Improve ESP-NOW connection

Implement auto-pairing.
Make key optional.
Remove re-sends.
Add command for uploading proxy to makefile.

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 ..

flix/cli.ino

@@ -46,7 +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> - setup ESP-NOW peer\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"

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

@@ -9,19 +9,22 @@
 #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, W_ESPNOW = 3;
 int wifiMode = W_AP;
+
 int wifiLongRange = 0;
 int udpLocalPort = 14550;
 int udpRemotePort = 14550;
-int espnowChannel = 6;
 IPAddress udpRemoteIP = "255.255.255.255";
-
 WiFiUDP udp;
-ESP_NOW_Serial_Class espnow(NULL, 0, WIFI_IF_AP);
+
+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");
@@ -37,8 +40,12 @@ void setupWiFi() {
 		WiFi.mode(WIFI_AP);
 		WiFi.setChannel(espnowChannel);
 		espnow.setChannel(espnowChannel);
-		espnow.addr(MacAddress(storage.getString("ESPNOW_PEER_MAC", "").c_str()));
+		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.setChannel(espnowChannel);
+		espnowBroadcast.begin();
 	}
 
 	WiFi.setSleep(false); // disable power save
@@ -47,6 +54,8 @@ void setupWiFi() {
 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;
 	}
 
@@ -76,6 +85,7 @@ void printWiFiInfo() {
 		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");
@@ -103,14 +113,19 @@ void printWiFiInfo() {
 }
 
 void configWiFi(int mode, const char *first, const char *second) {
-	if (mode == W_AP) {
+	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) {
+	} 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) {
+	} 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");
 }

tools/espnow-proxy/espnow-proxy.ino

@@ -7,16 +7,25 @@
 #include <ESP32_NOW_Serial.h>
 #include <MacAddress.h>
 #include <MAVLink.h>
+#include <Preferences.h>
+#include "../../flix/util.h"
+#include <vector>
 
 const int CHANNEL = 6;
+char key[ESP_NOW_KEY_LEN + 1] = {0}; // with trailing null
 
-ESP_NOW_Serial_Class espnow(NULL, CHANNEL, WIFI_IF_AP);
+Preferences storage;
-MacAddress peerMac;
+
-volatile bool peerFound = false;
+std::vector<ESPNOWSerial *> peers;
 
 void onNewPeer(const esp_now_recv_info_t *info, const uint8_t *data, int len, void *arg) {
-	peerMac = info->src_addr;
+	if (len != 4 || memcmp(data, "flix", 4) != 0) return; // check if discovery message
-	peerFound = true;
+
+	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() {
@@ -25,22 +34,28 @@ void setup() {
 	WiFi.setSleep(false);
 	WiFi.setChannel(CHANNEL);
 
-	// while (!WiFi.AP.started()) {
-		// delay(100);
-	// }
-
 	ESP_NOW.onNewPeer(onNewPeer, NULL);
 	ESP_NOW.begin();
 
-	while (!peerFound) {
+	storage.begin("espnow-proxy");
-		Serial.printf("MAC: %s, waiting for peer...\n", WiFi.softAPmacAddress().c_str());
+	if (!storage.isKey("key")) {
-		delay(1000);
+		generateRandomKey();
+		storage.putString("key", key);
 	}
-	Serial.printf("Peer found: %s\n", peerMac.toString().c_str());
+	strcpy(key, storage.getString("key").c_str());
 
-	espnow.addr(peerMac);
+	// Discover the first peer
-	espnow.setChannel(CHANNEL);
+	while (peers.empty()) {
-	espnow.begin();
+		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() {
@@ -57,16 +72,17 @@ void loop() {
 		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);
-			// ESP_NOW.write(buf, len);
+			for (ESPNOWSerial *link : peers) {
-			espnow.write(buf, len);
+				link->write(buf, len);
-			// espnow.send(buf, len);
+			}
-			// esp_now_send(peerMac, buf, len);
 		}
 	}
 
 	// Send from ESP-NOW to serial
-	int len = espnow.read(buf, sizeof(buf));
+	for (ESPNOWSerial *link : peers) {
-	if (len > 0) {
+		int len = link->read(buf, sizeof(buf));
-		Serial.write(buf, len);
+		if (len > 0) {
+			Serial.write(buf, len);
+		}
 	}
 }