Make some variables static

Apply PWM_VOLT_PIN without reboot.
Check if the voltage pin can be used with ADC when setting up.
Set voltage to NAN, when it's unknown (including pyflix).
pyflix@0.15.
Don't send BATTERY_STATUS when voltage is unknown.
Add dummy voltage to the simulator.

.vscode/c_cpp_properties.json

@@ -17,21 +17,7 @@
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
 				"~/.arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32/Arduino.h",
-				"~/.arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h",
-				"${workspaceFolder}/flix/cli.ino",
-				"${workspaceFolder}/flix/control.ino",
-				"${workspaceFolder}/flix/estimate.ino",
-				"${workspaceFolder}/flix/flix.ino",
-				"${workspaceFolder}/flix/imu.ino",
-				"${workspaceFolder}/flix/led.ino",
-				"${workspaceFolder}/flix/log.ino",
-				"${workspaceFolder}/flix/mavlink.ino",
-				"${workspaceFolder}/flix/motors.ino",
-				"${workspaceFolder}/flix/rc.ino",
-				"${workspaceFolder}/flix/time.ino",
-				"${workspaceFolder}/flix/wifi.ino",
-				"${workspaceFolder}/flix/parameters.ino",
-				"${workspaceFolder}/flix/safety.ino"
+				"~/.arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h"
 			],
 			"compilerPath": "~/.arduino15/packages/esp32/tools/esp-x32/2511/bin/xtensa-esp32-elf-g++",
 			"cStandard": "c11",
@@ -64,21 +50,7 @@
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
 				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32/Arduino.h",
-				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h",
-				"${workspaceFolder}/flix/flix.ino",
-				"${workspaceFolder}/flix/cli.ino",
-				"${workspaceFolder}/flix/control.ino",
-				"${workspaceFolder}/flix/estimate.ino",
-				"${workspaceFolder}/flix/imu.ino",
-				"${workspaceFolder}/flix/led.ino",
-				"${workspaceFolder}/flix/log.ino",
-				"${workspaceFolder}/flix/mavlink.ino",
-				"${workspaceFolder}/flix/motors.ino",
-				"${workspaceFolder}/flix/rc.ino",
-				"${workspaceFolder}/flix/time.ino",
-				"${workspaceFolder}/flix/wifi.ino",
-				"${workspaceFolder}/flix/parameters.ino",
-				"${workspaceFolder}/flix/safety.ino"
+				"~/Library/Arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h"
 			],
 			"compilerPath": "~/Library/Arduino15/packages/esp32/tools/esp-x32/2511/bin/xtensa-esp32-elf-g++",
 			"cStandard": "c11",
@@ -112,21 +84,7 @@
 			"forcedInclude": [
 				"${workspaceFolder}/.vscode/intellisense.h",
 				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.3.6/cores/esp32/Arduino.h",
-				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h",
-				"${workspaceFolder}/flix/cli.ino",
-				"${workspaceFolder}/flix/control.ino",
-				"${workspaceFolder}/flix/estimate.ino",
-				"${workspaceFolder}/flix/flix.ino",
-				"${workspaceFolder}/flix/imu.ino",
-				"${workspaceFolder}/flix/led.ino",
-				"${workspaceFolder}/flix/log.ino",
-				"${workspaceFolder}/flix/mavlink.ino",
-				"${workspaceFolder}/flix/motors.ino",
-				"${workspaceFolder}/flix/rc.ino",
-				"${workspaceFolder}/flix/time.ino",
-				"${workspaceFolder}/flix/wifi.ino",
-				"${workspaceFolder}/flix/parameters.ino",
-				"${workspaceFolder}/flix/safety.ino"
+				"~/AppData/Local/Arduino15/packages/esp32/hardware/esp32/3.3.6/variants/d1_mini32/pins_arduino.h"
 			],
 			"compilerPath": "~/AppData/Local/Arduino15/packages/esp32/tools/esp-x32/2511/bin/xtensa-esp32-elf-g++.exe",
 			"cStandard": "c11",

Makefile

@@ -18,6 +18,10 @@ dependencies .dependencies:
 	arduino-cli lib install "MAVLink"@2.0.25
 	touch .dependencies
 
+upload_proxy: .dependencies
+	arduino-cli compile --fqbn $(BOARD) tools/espnow-proxy
+	arduino-cli upload --fqbn $(BOARD) -p "$(PORT)" tools/espnow-proxy
+
 gazebo/build cmake: gazebo/CMakeLists.txt
 	mkdir -p gazebo/build
 	cd gazebo/build && cmake ..

README.md

@@ -21,8 +21,8 @@
 * Dedicated for education and research.
 * Made from general-purpose components.
 * Simple and clean source code in Arduino (<2k lines firmware).
-* Connectivity using Wi-Fi and MAVLink protocol.
-* Control using USB gamepad, remote control or smartphone.
+* Communication using MAVLink protocol over Wi-Fi or ESP-NOW.
+* Control with USB gamepad, remote control or smartphone.
 * Wireless command line interface and analyzing.
 * Precise simulation with Gazebo.
 * Python library for scripting and automatic flights.

docs/usage.md

@@ -290,11 +290,8 @@ The Wi-Fi mode is chosen using `WIFI_MODE` parameter in QGroundControl or in the
 
 * `0` — Wi-Fi is disabled.
 * `1` — Access Point mode *(AP)* — the drone creates a Wi-Fi network.
-* `2` — Client mode *(STA)* — the drone connects to an existing Wi-Fi network.
-* `3` — *ESP-NOW (not implemented yet)*.
-
-> [!WARNING]
-> Tests showed that Client mode may cause **additional delays** in remote control (due to retranslations), so it's generally not recommended.
+* `2` — Client mode *(STA)* — the drone connects to an existing Wi-Fi network (may cause additional delays, so generally not recommended).
+* `3` — ESP-NOW mode — the drone uses ESP-NOW protocol for communication.
 
 The SSID and password are configured using the `ap` and `sta` console commands:
 
@@ -316,6 +313,37 @@ Disabling Wi-Fi:
 p WIFI_MODE 0
 ```
 
+### Using ESP-NOW
+
+[ESP-NOW](https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/network/esp_now.html) is a low level wireless communication protocol. It can provide lower latency, better reliability, and longer range than Wi-Fi. However, it requires a second ESP32 board to be used as a proxy for the computer.
+
+<img src="img/espnow-connection.jpg" width="600">
+
+To setup ESP-NOW communication:
+
+1. Flash the second ESP32 board with ESP-NOW proxy sketch: [`tools/espnow-proxy/espnow-proxy.ino`](../tools/espnow-proxy/espnow-proxy.ino). Use Arduino IDE or command line: `make upload_proxy`.
+
+2. Open Serial Monitor or use `make monitor` command. The ESP32 will print its MAC address and generated encryption key, for example:
+
+   ```
+   espnow 7a:c8:e3:eb:bf:e9 &PiuSysxP9+$L&5E
+   ```
+
+   Run this line as a console command on each drone you want to bind to this proxy board.
+
+3. Set the `WIFI_MODE` parameter to `3` on the drone:
+
+   ```
+   p WIFI_MODE 3
+   ```
+
+4. Go to the QGroundControl menu ⇒ *Application Settings* ⇒ *Comm Links*, add new link with the following settings:
+   * Name: ESP32.
+   * Type: Serial.
+   * Serial Port: choose the port of the proxy ESP32 board, e. g. `/dev/cu.usbserial-0001`.
+   * Baud Rate: 115200.
+5. Click *Save*. QGroundControl should connect to the drone using ESP-NOW and begin showing the telemetry.
+
 ## Flight log
 
 After the flight, you can download the flight log for analysis wirelessly. Use the following command on your computer for that:

flix/cli.cpp

@@ -3,6 +3,8 @@
 
 // Implementation of command line interface
 
+#include <Arduino.h>
+#include "flix.h"
 #include "pid.h"
 #include "vector.h"
 #include "util.h"
@@ -10,6 +12,7 @@
 
 extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRONT_LEFT;
 extern const int RAW, ACRO, STAB, AUTO;
+extern const int W_AP, W_STA, W_ESPNOW;
 extern float t, dt, loopRate;
 extern uint16_t channels[16];
 extern float controlTime;
@@ -45,6 +48,7 @@ const char* motd =
 "wifi - show Wi-Fi info\n"
 "ap <ssid> <password> - setup Wi-Fi access point\n"
 "sta <ssid> <password> - setup Wi-Fi client mode\n"
+"espnow <mac> [<key>] - setup ESP-NOW peer\n"
 "mot - show motor output\n"
 "log [dump] - print log header [and data]\n"
 "cr - calibrate RC\n"
@@ -74,7 +78,7 @@ void pause(float duration) {
 	}
 }
 
-void doCommand(String str, bool echo = false) {
+void doCommand(String str, bool echo) {
 	// parse command
 	String command, arg0, arg1;
 	splitString(str, command, arg0, arg1);
@@ -143,9 +147,11 @@ void doCommand(String str, bool echo = false) {
 	} else if (command == "wifi") {
 		printWiFiInfo();
 	} else if (command == "ap") {
-		configWiFi(true, arg0.c_str(), arg1.c_str());
+		configWiFi(W_AP, arg0.c_str(), arg1.c_str());
 	} else if (command == "sta") {
-		configWiFi(false, arg0.c_str(), arg1.c_str());
+		configWiFi(W_STA, arg0.c_str(), arg1.c_str());
+	} else if (command == "espnow") {
+		configWiFi(W_ESPNOW, arg0.c_str(), arg1.c_str());
 	} else if (command == "mot") {
 		print("front-right %g front-left %g rear-right %g rear-left %g\n",
 			motors[MOTOR_FRONT_RIGHT], motors[MOTOR_FRONT_LEFT], motors[MOTOR_REAR_RIGHT], motors[MOTOR_REAR_LEFT]);

flix/config.h

@@ -0,0 +1,55 @@
+// Wi-Fi
+#define WIFI_ENABLED 1
+#define WIFI_SSID "flix"
+#define WIFI_PASSWORD "flixwifi"
+#define WIFI_UDP_PORT 14550
+#define WIFI_UDP_REMOTE_PORT 14550
+#define WIFI_UDP_REMOTE_ADDR "255.255.255.255"
+
+// Motors
+#define MOTOR_0_PIN 12 // rear left
+#define MOTOR_1_PIN 13 // rear right
+#define MOTOR_2_PIN 14 // front right
+#define MOTOR_3_PIN 15 // front left
+#define PWM_FREQUENCY 78000
+#define PWM_RESOLUTION 10
+#define PWM_STOP 0
+#define PWM_MIN 0
+#define PWM_MAX 1000000 / PWM_FREQUENCY
+
+// Control
+#define PITCHRATE_P 0.05
+#define PITCHRATE_I 0.2
+#define PITCHRATE_D 0.001
+#define PITCHRATE_I_LIM 0.3
+#define ROLLRATE_P PITCHRATE_P
+#define ROLLRATE_I PITCHRATE_I
+#define ROLLRATE_D PITCHRATE_D
+#define ROLLRATE_I_LIM PITCHRATE_I_LIM
+#define YAWRATE_P 0.3
+#define YAWRATE_I 0.0
+#define YAWRATE_D 0.0
+#define YAWRATE_I_LIM 0.3
+#define ROLL_P 6
+#define ROLL_I 0
+#define ROLL_D 0
+#define PITCH_P ROLL_P
+#define PITCH_I ROLL_I
+#define PITCH_D ROLL_D
+#define YAW_P 3
+#define PITCHRATE_MAX radians(360)
+#define ROLLRATE_MAX radians(360)
+#define YAWRATE_MAX radians(300)
+#define TILT_MAX radians(30)
+#define RATES_D_LPF_ALPHA 0.2 // cutoff frequency ~ 40 Hz
+
+// Estimation
+#define WEIGHT_ACC 0.003
+#define RATES_LFP_ALPHA 0.2 // cutoff frequency ~ 40 Hz
+
+// MAVLink
+#define SYSTEM_ID 1
+
+// Safety
+#define RC_LOSS_TIMEOUT 1
+#define DESCEND_TIME 10

flix/control.cpp

@@ -3,38 +3,16 @@
 
 // Flight control
 
+#include "config.h"
+#include "flix.h"
 #include "vector.h"
 #include "quaternion.h"
 #include "pid.h"
 #include "lpf.h"
 #include "util.h"
 
-#define PITCHRATE_P 0.05
-#define PITCHRATE_I 0.2
-#define PITCHRATE_D 0.001
-#define PITCHRATE_I_LIM 0.3
-#define ROLLRATE_P PITCHRATE_P
-#define ROLLRATE_I PITCHRATE_I
-#define ROLLRATE_D PITCHRATE_D
-#define ROLLRATE_I_LIM PITCHRATE_I_LIM
-#define YAWRATE_P 0.3
-#define YAWRATE_I 0.0
-#define YAWRATE_D 0.0
-#define YAWRATE_I_LIM 0.3
-#define ROLL_P 6
-#define ROLL_I 0
-#define ROLL_D 0
-#define PITCH_P ROLL_P
-#define PITCH_I ROLL_I
-#define PITCH_D ROLL_D
-#define YAW_P 3
-#define PITCHRATE_MAX radians(360)
-#define ROLLRATE_MAX radians(360)
-#define YAWRATE_MAX radians(300)
-#define TILT_MAX radians(30)
-#define RATES_D_LPF_ALPHA 0.2 // cutoff frequency ~ 40 Hz
+extern const int RAW = 0, ACRO = 1, STAB = 2, AUTO = 3; // flight modes
 
-const int RAW = 0, ACRO = 1, STAB = 2, AUTO = 3; // flight modes
 int mode = STAB;
 bool armed = false;
 

flix/estimate.cpp

@@ -3,6 +3,8 @@
 
 // Attitude estimation using gyro and accelerometer
 
+#include "config.h"
+#include "flix.h"
 #include "quaternion.h"
 #include "vector.h"
 #include "lpf.h"

flix/flix.h

@@ -0,0 +1,95 @@
+// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// All-in-one header file
+
+#pragma once
+
+#include <Arduino.h>
+#include "vector.h"
+#include "quaternion.h"
+
+extern float t, dt;
+extern float loopRate;
+extern float controlRoll, controlPitch, controlYaw, controlThrottle, controlMode;
+extern Vector gyro, acc;
+extern Vector rates;
+extern Quaternion attitude;
+extern bool landed;
+extern int mode;
+extern bool armed;
+extern Quaternion attitudeTarget;
+extern Vector ratesTarget, ratesExtra, torqueTarget;
+extern float thrustTarget;
+extern float motors[4];
+
+void print(const char* format, ...);
+void pause(float duration);
+void doCommand(String str, bool echo = false);
+void handleInput();
+void control();
+void interpretControls();
+void controlAttitude();
+void controlRates();
+void controlTorque();
+void desaturate(float& a, float& b, float& c, float& d);
+const char *getModeName();
+void estimate();
+void applyGyro();
+void applyAcc();
+void applyLevel();
+void setupIMU();
+void configureIMU();
+void readIMU();
+void rotateIMU(Vector& data);
+void calibrateGyroOnce();
+void calibrateAccel();
+void calibrateAccelOnce();
+void printIMUCalibration();
+void printIMUInfo();
+void setupLED();
+void setLED(bool on);
+void blinkLED();
+void prepareLogData();
+void logData();
+void printLogHeader();
+void printLogData();
+void processMavlink();
+void sendMavlink();
+void sendMessage(const void *msg);
+void receiveMavlink();
+void printWiFiInfo();
+void configWiFi(int mode, const char *first, const char *second);
+void handleMavlink(const void *_msg);
+void mavlinkPrint(const char* str);
+void sendMavlinkPrint();
+void setupMotors();
+int getDutyCycle(float value);
+void sendMotors();
+bool motorsActive();
+void testMotor(int n);
+void setupParameters();
+int parametersCount();
+const char *getParameterName(int index);
+float getParameter(int index);
+float getParameter(const char *name);
+bool setParameter(const char *name, const float value);
+void syncParameters();
+void printParameters();
+void resetParameters();
+void setupRC();
+bool readRC();
+void normalizeRC();
+void calibrateRC();
+void calibrateRCChannel(int *channel, uint16_t in[16], uint16_t out[16], const char *str);
+void printRCCalibration();
+void setupPower();
+void failsafe();
+void rcLossFailsafe();
+void descend();
+void autoFailsafe();
+void step();
+void computeLoopRate();
+void setupWiFi();
+void sendWiFi(const uint8_t *buf, int len);
+int receiveWiFi(uint8_t *buf, int len);

flix/flix.ino

@@ -3,17 +3,11 @@
 
 // Main firmware file
 
+#include "config.h"
 #include "vector.h"
 #include "quaternion.h"
 #include "util.h"
-
-extern float t, dt;
-extern float controlRoll, controlPitch, controlYaw, controlThrottle, controlMode;
-extern Vector gyro, acc;
-extern Vector rates;
-extern Quaternion attitude;
-extern bool landed;
-extern float motors[4];
+#include "flix.h"
 
 void setup() {
 	Serial.begin(115200);

flix/led.cpp

@@ -3,6 +3,8 @@
 
 // Board's LED control
 
+#include <Arduino.h>
+
 #define BLINK_PERIOD 500000
 
 #ifndef LED_BUILTIN

flix/log.cpp

@@ -3,6 +3,7 @@
 
 // In-RAM logging
 
+#include "flix.h"
 #include "vector.h"
 #include "util.h"
 

flix/lpf.h

@@ -5,6 +5,8 @@
 
 #pragma once
 
+#include <Arduino.h>
+
 template <typename T> // Using template to make the filter usable for scalar and vector values
 class LowPassFilter {
 public:

flix/mavlink.cpp

@@ -3,18 +3,22 @@
 
 // MAVLink communication
 
+#include <Arduino.h>
 #include <MAVLink.h>
+#include "config.h"
 #include "util.h"
 
+extern const int RAW, ACRO, STAB, AUTO;
 extern float controlTime;
 extern float voltage;
+extern uint16_t channels[16];
 
 int mavlinkSysId = 1;
 Rate telemetryFast(10);
 Rate telemetrySlow(2);
 
 bool mavlinkConnected = false;
-String mavlinkPrintBuffer;
+static String mavlinkPrintBuffer;
 
 void processMavlink() {
 	sendMavlink();
@@ -46,7 +50,7 @@ void sendMavlink() {
 		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 (valid(voltage)) sendMessage(&msg);
 	}
 
 	if (telemetryFast && mavlinkConnected) {
@@ -211,6 +215,7 @@ void handleMavlink(const void *_msg) {
 		armed = motors[0] > 0 || motors[1] > 0 || motors[2] > 0 || motors[3] > 0;
 	}
 
+	/* TODO:
 	if (msg.msgid == MAVLINK_MSG_ID_LOG_REQUEST_DATA) {
 		mavlink_log_request_data_t m;
 		mavlink_msg_log_request_data_decode(&msg, &m);
@@ -224,6 +229,7 @@ void handleMavlink(const void *_msg) {
 			sendMessage(&msg);
 		}
 	}
+	*/
 
 	// Handle commands
 	if (msg.msgid == MAVLINK_MSG_ID_COMMAND_LONG) {

flix/motors.cpp

@@ -3,6 +3,9 @@
 
 // PWM control for motors
 
+#include <Arduino.h>
+#include "config.h"
+#include "flix.h"
 #include "util.h"
 
 float motors[4]; // normalized motor thrusts in range [0..1]
@@ -14,10 +17,7 @@ int pwmStop = 0;
 int pwmMin = 0;
 int pwmMax = -1; // -1 means duty cycle mode
 
-const int MOTOR_REAR_LEFT = 0;
-const int MOTOR_REAR_RIGHT = 1;
-const int MOTOR_FRONT_RIGHT = 2;
-const int MOTOR_FRONT_LEFT = 3;
+extern const int MOTOR_REAR_LEFT = 0, MOTOR_REAR_RIGHT = 1, MOTOR_FRONT_RIGHT = 2, MOTOR_FRONT_LEFT = 3;
 
 void setupMotors() {
 	print("Setup Motors\n");

flix/parameters.cpp

@@ -4,17 +4,32 @@
 // Parameters storage in flash memory
 
 #include <Preferences.h>
+#include "flix.h"
+#include "pid.h"
+#include "lpf.h"
 #include "util.h"
 
-extern int channelZero[16];
-extern int channelMax[16];
-extern int rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
-extern int rcRxPin;
-extern int wifiMode, udpLocalPort, udpRemotePort;
+extern float channelZero[16], channelMax[16];
+extern float rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
+extern float tiltMax;
+extern int flightModes[3];
+extern PID rollPID, pitchPID, yawPID;
+extern PID rollRatePID, pitchRatePID, yawRatePID;
+extern Vector maxRate;
+extern Vector imuRotation;
+extern Vector accBias, accScale;
+extern float accWeight, levelWeight;
+extern LowPassFilter<Vector> gyroBiasFilter, ratesFilter, voltageFilter;
+extern int rcRxPin, voltagePin;
+extern int motorPins[4];
+extern int pwmFrequency, pwmResolution, pwmStop, pwmMin, pwmMax;
+extern int wifiMode, wifiLongRange, udpLocalPort, udpRemotePort, espnowChannel;
+extern int mavlinkSysId;
+extern Rate telemetrySlow, telemetryFast;
 extern float rcLossTimeout, descendTime;
 extern int voltagePin;
 extern float voltageScale;
-extern LowPassFilter<float> voltageFilter;
+extern const int MOTOR_REAR_LEFT, MOTOR_REAR_RIGHT, MOTOR_FRONT_RIGHT, MOTOR_FRONT_LEFT;
 
 Preferences storage;
 
@@ -30,7 +45,7 @@ struct Parameter {
 	void setValue(const float value) { if (integer) *i = value; else *f = value; };
 };
 
-Parameter parameters[] = {
+static Parameter parameters[] = {
 	// control
 	{"CTL_R_RATE_P", &rollRatePID.p},
 	{"CTL_R_RATE_I", &rollRatePID.i},
@@ -112,12 +127,15 @@ Parameter parameters[] = {
 	{"WIFI_MODE", &wifiMode},
 	{"WIFI_PORT_LOC", &udpLocalPort},
 	{"WIFI_PORT_REM", &udpRemotePort},
+	{"WIFI_LONG_RANGE", &wifiLongRange},
+	// espnow
+	{"ESPNOW_CHANNEL", &espnowChannel},
 	// mavlink
 	{"MAV_SYS_ID", &mavlinkSysId},
 	{"MAV_RATE_SLOW", &telemetrySlow.rate},
 	{"MAV_RATE_FAST", &telemetryFast.rate},
 	// power
-	{"PWR_VOLT_PIN", &voltagePin},
+	{"PWR_VOLT_PIN", &voltagePin, setupPower},
 	{"PWR_VOLT_SCALE", &voltageScale},
 	{"PWR_VOLT_LPF_A", &voltageFilter.alpha},
 	// safety

flix/pid.h

@@ -5,6 +5,8 @@
 
 #pragma once
 
+#include "Arduino.h"
+#include "flix.h"
 #include "lpf.h"
 
 class PID {

flix/power.ino

@@ -8,14 +8,14 @@
 #include "lpf.h"
 #include "util.h"
 
-float voltage;
+float voltage = NAN;
 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);
+	REG_CLR_BIT(RTC_CNTL_BROWN_OUT_REG, RTC_CNTL_BROWN_OUT_ENA); // disable reset on low voltage
+	if (digitalPinToAnalogChannel(voltagePin) == -1) voltagePin = -1; // test ADC pin
 }
 
 void readVoltage() {

flix/quaternion.h

@@ -5,6 +5,7 @@
 
 #pragma once
 
+#include <Arduino.h>
 #include "vector.h"
 
 class Quaternion : public Printable {

flix/rc.cpp

@@ -6,7 +6,7 @@
 #include <SBUS.h>
 #include "util.h"
 
-SBUS rc(Serial1);
+static SBUS rc(Serial1);
 int rcRxPin = -1; // -1 means disabled
 
 uint16_t channels[16]; // raw rc channels

flix/safety.cpp

@@ -3,8 +3,12 @@
 
 // Fail-safe functions
 
+#include "config.h"
+#include "flix.h"
+#include "util.h"
+
 extern float controlTime;
-extern float controlRoll, controlPitch, controlThrottle, controlYaw;
+extern const int AUTO, STAB;
 
 float rcLossTimeout = 1;
 float descendTime = 10;

flix/time.cpp

@@ -3,6 +3,9 @@
 
 // Time related functions
 
+#include "Arduino.h"
+#include "flix.h"
+
 float t = NAN; // current time, s
 float dt; // time delta with the previous step, s
 float loopRate; // Hz

flix/util.h

@@ -6,24 +6,25 @@
 #pragma once
 
 #include <math.h>
+#include <ESP32_NOW_Serial.h>
+#include "flix.h"
 
 const float ONE_G = 9.80665;
-extern float t;
 
-float mapf(float x, float in_min, float in_max, float out_min, float out_max) {
+inline float mapf(float x, float in_min, float in_max, float out_min, float out_max) {
 	return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
 }
 
-bool invalid(float x) {
+inline bool invalid(float x) {
 	return !isfinite(x);
 }
 
-bool valid(float x) {
+inline bool valid(float x) {
 	return isfinite(x);
 }
 
 // Wrap angle to [-PI, PI)
-float wrapAngle(float angle) {
+inline float wrapAngle(float angle) {
 	angle = fmodf(angle, 2 * PI);
 	if (angle > PI) {
 		angle -= 2 * PI;
@@ -34,7 +35,7 @@ float wrapAngle(float angle) {
 }
 
 // Trim and split string by spaces
-void splitString(String& str, String& token0, String& token1, String& token2) {
+inline void splitString(String& str, String& token0, String& token1, String& token2) {
 	str.trim();
 	if (str.isEmpty()) return;
 	char chars[str.length() + 1];
@@ -46,6 +47,16 @@ void splitString(String& str, String& token0, String& token1, String& token2) {
 	if (token2.c_str() == NULL) token2 = "";
 }
 
+// Simplified ESP-NOW Serial without tx buffering and resends
+class ESPNOWSerial : public ESP_NOW_Serial_Class {
+public:
+	using ESP_NOW_Serial_Class::ESP_NOW_Serial_Class;
+	void onSent(bool success) override {} // disable resends
+	size_t write(const uint8_t *data, size_t len) override {
+		return ESP_NOW_Peer::send(data, len); // pure send without buffering
+	}
+};
+
 // Rate limiter
 class Rate {
 public:

flix/vector.h

@@ -5,6 +5,8 @@
 
 #pragma once
 
+#include <Arduino.h>
+
 class Vector : public Printable {
 public:
 	float x, y, z;
@@ -136,5 +138,5 @@ public:
 	}
 };
 
-Vector operator * (const float a, const Vector& b) { return b * a; }
-Vector operator + (const float a, const Vector& b) { return b + a; }
+inline Vector operator * (const float a, const Vector& b) { return b * a; }
+inline Vector operator + (const float a, const Vector& b) { return b + a; }

flix/wifi.cpp

@@ -0,0 +1,132 @@
+// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Wi-Fi and ESP-NOW communication
+
+#include <WiFi.h>
+#include <WiFiAP.h>
+#include <WiFiUdp.h>
+#include <MacAddress.h>
+#include <ESP32_NOW_Serial.h>
+#include <Preferences.h>
+#include "config.h"
+#include "flix.h"
+#include "util.h"
+
+extern Preferences storage; // use the main preferences storage
+extern bool mavlinkConnected;
+
+extern const int W_DISABLED = 0, W_AP = 1, W_STA = 2, W_ESPNOW = 3;
+int wifiMode = W_AP;
+
+int wifiLongRange = 0;
+int udpLocalPort = 14550;
+int udpRemotePort = 14550;
+static IPAddress udpRemoteIP = "255.255.255.255";
+static WiFiUDP udp;
+
+static ESPNOWSerial espnow(NULL, 0, WIFI_IF_AP);
+static ESPNOWSerial espnowBroadcast(ESP_NOW.BROADCAST_ADDR, 0, WIFI_IF_AP);
+int espnowChannel = 6;
+
+void setupWiFi() {
+	print("Setup Wi-Fi\n");
+	WiFi.enableLongRange(wifiLongRange);
+
+	if (wifiMode == W_AP) {
+		WiFi.softAP(storage.getString("WIFI_AP_SSID", "flix").c_str(), storage.getString("WIFI_AP_PASS", "flixwifi").c_str());
+		udp.begin(udpLocalPort);
+	} else if (wifiMode == W_STA) {
+		WiFi.begin(storage.getString("WIFI_STA_SSID", "").c_str(), storage.getString("WIFI_STA_PASS", "").c_str());
+		udp.begin(udpLocalPort);
+	} else if (wifiMode == W_ESPNOW) {
+		WiFi.mode(WIFI_AP);
+		WiFi.setChannel(espnowChannel);
+		espnow.addr(MacAddress(storage.getString("ESPNOW_PEER_MAC", "FF:FF:FF:FF:FF:FF").c_str()));
+		String key = storage.getString("ESPNOW_PEER_KEY", "");
+		espnow.setKey(key.isEmpty() ? nullptr : (const uint8_t *)key.c_str());
+		espnow.begin();
+		espnowBroadcast.begin();
+	}
+
+	WiFi.setSleep(false); // disable power save
+}
+
+void sendWiFi(const uint8_t *buf, int len) {
+	if (espnow) {
+		espnow.write(buf, len);
+		static Rate discovery(2);
+		if (discovery) espnowBroadcast.write((const uint8_t *)"flix", 4); // broadcast message to help finding this device
+		return;
+	}
+
+	if (WiFi.softAPgetStationNum() == 0 && !WiFi.isConnected()) return;
+
+	udp.beginPacket(udpRemoteIP, udpRemotePort);
+	udp.write(buf, len);
+	udp.endPacket();
+}
+
+int receiveWiFi(uint8_t *buf, int len) {
+	if (espnow) {
+		return espnow.read(buf, len);
+	}
+
+	if (WiFi.softAPgetStationNum() == 0 && !WiFi.isConnected()) return 0;
+
+	udp.parsePacket();
+	if (udp.remoteIP()) udpRemoteIP = udp.remoteIP();
+	return udp.read(buf, len);
+}
+
+void printWiFiInfo() {
+	if (espnow) {
+		print("Mode: ESP-NOW\n");
+		print("ESP-NOW version: %d\n", ESP_NOW.getVersion());
+		print("Max packet size: %d\n", ESP_NOW.getMaxDataLen());
+		print("MAC: %s\n", WiFi.softAPmacAddress().c_str());
+		print("Peer MAC: %s\n", MacAddress(espnow.addr()).toString().c_str());
+		print("Encrypted: %d\n", espnow.isEncrypted());
+		print("Channel: %d\n", espnow.getChannel());
+	} else if (WiFi.getMode() == WIFI_MODE_AP) {
+		print("Mode: Access Point (AP)\n");
+		print("MAC: %s\n", WiFi.softAPmacAddress().c_str());
+		print("SSID: %s\n", WiFi.softAPSSID().c_str());
+		print("Password: ***\n");
+		print("Channel: %d\n", WiFi.channel());
+		print("Clients: %d\n", WiFi.softAPgetStationNum());
+		print("IP: %s\n", WiFi.softAPIP().toString().c_str());
+		print("Remote IP: %s\n", udpRemoteIP.toString().c_str());
+	} else if (WiFi.getMode() == WIFI_MODE_STA) {
+		print("Mode: Client (STA)\n");
+		print("Connected: %d\n", WiFi.isConnected());
+		print("MAC: %s\n", WiFi.macAddress().c_str());
+		print("SSID: %s\n", WiFi.SSID().c_str());
+		print("Password: ***\n");
+		print("Channel: %d\n", WiFi.channel());
+		print("RSSI: %d dBm\n", WiFi.RSSI());
+		print("IP: %s\n", WiFi.localIP().toString().c_str());
+		print("Remote IP: %s\n", udpRemoteIP.toString().c_str());
+	} else {
+		print("Mode: Disabled\n");
+	}
+	print("MAVLink connected: %d\n", mavlinkConnected);
+}
+
+void configWiFi(int mode, const char *first, const char *second) {
+	MacAddress mac;
+	if (mode == W_AP && strlen(first) > 0 && strlen(second) >= 8) {
+		storage.putString("WIFI_AP_SSID", first);
+		storage.putString("WIFI_AP_PASS", second);
+	} else if (mode == W_STA && strlen(first) > 0 && strlen(second) >= 8) {
+		storage.putString("WIFI_STA_SSID", first);
+		storage.putString("WIFI_STA_PASS", second);
+	} else if (mode == W_ESPNOW && mac.fromString(first)) {
+		storage.putString("ESPNOW_PEER_MAC", first);
+		storage.putString("ESPNOW_PEER_KEY", strlen(second) == ESP_NOW_KEY_LEN ? second : "");
+	} else {
+		print("Invalid configuration\n");
+		return;
+	}
+	print("✓ Reboot to apply new settings\n");
+}

flix/wifi.ino

@@ -1,82 +0,0 @@
-// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
-// Repository: https://github.com/okalachev/flix
-
-// Wi-Fi communication
-
-#include <WiFi.h>
-#include <WiFiAP.h>
-#include <WiFiUdp.h>
-#include "Preferences.h"
-
-extern Preferences storage; // use the main preferences storage
-
-const int W_DISABLED = 0, W_AP = 1, W_STA = 2;
-int wifiMode = W_AP;
-int udpLocalPort = 14550;
-int udpRemotePort = 14550;
-IPAddress udpRemoteIP = "255.255.255.255";
-
-WiFiUDP udp;
-
-void setupWiFi() {
-	print("Setup Wi-Fi\n");
-	if (wifiMode == W_AP) {
-		WiFi.softAP(storage.getString("WIFI_AP_SSID", "flix").c_str(), storage.getString("WIFI_AP_PASS", "flixwifi").c_str());
-	} else if (wifiMode == W_STA) {
-		WiFi.begin(storage.getString("WIFI_STA_SSID", "").c_str(), storage.getString("WIFI_STA_PASS", "").c_str());
-	} else {
-		return;
-	}
-	WiFi.setSleep(false); // disable power save
-	udp.begin(udpLocalPort);
-}
-
-void sendWiFi(const uint8_t *buf, int len) {
-	if (WiFi.softAPgetStationNum() == 0 && !WiFi.isConnected()) return;
-	udp.beginPacket(udpRemoteIP, udpRemotePort);
-	udp.write(buf, len);
-	udp.endPacket();
-}
-
-int receiveWiFi(uint8_t *buf, int len) {
-	if (WiFi.softAPgetStationNum() == 0 && !WiFi.isConnected()) return 0;
-	udp.parsePacket();
-	if (udp.remoteIP()) udpRemoteIP = udp.remoteIP();
-	return udp.read(buf, len);
-}
-
-void printWiFiInfo() {
-	if (WiFi.getMode() == WIFI_MODE_AP) {
-		print("Mode: Access Point (AP)\n");
-		print("MAC: %s\n", WiFi.softAPmacAddress().c_str());
-		print("SSID: %s\n", WiFi.softAPSSID().c_str());
-		print("Password: ***\n");
-		print("Clients: %d\n", WiFi.softAPgetStationNum());
-		print("IP: %s\n", WiFi.softAPIP().toString().c_str());
-	} else if (WiFi.getMode() == WIFI_MODE_STA) {
-		print("Mode: Client (STA)\n");
-		print("Connected: %d\n", WiFi.isConnected());
-		print("MAC: %s\n", WiFi.macAddress().c_str());
-		print("SSID: %s\n", WiFi.SSID().c_str());
-		print("Password: ***\n");
-		print("IP: %s\n", WiFi.localIP().toString().c_str());
-		print("RSSI: %d dBm\n", WiFi.RSSI());
-	} else {
-		print("Mode: Disabled\n");
-		return;
-	}
-	print("Channel: %d\n", WiFi.channel());
-	print("Remote IP: %s\n", udpRemoteIP.toString().c_str());
-	print("MAVLink connected: %d\n", mavlinkConnected);
-}
-
-void configWiFi(bool ap, const char *ssid, const char *password) {
-	if (ap) {
-		storage.putString("WIFI_AP_SSID", ssid);
-		storage.putString("WIFI_AP_PASS", password);
-	} else {
-		storage.putString("WIFI_STA_SSID", ssid);
-		storage.putString("WIFI_STA_PASS", password);
-	}
-	print("✓ Reboot to apply new settings\n");
-}

gazebo/Arduino.h

@@ -168,6 +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; }
+int8_t digitalPinToAnalogChannel(uint8_t pin) { return -1; }
 uint32_t analogReadMilliVolts(uint8_t pin) { return 0; }
 
 unsigned long __micros;

gazebo/CMakeLists.txt

@@ -10,9 +10,23 @@ list(APPEND CMAKE_CXX_FLAGS "${GAZEBO_CXX_FLAGS}")
 
 set(FLIX_SOURCE_DIR ../flix)
 include_directories(${FLIX_SOURCE_DIR})
+set(FLIX_SOURCE_DIR ../flix)
+include_directories(${FLIX_SOURCE_DIR})
+set(FLIX_SOURCES
+  ${FLIX_SOURCE_DIR}/cli.cpp
+  ${FLIX_SOURCE_DIR}/control.cpp
+  ${FLIX_SOURCE_DIR}/estimate.cpp
+  ${FLIX_SOURCE_DIR}/safety.cpp
+  ${FLIX_SOURCE_DIR}/log.cpp
+  ${FLIX_SOURCE_DIR}/mavlink.cpp
+  ${FLIX_SOURCE_DIR}/motors.cpp
+  ${FLIX_SOURCE_DIR}/parameters.cpp
+  ${FLIX_SOURCE_DIR}/rc.cpp
+  ${FLIX_SOURCE_DIR}/time.cpp
+)
 
 set(CMAKE_BUILD_TYPE RelWithDebInfo)
-add_library(flix SHARED simulator.cpp)
+add_library(flix SHARED simulator.cpp ${FLIX_SOURCES})
 target_link_libraries(flix ${GAZEBO_LIBRARIES} ${SDL2_LIBRARIES})
 target_include_directories(flix PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 target_compile_options(flix PRIVATE -Wno-address-of-packed-member) # disable unneeded mavlink warnings

gazebo/ESP32_NOW_Serial.h

@@ -0,0 +1,12 @@
+// Dummy file for the simulator
+
+class ESP_NOW_Peer {
+protected:
+	size_t send(const uint8_t *data, int len) { return 0; }
+};
+
+class ESP_NOW_Serial_Class : public ESP_NOW_Peer {
+public:
+	virtual void onSent(bool success) {};
+	virtual size_t write(const uint8_t *data, size_t len) { return 0; };
+};

gazebo/flix.h

@@ -58,6 +58,7 @@ void handleMavlink(const void *_msg);
 void mavlinkPrint(const char* str);
 void sendMavlinkPrint();
 inline Quaternion fluToFrd(const Quaternion &q);
+void setupPower();
 void failsafe();
 void rcLossFailsafe();
 void descend();

gazebo/simulator.cpp

@@ -18,19 +18,6 @@
 #include "Arduino.h"
 #include "flix.h"
 
-#include "cli.ino"
-#include "control.ino"
-#include "estimate.ino"
-#include "safety.ino"
-#include "log.ino"
-#include "lpf.h"
-#include "mavlink.ino"
-#include "motors.ino"
-#include "parameters.ino"
-#include "power.ino"
-#include "rc.ino"
-#include "time.ino"
-
 using ignition::math::Vector3d;
 using namespace gazebo;
 using namespace std;
@@ -73,6 +60,8 @@ public:
 		gyro = Vector(imu->AngularVelocity().X(), imu->AngularVelocity().Y(), imu->AngularVelocity().Z());
 		acc = this->accFilter.update(Vector(imu->LinearAcceleration().X(), imu->LinearAcceleration().Y(), imu->LinearAcceleration().Z()));
 
+		voltage = 4.2f; // dummy voltage value
+
 		readRC();
 		estimate();
 

tools/espnow-proxy/README.md

@@ -0,0 +1,3 @@
+# ESPNOW-proxy
+
+Proxy sketch for using ESP-NOW connection with Flix drone.

tools/espnow-proxy/espnow-proxy.ino

@@ -0,0 +1,88 @@
+// Copyright (c) 2026 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Proxy for ESP-NOW connection
+
+#include <vector>
+#include <WiFi.h>
+#include <ESP32_NOW_Serial.h>
+#include <MacAddress.h>
+#include <MAVLink.h>
+#include <Preferences.h>
+#include "../../flix/util.h"
+
+const int CHANNEL = 6;
+char key[ESP_NOW_KEY_LEN + 1] = {0}; // with trailing null
+
+Preferences storage;
+
+std::vector<ESPNOWSerial *> peers;
+
+void onNewPeer(const esp_now_recv_info_t *info, const uint8_t *data, int len, void *arg) {
+	if (len != 4 || memcmp(data, "flix", 4) != 0) return; // check if discovery message
+
+	Serial.printf("New peer: " MACSTR "\n", MAC2STR(info->src_addr));
+	ESPNOWSerial *link = new ESPNOWSerial(info->src_addr, CHANNEL, WIFI_IF_AP);
+	link->begin();
+	link->setKey((const uint8_t *)key);
+	peers.push_back(link);
+}
+
+void setup() {
+	Serial.begin(115200);
+	WiFi.mode(WIFI_AP);
+	WiFi.setSleep(false);
+	WiFi.setChannel(CHANNEL);
+
+	ESP_NOW.onNewPeer(onNewPeer, NULL);
+	ESP_NOW.begin();
+
+	storage.begin("espnow-proxy");
+	if (!storage.isKey("key")) {
+		generateRandomKey();
+		storage.putString("key", key);
+	}
+	strcpy(key, storage.getString("key").c_str());
+
+	// Discover the first peer
+	while (peers.empty()) {
+		Serial.printf("espnow %s %s\n", WiFi.softAPmacAddress().c_str(), key);
+		delay(500);
+	}
+}
+
+void generateRandomKey() {
+	const char chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!@#$%^&*-_+=";
+	for (int i = 0; i < ESP_NOW_KEY_LEN; i++) {
+		key[i] = chars[random(0, strlen(chars))];
+	}
+}
+
+void loop() {
+	uint8_t buf[5000];
+
+	// Send from Serial to ESP-NOW
+	while (Serial.available() > 0) {
+		int b = Serial.read();
+		if (b < 0) {
+			break;
+		}
+
+		mavlink_message_t msg;
+		mavlink_status_t status;
+		if (mavlink_parse_char(MAVLINK_COMM_0, (uint8_t)b, &msg, &status)) {
+			int len = mavlink_msg_to_send_buffer(buf, &msg);
+			for (ESPNOWSerial *link : peers) {
+				link->write(buf, len);
+			}
+		}
+	}
+
+	// Send from ESP-NOW to Serial
+	for (ESPNOWSerial *link : peers) {
+		int len = link->read(buf, sizeof(buf));
+		if (len > 0) {
+			Serial.write(buf, len);
+		}
+	}
+}

tools/pyflix/README.md

@@ -37,7 +37,7 @@ 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.voltage)         # battery voltage (NaN - unknown, ~0 - USB powered)
 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]

tools/pyflix/flix.py

@@ -5,6 +5,7 @@
 
 import os
 import time
+import math
 from queue import Queue, Empty
 from typing import Optional, Callable, List, Dict, Any, Union, Sequence
 import logging
@@ -26,7 +27,7 @@ class Flix:
     mode: str = ''
     armed: bool = False
     landed: bool = False
-    voltage: float = 0
+    voltage: float = math.nan
     attitude: List[float]
     attitude_euler: List[float]  # roll, pitch, yaw
     rates: List[float]

tools/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "pyflix"
-version = "0.14"
+version = "0.15"
 description = "Python API for Flix drone"
 authors = [{ name="Oleg Kalachev", email="okalachev@gmail.com" }]
 license = "MIT"