Implement ESP-NOW support

tools/espnow-proxy/README.md

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+# ESPNOW-proxy
+
+Proxy sketch for using ESP-NOW MAVLink connection with Flix drone.

tools/espnow-proxy/espnow-proxy.ino

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+// Copyright (c) 2026 Oleg Kalachev <okalachev@gmail.com>
+// Repository: https://github.com/okalachev/flix
+
+// Proxy for ESP-NOW connection
+
+#include <WiFi.h>
+#include <ESP32_NOW_Serial.h>
+#include <MacAddress.h>
+#include <MAVLink.h>
+
+const int CHANNEL = 6;
+
+ESP_NOW_Serial_Class espnow(NULL, CHANNEL, WIFI_IF_AP);
+MacAddress peerMac;
+volatile bool peerFound = false;
+
+void onNewPeer(const esp_now_recv_info_t *info, const uint8_t *data, int len, void *arg) {
+	peerMac = info->src_addr;
+	peerFound = true;
+}
+
+void setup() {
+	Serial.begin(115200);
+	WiFi.mode(WIFI_AP);
+	WiFi.setSleep(false);
+	WiFi.setChannel(CHANNEL);
+
+	// while (!WiFi.AP.started()) {
+		// delay(100);
+	// }
+
+	ESP_NOW.onNewPeer(onNewPeer, NULL);
+	ESP_NOW.begin();
+
+	while (!peerFound) {
+		Serial.printf("MAC: %s, waiting for peer...\n", WiFi.softAPmacAddress().c_str());
+		delay(1000);
+	}
+	Serial.printf("Peer found: %s\n", peerMac.toString().c_str());
+
+	espnow.addr(peerMac);
+	espnow.setChannel(CHANNEL);
+	espnow.begin();
+}
+
+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);
+			// ESP_NOW.write(buf, len);
+			espnow.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));
+	if (len > 0) {
+		Serial.write(buf, len);
+	}
+}