn < 1e-6) {
+			return Vector(0, 0, 0);
+		}
 		Vector direction = cross(a, b);
-		if (direction.zero()) {
-			// vectors are opposite, return any perpendicular vector
-			return cross(a, Vector(1, 0, 0));
+		if (direction.norm() < 1e-6) { // vectors are parallel
+			if (dot(a, b) > 0) { // same direction
+				return Vector(0, 0, 0);
+			}
+			// opposite direction
+			Vector perp = cross(a, Vector(1, 0, 0));
+			if (perp.norm() < 1e-6) {
+				perp = cross(a, Vector(0, 1, 0));
+			}
+			perp.normalize();
+			return perp * PI;
 		}
 		direction.normalize();
 		float angle = angleBetween(a, b);

flix/wifi.ino

@@ -25,6 +25,7 @@ void setupWiFi() {
 	} else if (wifiMode == W_STA) {
 		WiFi.begin(storage.getString("WIFI_STA_SSID", "").c_str(), storage.getString("WIFI_STA_PASS", "").c_str());
 	}
+	WiFi.setSleep(false); // disable power save
 	udp.begin(udpLocalPort);
 }
 

gazebo/Arduino.h

@@ -21,6 +21,8 @@
 #define degrees(rad) ((rad)*RAD_TO_DEG)
 
 #define constrain(amt,low,high) ((amt)<(low)?(low):((amt)>(high)?(high):(amt)))
+template<typename T> T max(T a, T b) { return a > b ? a : b; }
+template<typename T> T min(T a, T b) { return a < b ? a : b; }
 
 long map(long x, long in_min, long in_max, long out_min, long out_max) {
 	const long run = in_max - in_min;
@@ -166,6 +168,7 @@ void delay(uint32_t ms) {
 bool ledcAttach(uint8_t pin, uint32_t freq, uint8_t resolution) { return true; }
 bool ledcWrite(uint8_t pin, uint32_t duty) { return true; }
 uint32_t ledcChangeFrequency(uint8_t pin, uint32_t freq, uint8_t resolution) { return freq; }
+uint32_t analogReadMilliVolts(uint8_t pin) { return 0; }
 
 unsigned long __micros;
 unsigned long __resetTime = 0;

gazebo/flix.h

@@ -27,11 +27,13 @@ void step();
 void computeLoopRate();
 void applyGyro();
 void applyAcc();
+void applyLevel();
 void control();
 void interpretControls();
 void controlAttitude();
 void controlRates();
 void controlTorque();
+void desaturate(float& a, float& b, float& c, float& d);
 const char* getModeName();
 void sendMotors();
 int getDutyCycle(float value);

gazebo/simulator.cpp

@@ -27,6 +27,7 @@
 #include "mavlink.ino"
 #include "motors.ino"
 #include "parameters.ino"
+#include "power.ino"
 #include "rc.ino"
 #include "time.ino"
 

gazebo/soc/soc.h

@@ -1,4 +1,3 @@
 // Dummy file to make it possible to compile simulator with Flix' util.h
 
-#define WRITE_PERI_REG(addr, val) {}
 #define REG_CLR_BIT(_r, _b) {}

tools/example.py

@@ -10,6 +10,7 @@ print('Connected:', flix.connected)
 print('Mode:', flix.mode)
 print('Armed:', flix.armed)
 print('Landed:', flix.landed)
+print('Voltage:', flix.voltage, 'V')
 print('Rates:', *[f'{math.degrees(r):.0f}°/s' for r in flix.rates])
 print('Attitude:', *[f'{math.degrees(a):.0f}°' for a in flix.attitude_euler])
 print('Motors:', flix.motors)

tools/pyflix/README.md

@@ -24,19 +24,20 @@ pip install pyflix
 The API is accessed through the `Flix` class:
 
 ```python
-from flix import Flix
+from pyflix import Flix
 flix = Flix()  # create a Flix object and wait for connection
 ```
 
 ### Telemetry
 
-Basic telemetry is available through object properties. The property names generally match the corresponding variables in the firmware itself:
+Basic telemetry is available through object properties. The property names generally match the corresponding variables in the firmware code:
 
 ```python
 print(flix.connected)       # True if connected to the drone
 print(flix.mode)            # current flight mode (str)
 print(flix.armed)           # True if the drone is armed
 print(flix.landed)          # True if the drone is landed
+print(flix.voltage)         # battery voltage
 print(flix.attitude)        # attitude quaternion [w, x, y, z]
 print(flix.attitude_euler)  # attitude as Euler angles [roll, pitch, yaw]
 print(flix.rates)           # angular rates [roll_rate, pitch_rate, yaw_rate]
@@ -95,6 +96,7 @@ Full list of events:
 |`armed`|Armed state update|Armed state *(bool)*|
 |`mode`|Flight mode update|Flight mode *(str)*|
 |`landed`|Landed state update|Landed state *(bool)*|
+|`voltage`|Battery voltage update|Voltage *(float)*|
 |`print`|The drone prints text to the console|Text|
 |`attitude`|Attitude update|Attitude quaternion *(list)*|
 |`attitude_euler`|Attitude update|Euler angles *(list)*|

tools/pyflix/flix.py

@@ -26,6 +26,7 @@ class Flix:
     mode: str = ''
     armed: bool = False
     landed: bool = False
+    voltage: float = 0
     attitude: List[float]
     attitude_euler: List[float]  # roll, pitch, yaw
     rates: List[float]
@@ -68,7 +69,7 @@ class Flix:
         self._heartbeat_thread.start()
         if wait_connection:
             self.wait('mavlink.HEARTBEAT')
-            time.sleep(0.2) # give some time to receive initial state
+            time.sleep(0.6) # give some time to receive initial state
 
     def _init_state(self):
         self.attitude = [1, 0, 0, 0]
@@ -185,11 +186,16 @@ class Flix:
             self._trigger('motors', self.motors)
 
         if isinstance(msg, mavlink.MAVLink_scaled_imu_message):
-            self.acc = self._mavlink_to_flu([msg.xacc / 1000, msg.yacc / 1000, msg.zacc / 1000])
+            ONE_G = 9.80665
+            self.acc = self._mavlink_to_flu([msg.xacc * ONE_G / 1000, msg.yacc * ONE_G / 1000, msg.zacc * ONE_G / 1000])
             self.gyro = self._mavlink_to_flu([msg.xgyro / 1000, msg.ygyro / 1000, msg.zgyro / 1000])
             self._trigger('acc', self.acc)
             self._trigger('gyro', self.gyro)
 
+        if isinstance(msg, mavlink.MAVLink_battery_status_message):
+            self.voltage = msg.voltages[0] / 1000
+            self._trigger('voltage', self.voltage)
+
         if isinstance(msg, mavlink.MAVLink_serial_control_message):
             # new chunk of data
             text = bytes(msg.data)[:msg.count].decode('utf-8', errors='ignore')

tools/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "pyflix"
-version = "0.11"
+version = "0.14"
 description = "Python API for Flix drone"
 authors = [{ name="Oleg Kalachev", email="okalachev@gmail.com" }]
 license = "MIT"