ESP-NOW to mesh bridge

boards/esp32-s3-devkitc-1-myboard.json

@@ -0,0 +1,49 @@
+{
+  "build": {
+    "arduino":{
+      "ldscript": "esp32s3_out.ld",
+      "partitions": "elecrow_partitions.csv"
+    },
+    "core": "esp32",
+    "extra_flags": [
+      "-DARDUINO_USB_MODE=1",
+      "-DARDUINO_RUNNING_CORE=1",
+      "-DARDUINO_EVENT_RUNNING_CORE=1"
+    ],
+    "f_cpu": "240000000L",
+    "f_flash": "80000000L",
+    "flash_mode": "qio",
+    "hwids": [
+      [
+        "0x303A",
+        "0x1001"
+      ]
+    ],
+    "mcu": "esp32s3",
+    "variant": "esp32s3"
+  },
+  "connectivity": [
+    "wifi"
+  ],
+  "debug": {
+    "default_tool": "esp-builtin",
+    "onboard_tools": [
+      "esp-builtin"
+    ],
+    "openocd_target": "esp32s3.cfg"
+  },
+  "frameworks": [
+    "arduino",
+    "espidf"
+  ],
+  "name": "Espressif ESP32-S3-DevKitC-1-N8 -ELECROW",
+  "upload": {
+    "flash_size": "4MB",
+    "maximum_ram_size": 327680,
+    "maximum_size": 8388608,
+    "require_upload_port": true,
+    "speed": 921600
+  },
+  "url": "https://docs.espressif.com/projects/esp-idf/en/latest/esp32s3/hw-reference/esp32s3/user-guide-devkitc-1.html",
+  "vendor": "Espressif"
+}

elecrow_partitions.csv

@@ -0,0 +1,6 @@
+# Name,   Type, SubType, Offset,  Size, Flags
+nvs,      data, nvs,     0x9000,  0x5000,
+otadata,  data, ota,     0xe000,  0x2000,
+app0,     app,  ota_0,   0x10000, 0x300000,
+spiffs,   data, spiffs,  0x310000,0xE0000,
+coredump, data, coredump,0x3F0000,0x10000,

examples/simple_secure_chat/main.cpp

@@ -241,8 +241,10 @@ protected:
   }
 
   void onCommandDataRecv(const ContactInfo& from, mesh::Packet* pkt, uint32_t sender_timestamp, const char *text) override {
+    MESH_DEBUG_PRINTLN("onCommandDataRecv");
   }
   void onSignedMessageRecv(const ContactInfo& from, mesh::Packet* pkt, uint32_t sender_timestamp, const uint8_t *sender_prefix, const char *text) override {
+    MESH_DEBUG_PRINTLN("onSignedMessageRecv");
   }
 
   void onChannelMessageRecv(const mesh::GroupChannel& channel, mesh::Packet* pkt, uint32_t timestamp, const char *text) override {
@@ -255,10 +257,12 @@ protected:
   }
 
   uint8_t onContactRequest(const ContactInfo& contact, uint32_t sender_timestamp, const uint8_t* data, uint8_t len, uint8_t* reply) override {
+    MESH_DEBUG_PRINTLN("onContactRequest");
     return 0;  // unknown
   }
 
   void onContactResponse(const ContactInfo& contact, const uint8_t* data, uint8_t len) override {
+    MESH_DEBUG_PRINTLN("onContactResponse");
     // not supported
   }
 

src/helpers/esp32/ESPNOWRadio.cpp

@@ -3,12 +3,27 @@
 #include <WiFi.h>
 #include <esp_wifi.h>
 
+static constexpr uint16_t BRIDGE_PACKET_MAGIC = 0xC03E;
+static const size_t MAX_ESPNOW_PACKET_SIZE = 250;
+/**
+ * @brief Common field sizes used by bridge implementations
+ *
+ * These constants define the size of common packet fields used across bridges.
+ * BRIDGE_MAGIC_SIZE is used by all bridges for packet identification.
+ * BRIDGE_LENGTH_SIZE is used by bridges that need explicit length fields (like RS232).
+ * BRIDGE_CHECKSUM_SIZE is used by all bridges for Fletcher-16 checksums.
+ */
+static constexpr uint16_t BRIDGE_MAGIC_SIZE = sizeof(BRIDGE_PACKET_MAGIC);
+static constexpr uint16_t BRIDGE_LENGTH_SIZE = sizeof(uint16_t);
+static constexpr uint16_t BRIDGE_CHECKSUM_SIZE = sizeof(uint16_t);
+
 static uint8_t broadcastAddress[] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
 static esp_now_peer_info_t peerInfo;
 static volatile bool is_send_complete = false;
 static esp_err_t last_send_result;
 static uint8_t rx_buf[256];
 static uint8_t last_rx_len = 0;
+static char bridge_secret[16];
 
 // callback when data is sent
 static void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
@@ -16,15 +31,56 @@ static void OnDataSent(const uint8_t *mac_addr, esp_now_send_status_t status) {
   ESPNOW_DEBUG_PRINTLN("Send Status: %d", (int)status);
 }
 
+static void xorCrypt(uint8_t *data, size_t len) {
+  size_t keyLen = strlen(bridge_secret);
+  for (size_t i = 0; i < len; i++) {
+    data[i] ^= bridge_secret[i % keyLen];
+  }
+}
+
+static uint16_t fletcher16(const uint8_t *data, size_t len) {
+  uint8_t sum1 = 0, sum2 = 0;
+
+  for (size_t i = 0; i < len; i++) {
+    sum1 = (sum1 + data[i]) % 255;
+    sum2 = (sum2 + sum1) % 255;
+  }
+
+  return (sum2 << 8) | sum1;
+}
+
+static bool validateChecksum(const uint8_t *data, size_t len, uint16_t received_checksum) {
+  uint16_t calculated_checksum = fletcher16(data, len);
+  return received_checksum == calculated_checksum;
+}
+
 static void OnDataRecv(const uint8_t *mac, const uint8_t *data, int len) {
   ESPNOW_DEBUG_PRINTLN("Recv: len = %d", len);
-  memcpy(rx_buf, data, len);
-  last_rx_len = len;
+
+  if (len < 4) return;
+
+  uint16_t magic = (data[0] << 8) | data[1];
+  if (magic != BRIDGE_PACKET_MAGIC) return;
+
+  uint8_t decrypted[MAX_ESPNOW_PACKET_SIZE];
+  int encLen = len - 2; // everything except magic
+  memcpy(decrypted, data + 2, encLen);
+  xorCrypt(decrypted, encLen);
+
+  uint16_t rx_cksum = (decrypted[0] << 8) | decrypted[1];
+  uint8_t* meshPayload = decrypted + 2;
+  int meshLen = encLen - 2;
+
+  if (!validateChecksum(meshPayload, meshLen, rx_cksum)) return;
+
+  memcpy(rx_buf, meshPayload, meshLen);
+  last_rx_len = meshLen;
 }
 
 void ESPNOWRadio::init() {
   // Set device as a Wi-Fi Station
   WiFi.mode(WIFI_STA);
+  strncpy(bridge_secret, "LVSITANOS", sizeof(bridge_secret));
   // Long Range mode
   esp_wifi_set_protocol(WIFI_IF_STA, WIFI_PROTOCOL_LR);
 
@@ -72,7 +128,36 @@ uint32_t ESPNOWRadio::intID() {
 bool ESPNOWRadio::startSendRaw(const uint8_t* bytes, int len) {
   // Send message via ESP-NOW
   is_send_complete = false;
-  esp_err_t result = esp_now_send(broadcastAddress, bytes, len);
+  if (!bytes || len <= 0) {
+    Serial.println("Invalid raw mesh packet");
+    return false;
+  }
+
+  if (len > (MAX_ESPNOW_PACKET_SIZE - 4)) {
+    Serial.println("Mesh packet too large for ESP-NOW");
+    return false;
+  }
+
+  uint8_t out[MAX_ESPNOW_PACKET_SIZE];
+
+  // 1) magic
+  out[0] = (BRIDGE_PACKET_MAGIC >> 8) & 0xFF;
+  out[1] = BRIDGE_PACKET_MAGIC & 0xFF;
+
+  // 2) checksum (πάνω στο raw mesh packet)
+  uint16_t cksum = fletcher16(bytes, len);
+  out[2] = (cksum >> 8) & 0xFF;
+  out[3] = cksum & 0xFF;
+
+  // 3) payload = raw mesh packet
+  memcpy(out + 4, bytes, len);
+
+  // 4) encrypt checksum + payload
+  xorCrypt(out + 2, len + 2);
+
+  // 5) send via ESP-NOW
+  esp_err_t result = esp_now_send(broadcastAddress, out, len + 4);
+
   if (result == ESP_OK) {
     n_sent++;
     ESPNOW_DEBUG_PRINTLN("Send success");

variants/elecrow_espnow/platformio.ini

@@ -0,0 +1,31 @@
+; ----------- Elecrow Panels ESP32-S3 ------------
+; No LoRa module - Only ESP-NOW
+; Works with repeaters with esp_now
+[Elecrow_ESPNOW]
+extends = esp32_base
+board = esp32-s3-devkitc-1-myboard
+build_flags =
+  ${esp32_base.build_flags}
+  -I variants/Elecrow_espnow
+  -D PIN_BOARD_SDA=-1
+  -D PIN_BOARD_SCL=-1
+  -D PIN_USER_BTN=0
+;  -D ESPNOW_DEBUG_LOGGING=1
+;  -D MESH_PACKET_LOGGING=1
+;  -D MESH_DEBUG=1
+build_src_filter = ${esp32_base.build_src_filter}
+  +<helpers/esp32/ESPNOWRadio.cpp>
+  +<../variants/Elecrow_espnow>
+
+[env:Elecrow_ESPNOW_terminal_chat]
+extends = Elecrow_ESPNOW
+build_flags =
+  ${Elecrow_ESPNOW.build_flags}
+  -D MAX_CONTACTS=350
+  -D MAX_GROUP_CHANNELS=8
+  -D MESH_DEBUG=1
+build_src_filter = ${Elecrow_ESPNOW.build_src_filter}
+  +<../examples/simple_secure_chat/main.cpp>
+lib_deps =
+  ${Elecrow_ESPNOW.lib_deps}
+  densaugeo/base64 @ ~1.4.0

variants/elecrow_espnow/target.cpp

@@ -0,0 +1,44 @@
+#include <Arduino.h>
+#include "target.h"
+#include <helpers/ArduinoHelpers.h>
+
+ESP32Board board;
+
+ESPNOWRadio radio_driver;
+
+ESP32RTCClock rtc_clock;
+SensorManager sensors;
+
+bool radio_init() {
+  rtc_clock.begin();
+
+  radio_driver.init();
+
+  return true;  // success
+}
+
+uint32_t radio_get_rng_seed() {
+  return millis() + radio_driver.intID();  // TODO: where to get some entropy?
+}
+
+void radio_set_params(float freq, float bw, uint8_t sf, uint8_t cr) {
+  // no-op
+}
+
+void radio_set_tx_power(uint8_t dbm) {
+  radio_driver.setTxPower(dbm);
+}
+
+// NOTE: as we are using the WiFi radio, the ESP_IDF will have enabled hardware RNG:
+//    https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/system/random.html
+class ESP_RNG : public mesh::RNG {
+public:
+  void random(uint8_t* dest, size_t sz) override {
+    esp_fill_random(dest, sz);
+  }
+};
+
+mesh::LocalIdentity radio_new_identity() {
+  ESP_RNG rng;
+  return mesh::LocalIdentity(&rng);  // create new random identity
+}

variants/elecrow_espnow/target.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <helpers/ESP32Board.h>
+#include <helpers/esp32/ESPNOWRadio.h>
+#include <helpers/SensorManager.h>
+
+extern ESP32Board board;
+extern ESPNOWRadio radio_driver;
+extern ESP32RTCClock rtc_clock;
+extern SensorManager sensors;
+
+bool radio_init();
+uint32_t radio_get_rng_seed();
+void radio_set_params(float freq, float bw, uint8_t sf, uint8_t cr);
+void radio_set_tx_power(uint8_t dbm);
+mesh::LocalIdentity radio_new_identity();

variants/generic-e22/variant.h

@@ -19,7 +19,7 @@
 // Radio
 #define USE_SX1262 // E22-900M30S uses SX1262
 #define USE_SX1268 // E22-400M30S uses SX1268
-#define SX126X_MAX_POWER 22 // Outputting 22dBm from SX1262 results in ~30dBm E22-900M30S output (module only uses last stage of the YP2233W PA)
+#define SX126X_MAX_POWER 27 // Outputting 22dBm from SX1262 results in ~30dBm E22-900M30S output (module only uses last stage of the YP2233W PA)
 #define SX126X_DIO3_TCXO_VOLTAGE 1.8 // E22 series TCXO reference voltage is 1.8V
 
 #define SX126X_CS 18    // EBYTE module's NSS pin

variants/heltec_v4/platformio.ini

@@ -26,7 +26,7 @@ build_flags =
   -D PIN_VEXT_EN=36
   -D PIN_VEXT_EN_ACTIVE=HIGH
   -D LORA_TX_POWER=10 ;If it is configured as 10 here, the final output will be 22 dbm.
-  -D MAX_LORA_TX_POWER=22 ; Max SX1262 output
+  -D MAX_LORA_TX_POWER=27 ; Max SX1262 output
   -D SX126X_DIO2_AS_RF_SWITCH=true
   -D SX126X_DIO3_TCXO_VOLTAGE=1.8
   -D SX126X_CURRENT_LIMIT=140

variants/meshadventurer/variant.h

@@ -19,7 +19,7 @@
 // Radio
 #define USE_SX1262 // E22-900M30S uses SX1262
 #define USE_SX1268 // E22-400M30S uses SX1268
-#define SX126X_MAX_POWER 22 // Outputting 22dBm from SX1262 results in ~30dBm E22-900M30S output (module only uses last stage of the YP2233W PA)
+#define SX126X_MAX_POWER 27 // Outputting 22dBm from SX1262 results in ~30dBm E22-900M30S output (module only uses last stage of the YP2233W PA)
 #define SX126X_DIO3_TCXO_VOLTAGE 1.8 // E22 series TCXO reference voltage is 1.8V
 
 #define SX126X_CS 18    // EBYTE module's NSS pin