Test failing simulator run

Add missing extern variables.
Fix warning.

.github/workflows/build.yml

@@ -76,6 +76,11 @@ jobs:
       run: sudo apt-get install -y libsdl2-dev
     - name: Build simulator
       run: make build_simulator
+    - name: Run simulator
+      env:
+        GAZEBO_MODEL_PATH: ${{ github.workspace }}/gazebo/models
+        GAZEBO_PLUGIN_PATH: ${{ github.workspace }}/gazebo/build
+      run: timeout --preserve-status 120 gzserver --verbose gazebo/flix.world || [ $? -eq 143 ]
     - uses: actions/upload-artifact@v4
       with:
         name: gazebo-plugin-binary

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.
+* Communication using MAVLink protocol over Wi-Fi or ESP-NOW.
-* Control using USB gamepad, remote control or smartphone.
+* 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.
@@ -47,6 +47,14 @@ See the [user builds gallery](docs/user.md):
 
 <a href="docs/user.md"><img src="docs/img/user/user.jpg" width=500></a>
 
+### PCB
+
+The official PCB *(Flix2)* is in development now. Follow the [project's channel](https://t.me/opensourcequadcopter) to track the progress.
+
+Outdoor flights demo video of the current prototype:
+
+<a href="https://youtu.be/KXlNmvUTi4g"><img width=300 src="https://i3.ytimg.com/vi/KXlNmvUTi4g/maxresdefault.jpg"></a>
+
 ## Simulation
 
 The simulator is implemented using Gazebo and runs the original Arduino code:
@@ -73,7 +81,7 @@ Additional articles:
 |-|-|:-:|:-:|
 |Microcontroller board|ESP32 Mini.<br>ESP32-S3/ESP32-C3 boards are also supported.|<img src="docs/img/esp32.jpg" width=100>|1|
 |IMU (and barometer¹) board|GY‑91, MPU-9265 (or other MPU‑9250/MPU‑6500 board)<br>ICM20948V2 (ICM‑20948)<br>GY-521 (MPU-6050)|<img src="docs/img/gy-91.jpg" width=90 align=center><br><img src="docs/img/icm-20948.jpg" width=100><br><img src="docs/img/gy-521.jpg" width=100>|1|
-|Boost converter (optional, for more stable power supply)|5V output|<img src="docs/img/buck-boost.jpg" width=100>|1|
+|*Boost converter (optional, for more stable power supply)*|*5V output*|<img src="docs/img/buck-boost.jpg" width=100>|1|
 |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 or 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|

docs/troubleshooting.md

@@ -5,7 +5,7 @@
 Do the following:
 
 * **Check ESP32 core is installed**. Check if the version matches the one used in the [tutorial](usage.md#building-the-firmware).
-* **Check libraries**. Install all the required libraries from the tutorial. Make sure there are no MPU9250 or other peripherals libraries that may conflict with the ones used in the tutorial.
+* **Check libraries**. Install all the required libraries from the tutorial. Make sure there are no MPU-9250 or other peripherals libraries that may conflict with the ones used in the tutorial.
 * **Check the chosen board**. The correct board to choose in Arduino IDE for ESP32 Mini is *WEMOS D1 MINI ESP32*.
 
 ## The drone doesn't fly

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.
+* `2` — Client mode *(STA)* — the drone connects to an existing Wi-Fi network (may cause additional delays, so generally not recommended).
-* `3` — *ESP-NOW (not implemented yet)*.
+* `3` — ESP-NOW mode — the drone uses ESP-NOW protocol for communication.
-
-> [!WARNING]
-> Tests showed that Client mode may cause **additional delays** in remote control (due to retranslations), so it's generally not recommended.
 
 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. [The maximum number](https://github.com/espressif/esp-idf/blob/e95cab4be8fd293e3f3323181e7a2280874da6f7/components/esp_wifi/include/esp_now.h#L32-L33) of simultaneously connected drones is 20 (unencrypted) io 6 (encrypted).
+
+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.ino

@@ -10,6 +10,7 @@
 
 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 +46,7 @@ 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"
@@ -143,9 +145,11 @@ 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/mavlink.ino

@@ -41,7 +41,7 @@ void sendMavlink() {
 			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 voltages[] = {(uint16_t)(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,
@@ -241,7 +241,7 @@ void handleMavlink(const void *_msg) {
 		}
 
 		if (m.command == MAV_CMD_COMPONENT_ARM_DISARM) {
-			if (m.param1 && controlThrottle > 0.05) return; // don't arm if throttle is not low
+			if (m.param1 == 1 && controlThrottle > 0.05) return; // don't arm if throttle is not low
 			accepted = true;
 			armed = m.param1 == 1;
 		}

flix/motors.ino

@@ -14,10 +14,7 @@ int pwmStop = 0;
 int pwmMin = 0;
 int pwmMax = -1; // -1 means duty cycle mode
 
-const int MOTOR_REAR_LEFT = 0;
+const int MOTOR_REAR_LEFT = 0, MOTOR_REAR_RIGHT = 1, MOTOR_FRONT_RIGHT = 2, MOTOR_FRONT_LEFT = 3;
-const int MOTOR_REAR_RIGHT = 1;
-const int MOTOR_FRONT_RIGHT = 2;
-const int MOTOR_FRONT_LEFT = 3;
 
 void setupMotors() {
 	print("Setup Motors\n");

flix/parameters.ino

@@ -6,13 +6,11 @@
 #include <Preferences.h>
 #include "util.h"
 
-extern int channelZero[16];
+extern int channelZero[16], channelMax[16];
-extern int channelMax[16];
 extern int rollChannel, pitchChannel, throttleChannel, yawChannel, armedChannel, modeChannel;
-extern int rcRxPin;
+extern int rcRxPin, voltagePin;
-extern int wifiMode, udpLocalPort, udpRemotePort;
+extern int wifiMode, wifiLongRange, udpLocalPort, udpRemotePort, espnowChannel;
 extern float rcLossTimeout, descendTime;
-extern int voltagePin;
 extern float voltageScale;
 extern LowPassFilter<float> voltageFilter;
 
@@ -112,6 +110,9 @@ 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},

flix/util.h

@@ -6,6 +6,7 @@
 #pragma once
 
 #include <math.h>
+#include <ESP32_NOW_Serial.h>
 
 const float ONE_G = 9.80665;
 extern float t;
@@ -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/wifi.ino

@@ -1,82 +1,133 @@
 // Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
 // Repository: https://github.com/okalachev/flix
 
-// Wi-Fi communication
+// Wi-Fi and ESP-NOW communication
 
 #include <WiFi.h>
 #include <WiFiAP.h>
 #include <WiFiUdp.h>
-#include "Preferences.h"
+#include <MacAddress.h>
+#include <ESP32_NOW_Serial.h>
+#include <Preferences.h>
+#include "util.h"
 
 extern Preferences storage; // use the main preferences storage
 
-const int W_DISABLED = 0, W_AP = 1, W_STA = 2;
+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;
 IPAddress udpRemoteIP = "255.255.255.255";
-
 WiFiUDP udp;
 
+ESPNOWSerial espnow(NULL, 0, WIFI_IF_AP);
+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());
-	} 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);
+	}
+
+	if (wifiMode == W_STA) {
+		WiFi.begin(storage.getString("WIFI_STA_SSID", "").c_str(), storage.getString("WIFI_STA_PASS", "").c_str());
+		udp.begin(udpLocalPort);
+	}
+
+	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 (WiFi.getMode() == WIFI_MODE_AP) {
+	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("IP: %s\n", WiFi.localIP().toString().c_str());
+		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");
-		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) {
+void configWiFi(int mode, const char *first, const char *second) {
-	if (ap) {
+	MacAddress mac;
-		storage.putString("WIFI_AP_SSID", ssid);
+	if (mode == W_AP && strlen(first) > 0 && strlen(second) >= 8) {
-		storage.putString("WIFI_AP_PASS", password);
+		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 {
-		storage.putString("WIFI_STA_SSID", ssid);
+		print("Invalid configuration\n");
-		storage.putString("WIFI_STA_PASS", password);
+		return;
 	}
 	print("✓ Reboot to apply new settings\n");
 }

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/wifi.h

@@ -11,7 +11,12 @@
 #include <sys/poll.h>
 #include <gazebo/gazebo.hh>
 
-int wifiMode = 1; // mock
+// Mocks
+int wifiMode = 1;
+int wifiLongRange = 0;
+// int espnowChannel = 6;
+const int W_DISABLED = 0, W_AP = 1, W_STA = 2, W_ESPNOW = 3;
+
 int udpLocalPort = 14580;
 int udpRemotePort = 14550;
 const char *udpRemoteIP = "255.255.255.255";

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);
+		}
+	}
+}