Meshtastic BLE Protocol

About Meshtastic Communication Protocol With BLE To Mobile. Source Doc

以下有經過Claude AI協助解釋，可能會有不正確的內容，還請見諒。

• Meshtastic BLE Protocol
• BLE Services
• Code
  • NimbleBluetooth.cpp
  • PhoneAPI.cpp
• Protobuf Struct
  • Code Generate
    • Python
    • C#
    • C++
  • MeshPacket
  • FromRadio
  • ToRadio
• Raw Message
  • Print Code
  • ToRadioCharacteristic
• Reference

BLE Services

• Mesh Service
  • UUID: 6ba1b218-15a8-461f-9fa8-5dcae273eafd
  • Characterstatic:
    • ToRadioCharacteristic
      • UUID: f75c76d2-129e-4dad-a1dd-7866124401e7
      • Property: Write
    • FromRadioCharacteristic
      • UUID: 2c55e69e-4993-11ed-b878-0242ac120002
      • Property: Read
    • fromNumCharacteristic
      • UUID: ed9da18c-a800-4f66-a670-aa7547e34453
      • Property: Read / Notify
• Battery Service
  • UUID: 0x2a19
  • Characterstatic:
    • BatteryCharacteristic: 電池%數
      • UUID: 0x2A19
      • Property: Read / Notify
      • Descriptor:
        • UUID: 0x2904
        • Format: UInt8
        • Namespace: 1
        • Unit: 0x27AD (Percentage)

Code

NimbleBluetooth.cpp

• NimbleBluetoothToRadioCallback::onWrite()：負責處理藍牙通訊的 ToRadio Services。當該特性值發生變化時，會觸發此Callback。 (ID: f75c76d2-129e-4dad-a1dd-7866124401e7)
  1. 記錄一個 "To Radio onwrite" 的 log 訊息。
  ​LOG_INFO("To Radio onwrite\n");
  

  2. 獲取藍牙特性的值 (pCharacteristic->getValue())。
  ​​​​auto val = pCharacteristic->getValue();
  

  3. 調用 bluetoothPhoneAPI->handleToRadio() 函數，將獲取到的藍牙特性值傳遞過去。
  ​​​​bluetoothPhoneAPI->handleToRadio(val.data()， val.length());
  

• NimbleBluetoothFromRadioCallback::onRead()：負責處理藍牙通訊的 FromRadio Services。當手機讀取此特性值時，會觸發此Callback。 (ID: 2c55e69e-4993-11ed-b878-0242ac120002)
  1. 記錄一個 "From Radio onread" 的 log 訊息。
  ​LOG_INFO("From Radio onread\n");
  

  2. 定義一個大小為 meshtastic_FromRadio_size 的Buffer fromRadioBytes。並調用 bluetoothPhoneAPI->getFromRadio() 函數，將無線電設備發送的資料拷貝到 fromRadioBytes Buffer，並獲取實際拷貝的字節數 numBytes。
  ​uint8_t fromRadioBytes[meshtastic_FromRadio_size];
  ​size_t numBytes = bluetoothPhoneAPI->getFromRadio(fromRadioBytes);
  

  3. 使用 fromRadioBytes Buffer資料，宣告字串 fromRadioByteString，並將 fromRadioByteString 寫入到藍牙 FromRadio 特性值中，以便讓手機或其他支援BLE的程式讀取。
  ​std::string fromRadioByteString(fromRadioBytes， fromRadioBytes + numBytes);
  ​pCharacteristic->setValue(fromRadioByteString);
  

PhoneAPI.cpp

• PhoneAPI::handleToRadio()：處理從手機向無線電發送的 ToRadio 協定訊息。
  1. 當手機與無線電設備 (ESP32) 保持通訊時， 觸發EVENT_CONTACT_FROM_PHONE， 以防止無線電設備 (ESP32) 進入睡眠模式。
  ​​​​powerFSM.trigger(EVENT_CONTACT_FROM_PHONE); // As long as the phone keeps talking to us， don't let the radio go to sleep
  

  2. 將接收到的 ToRadio 訊息解碼到 toRadioScratch 結構體中。
  ​​​​pb_decode_from_bytes(buf， bufLength， &meshtastic_ToRadio_msg， &toRadioScratch);
  

  3. 依據 toRadioScratch 中的 which_payload_variant 欄位，分別處理不同類型的 ToRadio 訊息:
     • meshtastic_ToRadio_packet_tag: 呼叫 handleToRadioPacket() 函數處理封包。
     ​​​​​​​case meshtastic_ToRadio_packet_tag:
     ​​​​​​​ return handleToRadioPacket(toRadioScratch.packet);
     

     • meshtastic_ToRadio_want_config_id_tag: 取得設定檔 ID (config_nonce)，並呼叫 handleStartConfig() 函數。
     ​​​​​​​case meshtastic_ToRadio_want_config_id_tag:
     ​​​​​​​ config_nonce = toRadioScratch.want_config_id;
     ​​​​​​​ LOG_INFO("Client wants config， nonce=%u\n"， config_nonce);
     ​​​​​​​ handleStartConfig();
     ​​​​​​​ break;
     

     • meshtastic_ToRadio_disconnect_tag: 關閉與手機的連接。
     ​​​​​​​case meshtastic_ToRadio_disconnect_tag:
     ​​​​​​​ LOG_INFO("Disconnecting from phone\n");
     ​​​​​​​ close();
     ​​​​​​​ break;
     

     • meshtastic_ToRadio_xmodemPacket_tag: 呼叫 xModem.handlePacket() 處理 xmodem 封包。
     • 或許是更新韌體的地方 (2024.4.13 blackcat)
     ​​​​​​​case meshtastic_ToRadio_xmodemPacket_tag:
     ​​​​​​​ LOG_INFO("Got xmodem packet\n");
     ​​​​​​​ xModem.handlePacket(toRadioScratch.xmodemPacket);
     ​​​​​​​ break;
     

     • meshtastic_ToRadio_mqttClientProxyMessage_tag: 呼叫 mqtt->onClientProxyReceive() 處理 MQTT 代理訊息。
     • 若 MQTT 代理沒有啟用，此Function無效。
     ​​​​​​​#if !MESHTASTIC_EXCLUDE_MQTT
     ​​​​​​​case meshtastic_ToRadio_mqttClientProxyMessage_tag:
     ​​​​​​​ LOG_INFO("Got MqttClientProxy message\n");
     ​​​​​​​ if (mqtt && moduleConfig.mqtt.proxy_to_client_enabled && moduleConfig.mqtt.enabled &&
     ​​​​​​​     (channels.anyMqttEnabled() || moduleConfig.mqtt.map_reporting_enabled)) {
     ​​​​​​​     mqtt->onClientProxyReceive(toRadioScratch.mqttClientProxyMessage);
     ​​​​​​​ } else {
     ​​​​​​​     LOG_WARN("MqttClientProxy received but proxy is not enabled， no channels have up/downlink， or map reporting "
     ​​​​​​​                 "not enabled\n");
     ​​​​​​​ }
     ​​​​​​​ break;
     ​​​​​​​#endif
     

     • meshtastic_ToRadio_heartbeat_tag: 記錄已收到手機的心跳訊號。
     ​​​​​​​case meshtastic_ToRadio_heartbeat_tag:
     ​​​​​​​  LOG_DEBUG("Got client heartbeat\n");
     ​​​​​​​  break;
     

  4. 如果無法解碼 ToRadio 訊息，會記錄錯誤訊息。
  ​​​​LOG_ERROR("Error: ignoring malformed toradio\n");
  

• PhoneAPI::getFromRadio()：處理從無線電向手機發送的 FromRadio 協定訊息。
  1. 根據當前的狀態 (state 變數)，對應不同的訊息類型進行處理。
     • STATE_SEND_MY_INFO：發送個人資訊。
     • STATE_SEND_METADATA：發送設備 (這裡指無線電) 的原始資料。
     • STATE_SEND_NODEINFO：發送節點資訊。
     • STATE_SEND_CHANNELS：發送頻道配置。
     • STATE_SEND_CONFIG：發送設備 (這裡指無線電) 設定資訊。
       • meshtastic_Config_device_tag：裝置資訊
       • meshtastic_Config_position_tag：GPS定位
       • meshtastic_Config_power_tag：省電
       • meshtastic_Config_network_tag：WiFi網路
       • meshtastic_Config_display_tag：螢幕 (如SSD1306 / SSD1308…等)
       • meshtastic_Config_lora_tag：LoRa模組 (如SX1262 / 1276 / 1278…等)
       • meshtastic_Config_bluetooth_tag：藍芽
     • STATE_SEND_MODULECONFIG：發送功能模組的設定資訊。
       • meshtastic_ModuleConfig_mqtt_tag：MQTT網路
       • meshtastic_ModuleConfig_serial_tag：序列埠 (如TTL / RS232…等)
       • meshtastic_ModuleConfig_external_notification_tag：外部裝置輸出 (如LED / 蜂鳴器…等)
       • meshtastic_ModuleConfig_store_forward_tag：告訴路由節點暫時存儲 / 轉發訊息給其他裝置
         • 這裡需要再修一下 (2024.4.13 blackcat)
       • meshtastic_ModuleConfig_range_test_tag：兩節點之間的距離測試
       • meshtastic_ModuleConfig_telemetry_tag：遙測模組 (如BME280、SHT31…等 Sensor)
       • meshtastic_ModuleConfig_canned_message_tag：事先設定好預發送的訊息
       • meshtastic_ModuleConfig_audio_tag：音頻資料
       • meshtastic_ModuleConfig_remote_hardware_tag：遙控其他節點的GPIO開/關
       • meshtastic_ModuleConfig_neighbor_info_tag：鄰近節點的資訊
       • meshtastic_ModuleConfig_detection_sensor_tag：開關 / 壓力感測器 / 紅外線感測器 (輸出訊號為Low或者High)
       • meshtastic_ModuleConfig_ambient_lighting_tag：漸變燈 / 呼吸燈
       • meshtastic_ModuleConfig_paxcounter_tag：透過WiFi或者藍芽 MAC位置計算該周圍的人數
     • STATE_SEND_COMPLETE_ID：發送設定完成的標識。
     • STATE_SEND_PACKETS：發送從Mesh網路接收的封包。
  2. 將要發送的資訊打包成 FromRadio 格式,並返回實際寫入Buffer的字節數。
  ​// Do we have a message from the mesh?
  ​​​​if (fromRadioScratch.which_payload_variant != 0) {
  ​​​​    // Encapsulate as a FromRadio packet
  ​​​​    size_t numbytes = pb_encode_to_bytes(buf, meshtastic_FromRadio_size, &meshtastic_FromRadio_msg, &fromRadioScratch);
  
  ​​​​    LOG_DEBUG("encoding toPhone packet to phone variant=%d, %d bytes\n", fromRadioScratch.which_payload_variant, numbytes);
  ​​​​    return numbytes;
  ​​​​}
  

Protobuf Struct

Code Generate

• 可以用meshtastic專案的bat，也可以用這裡的檔案。
  • 環境變數：<Top Folder>\protoc\bin

Python

protoc.exe --python_out=out -I=../protobufs ../protobufs/meshtastic/*.proto

C#

protoc.exe --csharp_out=out --proto_path=../protobufs ../protobufs/meshtastic/*.proto

C++

• meshtastic專案資料夾/bin/regen-protos.bat

protoc.exe --experimental_allow_proto3_optional "--nanopb_out=-S.cpp -v:out\" -I=..\protobufs ..\protobufs\meshtastic\*.proto

MeshPacket

message MeshPacket {
  /*
   * The priority of this message for sending.
   * Higher priorities are sent first (when managing the transmit queue).
   * This field is never sent over the air, it is only used internally inside of a local device node.
   * API clients (either on the local node or connected directly to the node)
   * can set this parameter if necessary.
   * (values must be <= 127 to keep protobuf field to one byte in size.
   * Detailed background on this field:
   * I noticed a funny side effect of lora being so slow: Usually when making
   * a protocol there isn’t much need to use message priority to change the order
   * of transmission (because interfaces are fairly fast).
   * But for lora where packets can take a few seconds each, it is very important
   * to make sure that critical packets are sent ASAP.
   * In the case of meshtastic that means we want to send protocol acks as soon as possible
   * (to prevent unneeded retransmissions), we want routing messages to be sent next,
   * then messages marked as reliable and finally 'background' packets like periodic position updates.
   * So I bit the bullet and implemented a new (internal - not sent over the air)
   * field in MeshPacket called 'priority'.
   * And the transmission queue in the router object is now a priority queue.
   */
  enum Priority {
    /*
     * Treated as Priority.DEFAULT
     */
    UNSET = 0;
    /*
     * TODO: REPLACE
     */
    MIN = 1;
    /*
     * Background position updates are sent with very low priority -
     * if the link is super congested they might not go out at all
     */
    BACKGROUND = 10;
    /*
     * This priority is used for most messages that don't have a priority set
     */
    DEFAULT = 64;
    /*
     * If priority is unset but the message is marked as want_ack,
     * assume it is important and use a slightly higher priority
     */
    RELIABLE = 70;
    /*
     * Ack/naks are sent with very high priority to ensure that retransmission
     * stops as soon as possible
     */
    ACK = 120;
    /*
     * TODO: REPLACE
     */
    MAX = 127;
  }
  /*
   * Identify if this is a delayed packet
   */
  enum Delayed {
    /*
     * If unset, the message is being sent in real time.
     */
    NO_DELAY = 0;
    /*
     * The message is delayed and was originally a broadcast
     */
    DELAYED_BROADCAST = 1;
    /*
     * The message is delayed and was originally a direct message
     */
    DELAYED_DIRECT = 2;
  }
  /*
   * The sending node number.
   * Note: Our crypto implementation uses this field as well.
   * See [crypto](/docs/overview/encryption) for details.
   */
  fixed32 from = 1;
  /*
   * The (immediate) destination for this packet
   */
  fixed32 to = 2;
  /*
   * (Usually) If set, this indicates the index in the secondary_channels table that this packet was sent/received on.
   * If unset, packet was on the primary channel.
   * A particular node might know only a subset of channels in use on the mesh.
   * Therefore channel_index is inherently a local concept and meaningless to send between nodes.
   * Very briefly, while sending and receiving deep inside the device Router code, this field instead
   * contains the 'channel hash' instead of the index.
   * This 'trick' is only used while the payload_variant is an 'encrypted'.
   */
  uint32 channel = 3;
  /*
   * Internally to the mesh radios we will route SubPackets encrypted per [this](docs/developers/firmware/encryption).
   * However, when a particular node has the correct
   * key to decode a particular packet, it will decode the payload into a SubPacket protobuf structure.
   * Software outside of the device nodes will never encounter a packet where
   * "decoded" is not populated (i.e. any encryption/decryption happens before reaching the applications)
   * The numeric IDs for these fields were selected to keep backwards compatibility with old applications.
   */
  oneof payload_variant {
    /*
     * TODO: REPLACE
     */
    Data decoded = 4;
    /*
     * TODO: REPLACE
     */
    bytes encrypted = 5;
  }
  /*
   * A unique ID for this packet.
   * Always 0 for no-ack packets or non broadcast packets (and therefore take zero bytes of space).
   * Otherwise a unique ID for this packet, useful for flooding algorithms.
   * ID only needs to be unique on a _per sender_ basis, and it only
   * needs to be unique for a few minutes (long enough to last for the length of
   * any ACK or the completion of a mesh broadcast flood).
   * Note: Our crypto implementation uses this id as well.
   * See [crypto](/docs/overview/encryption) for details.
   */
  fixed32 id = 6;
  /*
   * The time this message was received by the esp32 (secs since 1970).
   * Note: this field is _never_ sent on the radio link itself (to save space) Times
   * are typically not sent over the mesh, but they will be added to any Packet
   * (chain of SubPacket) sent to the phone (so the phone can know exact time of reception)
   */
  fixed32 rx_time = 7;
  /*
   * *Never* sent over the radio links.
   * Set during reception to indicate the SNR of this packet.
   * Used to collect statistics on current link quality.
   */
  float rx_snr = 8;
  /*
   * If unset treated as zero (no forwarding, send to adjacent nodes only)
   * if 1, allow hopping through one node, etc...
   * For our usecase real world topologies probably have a max of about 3.
   * This field is normally placed into a few of bits in the header.
   */
  uint32 hop_limit = 9;
  /*
   * This packet is being sent as a reliable message, we would prefer it to arrive at the destination.
   * We would like to receive a ack packet in response.
   * Broadcasts messages treat this flag specially: Since acks for broadcasts would
   * rapidly flood the channel, the normal ack behavior is suppressed.
   * Instead, the original sender listens to see if at least one node is rebroadcasting this packet (because naive flooding algorithm).
   * If it hears that the odds (given typical LoRa topologies) the odds are very high that every node should eventually receive the message.
   * So FloodingRouter.cpp generates an implicit ack which is delivered to the original sender.
   * If after some time we don't hear anyone rebroadcast our packet, we will timeout and retransmit, using the regular resend logic.
   * Note: This flag is normally sent in a flag bit in the header when sent over the wire
   */
  bool want_ack = 10;
  /*
   * The priority of this message for sending.
   * See MeshPacket.Priority description for more details.
   */
  Priority priority = 11;
  /*
   * rssi of received packet. Only sent to phone for dispay purposes.
   */
  int32 rx_rssi = 12;
  /*
   * Describe if this message is delayed
   */
  Delayed delayed = 13 [deprecated = true];
  /*
   * Describes whether this packet passed via MQTT somewhere along the path it currently took.
   */
  bool via_mqtt = 14;
  /*
   * Hop limit with which the original packet started. Sent via LoRa using three bits in the unencrypted header.
   * When receiving a packet, the difference between hop_start and hop_limit gives how many hops it traveled.
   */
  uint32 hop_start = 15;
}

FromRadio

message FromRadio {
  /*
   * The packet id, used to allow the phone to request missing read packets from the FIFO,
   * see our bluetooth docs
   */
  uint32 id = 1;
  /*
   * Log levels, chosen to match python logging conventions.
   */
  oneof payload_variant {
    /*
     * Log levels, chosen to match python logging conventions.
     */
    MeshPacket packet = 2;
    /*
     * Tells the phone what our node number is, can be -1 if we've not yet joined a mesh.
     * NOTE: This ID must not change - to keep (minimal) compatibility with <1.2 version of android apps.
     */
    MyNodeInfo my_info = 3;
    /*
     * One packet is sent for each node in the on radio DB
     * starts over with the first node in our DB
     */
    NodeInfo node_info = 4;
    /*
     * Include a part of the config (was: RadioConfig radio)
     */
    Config config = 5;
    /*
     * Set to send debug console output over our protobuf stream
     */
    LogRecord log_record = 6;
    /*
     * Sent as true once the device has finished sending all of the responses to want_config
     * recipient should check if this ID matches our original request nonce, if
     * not, it means your config responses haven't started yet.
     * NOTE: This ID must not change - to keep (minimal) compatibility with <1.2 version of android apps.
     */
    uint32 config_complete_id = 7;
    /*
     * Sent to tell clients the radio has just rebooted.
     * Set to true if present.
     * Not used on all transports, currently just used for the serial console.
     * NOTE: This ID must not change - to keep (minimal) compatibility with <1.2 version of android apps.
     */
    bool rebooted = 8;
    /*
     * Include module config
     */
    ModuleConfig moduleConfig = 9;
    /*
     * One packet is sent for each channel
     */
    Channel channel = 10;
    /*
     * Queue status info
     */
    QueueStatus queueStatus = 11;
    /*
     * File Transfer Chunk
     */
    XModem xmodemPacket = 12;
    /*
     * Device metadata message
     */
    DeviceMetadata metadata = 13;
    /*
     * MQTT Client Proxy Message (device sending to client / phone for publishing to MQTT)
     */
    MqttClientProxyMessage mqttClientProxyMessage = 14;
  }
}

ToRadio

message ToRadio {
  /*
   * Log levels, chosen to match python logging conventions.
   */
  oneof payload_variant {
    /*
     * Send this packet on the mesh
     */
    MeshPacket packet = 1;
    /*
     * Phone wants radio to send full node db to the phone, This is
     * typically the first packet sent to the radio when the phone gets a
     * bluetooth connection. The radio will respond by sending back a
     * MyNodeInfo, a owner, a radio config and a series of
     * FromRadio.node_infos, and config_complete
     * the integer you write into this field will be reported back in the
     * config_complete_id response this allows clients to never be confused by
     * a stale old partially sent config.
     */
    uint32 want_config_id = 3;
    /*
     * Tell API server we are disconnecting now.
     * This is useful for serial links where there is no hardware/protocol based notification that the client has dropped the link.
     * (Sending this message is optional for clients)
     */
    bool disconnect = 4;
    /*
     * File Transfer Chunk
     */
    XModem xmodemPacket = 5;
    /*
     * MQTT Client Proxy Message (for client / phone subscribed to MQTT sending to device)
     */
    MqttClientProxyMessage mqttClientProxyMessage = 6;
    /*
     * Heartbeat message (used to keep the device connection awake on serial)
     */
    Heartbeat heartbeat = 7;
  }
}

Raw Message

Print Code

• 修改了NimbleBluetooth.cpp，將封包透過Hex印出：

class NimbleBluetoothToRadioCallback : public NimBLECharacteristicCallbacks
{
    virtual void onWrite(NimBLECharacteristic *pCharacteristic)
    {
        LOG_INFO("To Radio onwrite\n");
        auto val = pCharacteristic->getValue();

        for(int i = 0; i < val.length(); i++)
            LOG_DEBUG("%2x ", val[i]);
        LOG_DEBUG("\n");

        bluetoothPhoneAPI->handleToRadio(val.data(), val.length());
    }
};

class NimbleBluetoothFromRadioCallback : public NimBLECharacteristicCallbacks
{
    virtual void onRead(NimBLECharacteristic *pCharacteristic)
    {
        LOG_INFO("From Radio onread\n");
        uint8_t fromRadioBytes[meshtastic_FromRadio_size];
        size_t numBytes = bluetoothPhoneAPI->getFromRadio(fromRadioBytes);

        std::string fromRadioByteString(fromRadioBytes, fromRadioBytes + numBytes);

        for(int i = 0; i < fromRadioByteString.length(); i++)
            LOG_DEBUG("%2x ", fromRadioByteString[i]);
        LOG_DEBUG("\n");
        
        pCharacteristic->setValue(fromRadioByteString);
    }
};

• https://github.com/nanopb/nanopb/
  • 用在Radio端進行解碼

ToRadioCharacteristic

• SEND_PACKETS：發送Hello的訊息到Mesh網路

0a 17 15 ff ff ff ff 22 09 08 01 12 05 48 65 6c 6c 6f 35 5b 06 ec 94 50 01

• 0a 17: 表示這是一個 ToRadio 訊息,長度為 0x17(23)個字節。
• 15 ff ff ff ff: 這是一個 Packet 類型的訊息,具有 4 個字節的目的地 ID。
• 22 09: 是協議版本號。
• 08 01: 表示這是一個 DATA_MESSAGE 類型的封包。
• 12 05: 表示接下來有 5 個字節的荷載資料。
• 48 65 6c 6c 6f: 這就是荷載資料,解碼出來是 "Hello" 字串。
• 35 5b 06 ec 94 50 01: 這是一些其他的封包資訊,如來源 ID、crc 校驗碼等。

Reference

• https://meshtastic.org/docs/overview/mesh-algo/
• https://tsunhua.github.io/it/common/protobuf-intro/
• https://protobuf.dev/getting-started/pythontutorial/
• https://protobuf.dev/getting-started/csharptutorial/