Companion Protocol

Last Updated: 2026-08-26
Protocol Version: 14 (FIRMWARE_VER_CODE)

The command and response catalogs track examples/companion_radio/MyMesh.cpp. Applications should negotiate the protocol and validate lengths because older firmware exposes a subset.

This document is a practical guide to MeshCore's binary companion protocol. The same protocol frames can be carried by the enabled BLE, USB serial, Wi-Fi, or Ethernet companion interface; connection details differ by build.

On builds exposing more than one transport, delivery-required replies follow the interface which supplied the command. The multi-frame contact-list response holds that route until END_OF_CONTACTS; best-effort asynchronous observations may still be broadcast to enabled clients. Treat the device as one Companion session rather than as independent per-transport sessions.

The examples focus on BLE, but the packet formats are transport-independent.

Official Libraries

Please see the following repos for existing MeshCore Companion Protocol libraries.

JavaScript: https://github.com/meshcore-dev/meshcore.js
Python: https://github.com/meshcore-dev/meshcore_py

Important Security Note

All secrets, hashes, and cryptographic values shown in this guide are example values only.

All hex values, public keys and hashes are for demonstration purposes only
Never use example secrets in production
Always generate new cryptographically secure random secrets
Please implement proper security practices in your implementation
This guide is for protocol documentation only

BLE Connection

Service and Characteristics

MeshCore Companion devices expose a BLE service with the following UUIDs:

Service UUID: 6E400001-B5A3-F393-E0A9-E50E24DCCA9E
RX Characteristic (App -> Firmware): 6E400002-B5A3-F393-E0A9-E50E24DCCA9E
TX Characteristic (Firmware -> App): 6E400003-B5A3-F393-E0A9-E50E24DCCA9E

An nRF52 Full Companion also exposes a separate LoRa mOTA source service. It does not replace or multiplex the normal Companion UART service:

mOTA Service: 14518FC2-7E7A-4D84-8CAE-6664B0234CF2
Device Request (notify): 2BFAA1EE-7030-459A-B65A-E7CFD5B09735
Host Response (write with response): ACF38A51-DD58-4DCE-917F-0B1135E41B1A

All three mOTA attributes require an encrypted, MITM-authenticated connection using the Companion's six-digit PIN. The source remains inactive until the client subscribes to Device Request and explicitly starts it with command 0x4B. See Bluetooth LoRa mOTA source.

ESP32 and nRF52 Companion UART characteristics require the same PIN-protected, MITM-authenticated link. ESP32 advertises DisplayOnly capability so a central must enter the PIN shown by the Companion; a Just Works bond is insufficient.

Connection Steps

Scan for Devices
- Scan for BLE devices advertising the MeshCore Service UUID
- Optionally filter by device name (typically contains "MeshCore" prefix)
- Note the device MAC address for reconnection
Connect to GATT
- Connect to the device using the discovered MAC address
- Wait for connection to be established
Discover Services and Characteristics
- Discover the service with UUID 6E400001-B5A3-F393-E0A9-E50E24DCCA9E
- Discover the RX characteristic 6E400002-B5A3-F393-E0A9-E50E24DCCA9E
  - Your app writes to this, the firmware reads from this
- Discover the TX characteristic 6E400003-B5A3-F393-E0A9-E50E24DCCA9E
  - The firmware writes to this, your app reads from this
Enable Notifications
- Subscribe to notifications on the TX characteristic to receive data from the firmware
Send Initial Commands
- Send CMD_APP_START to identify your app to firmware and get radio settings
- Send CMD_DEVICE_QUERY to fetch device info and negotiate supported protocol versions
- Send CMD_SET_DEVICE_TIME to set the firmware clock
- Send CMD_GET_CONTACTS to fetch all contacts
- Send CMD_GET_CHANNEL multiple times to fetch all channel slots
- Send CMD_SYNC_NEXT_MESSAGE to fetch the next message stored in firmware
- Setup listeners for push codes, such as PUSH_CODE_MSG_WAITING or PUSH_CODE_ADVERT
- See Commands section for information on other commands

Note: MeshCore devices may disconnect after periods of inactivity. Implement auto-reconnect logic with exponential backoff.

BLE Write Type

When writing commands to the RX characteristic, specify the write type:

Write with Response (default): Waits for acknowledgment from device
Write without Response: Faster but no acknowledgment

Platform-specific:

Android: Use BluetoothGattCharacteristic.WRITE_TYPE_DEFAULT or WRITE_TYPE_NO_RESPONSE
iOS: Use CBCharacteristicWriteType.withResponse or .withoutResponse
Python (bleak): Use write_gatt_char() with response=True or False

Recommendation: Use write with response for reliability.

MTU (Maximum Transmission Unit)

The default BLE MTU is 23 bytes (20 bytes payload). For larger commands like SET_CHANNEL (50 bytes), you may need to:

Request Larger MTU: Request MTU of 512 bytes if supported
- Android: gatt.requestMtu(512)
- iOS: peripheral.maximumWriteValueLength(for:)
- Python (bleak): MTU is negotiated automatically

Command Sequencing

Critical: Commands must be sent in the correct sequence:

After Connection:
- Wait for BLE connection to be established
- Wait for services/characteristics to be discovered
- Wait for notifications to be enabled
- Now you can safely send commands to the firmware
Command-Response Matching:
- Send one command at a time
- Wait for a response before sending another command
- Use a timeout (typically 5 seconds)
- Match response to command by type (e.g: CMD_GET_CHANNEL -> RESP_CODE_CHANNEL_INFO)

Command Queue Management

For reliable operation, implement a command queue.

Queue Structure:

Maintain a queue of pending commands
Track which command is currently waiting for a response
Only send next command after receiving response or timeout

Error Handling:

On timeout, clear current command, process next in queue
On error, log error, clear current command, process next

Packet Structure

The MeshCore protocol uses a binary format with the following structure:

Commands: Sent from app to firmware via RX characteristic
Responses: Received from firmware via TX characteristic notifications
All multi-byte integers: Little-endian byte order (except CayenneLPP which is Big-endian)
All strings: UTF-8 encoding

Most packets follow this format:

[Packet Type (1 byte)] [Data (variable length)]

The first byte indicates the packet type (see Response Parsing).

Commands

The first byte selects the command. This is the current protocol-v14 command catalog; bytes 0x2C-0x31 are parked and 0x35 is unused.

Byte	Firmware name	Purpose
`0x01`	`CMD_APP_START`	Start an app session and request self information.
`0x02`	`CMD_SEND_TXT_MSG`	Send text to a contact.
`0x03`	`CMD_SEND_CHANNEL_TXT_MSG`	Send channel text.
`0x04`	`CMD_GET_CONTACTS`	Enumerate contacts, optionally modified since a timestamp.
`0x05` / `0x06`	`CMD_GET_DEVICE_TIME` / `CMD_SET_DEVICE_TIME`	Read or set the device clock.
`0x07` / `0x08`	`CMD_SEND_SELF_ADVERT` / `CMD_SET_ADVERT_NAME`	Advertise self or change the advertised name.
`0x09`	`CMD_ADD_UPDATE_CONTACT`	Add or update a contact.
`0x0A`	`CMD_SYNC_NEXT_MESSAGE`	Dequeue the next pending message.
`0x0B` / `0x0C`	`CMD_SET_RADIO_PARAMS` / `CMD_SET_RADIO_TX_POWER`	Set radio parameters or transmit power.
`0x0D`	`CMD_RESET_PATH`	Reset a contact's learned path.
`0x0E`	`CMD_SET_ADVERT_LATLON`	Set advertised coordinates.
`0x0F`	`CMD_REMOVE_CONTACT`	Remove a contact.
`0x10` / `0x11` / `0x12`	`CMD_SHARE_CONTACT` / `CMD_EXPORT_CONTACT` / `CMD_IMPORT_CONTACT`	Share, export, or import contact data.
`0x13`	`CMD_REBOOT`	Reboot after the required confirmation body.
`0x14`	`CMD_GET_BATT_AND_STORAGE`	Read battery and storage usage.
`0x15`	`CMD_SET_TUNING_PARAMS`	Set tuning parameters.
`0x16`	`CMD_DEVICE_QUERY`	Negotiate protocol support and read device information.
`0x17` / `0x18`	`CMD_EXPORT_PRIVATE_KEY` / `CMD_IMPORT_PRIVATE_KEY`	Export or import identity key material when enabled.
`0x19`	`CMD_SEND_RAW_DATA`	Send an application raw-data packet.
`0x1A`-`0x1D`	`CMD_SEND_LOGIN` through `CMD_LOGOUT`	Manage a server connection.
`0x1E`	`CMD_GET_CONTACT_BY_KEY`	Look up a contact by public-key prefix.
`0x1F` / `0x20`	`CMD_GET_CHANNEL` / `CMD_SET_CHANNEL`	Read or write a channel slot.
`0x21`-`0x23`	`CMD_SIGN_START` through `CMD_SIGN_FINISH`	Stream data for identity signing.
`0x24`	`CMD_SEND_TRACE_PATH`	Trace a direct route.
`0x25`	`CMD_SET_DEVICE_PIN`	Set or clear the device PIN.
`0x26`	`CMD_SET_OTHER_PARAMS`	Set telemetry, location, ACK, and related preferences.
`0x27`	`CMD_SEND_TELEMETRY_REQ`	Send the legacy telemetry request.
`0x28` / `0x29`	`CMD_GET_CUSTOM_VARS` / `CMD_SET_CUSTOM_VAR`	Read or set custom variables.
`0x2A`	`CMD_GET_ADVERT_PATH`	Read a cached advertisement path.
`0x2B`	`CMD_GET_TUNING_PARAMS`	Read tuning parameters.
`0x32`	`CMD_SEND_BINARY_REQ`	Send an application binary request.
`0x33`	`CMD_FACTORY_RESET`	Factory-reset after the required confirmation body.
`0x34`	`CMD_SEND_PATH_DISCOVERY_REQ`	Request path discovery.
`0x36`	`CMD_SET_FLOOD_SCOPE_KEY`	Select scoped or unscoped flood behavior.
`0x37`	`CMD_SEND_CONTROL_DATA`	Send zero-hop control data.
`0x38`	`CMD_GET_STATS`	Read core, radio, or packet statistics.
`0x39`	`CMD_SEND_ANON_REQ`	Send an anonymous request.
`0x3A` / `0x3B`	`CMD_SET_AUTOADD_CONFIG` / `CMD_GET_AUTOADD_CONFIG`	Write or read automatic-contact policy.
`0x3C`	`CMD_GET_ALLOWED_REPEAT_FREQ`	Read allowed client-repeat frequency ranges.
`0x3D`	`CMD_SET_PATH_HASH_MODE`	Set path-hash width mode.
`0x3E`	`CMD_SEND_CHANNEL_DATA`	Send a channel binary datagram.
`0x3F` / `0x40`	`CMD_SET_DEFAULT_FLOOD_SCOPE` / `CMD_GET_DEFAULT_FLOOD_SCOPE`	Write or read the default flood scope.
`0x41`	`CMD_SEND_RAW_PACKET`	Queue a fully encoded raw mesh packet.
`0x42`	`CMD_RUN_CLI_COMMAND`	Run a local CLI command (protocol v14+).
`0x4A`	`CMD_EXEC_LOCAL_OTA_CONTROL`	Run one bounded local TempRadio or OTA command on a Full Companion.
`0x4B`	`CMD_BLE_MOTA_SOURCE`	Query, start, or stop an nRF52 Full Companion's Bluetooth-backed LoRa mOTA source.
`0x78`-`0x7F`	Deprecated hardware-setting aliases	Receive-only compatibility for clients shipped before command `0x42` became the canonical settings path.

The sections below detail the most common frames. Refer to the source named above for command bodies that are not expanded here.

CMD_RUN_CLI_COMMAND is followed by the local CLI text without a terminating NUL. The device returns RESP_CODE_CLI_REPLY (0x1D) followed by the reply text. This is separate from sending a remote on-air CLI command with CMD_SEND_TXT_MSG and TXT_TYPE_CLI_COMMAND. The body must contain at least one byte and must not contain an embedded NUL. An unknown command is returned as the normal CLI reply text Unknown command, not as an error frame. Clients may prefix the CLI text with any two-character correlation tag and | (for example, A7|get radio.rxgain); the reply preserves that prefix.

Full Companion clients can send version through this command to receive the untruncated build identity, for example Companion 1.17.1.5-... (protocol 14, build 31-Aug-2026). This deliberately supplements rather than changes the 20-byte legacy version field in RESP_CODE_DEVICE_INFO, so existing clients keep the same frame layout.

Firmware from this fork predating the upstream 0x42 allocation used 0x42-0x49 for these eight settings. This firmware accepts those values as deprecated inbound aliases so existing clients continue to work. A one-byte 0x42 frame is the legacy FEM-gain GET; 0x42 followed by text is the official CMD_RUN_CLI_COMMAND. New clients should use CMD_RUN_CLI_COMMAND for all of these settings, rather than allocating additional command bytes. For example, send 0x42 followed by get radio.rxgain or set radio.rxgain on. The reply is RESP_CODE_CLI_REPLY followed by the normal CLI reply text.

Two deprecated binary alias blocks remain receive-only for compatibility:

Setting	Original alias	Later fork alias	GET body/reply	SET body/reply
FEM receive gain	`0x42` / `0x43`	`0x78` / `0x79`	No body; `OK, state`	One byte `0`/`1`; `OK`
Radio receive gain	`0x44` / `0x45`	`0x7A` / `0x7B`	No body; `OK, state`	One byte `0`/`1`; `OK`
WiFi power save	`0x46` / `0x47`	`0x7C` / `0x7D`	No body; `OK, mode`	One mode byte `0`-`2`; `OK`
Bluetooth name	`0x48` / `0x49`	`0x7E` / `0x7F`	No body; `OK, custom, name`	Zero to 31 UTF-8 bytes; `OK`

Each pair lists GET then SET. Here OK is RESP_CODE_OK; the remaining reply bytes have the same meanings as the CLI settings below. A bare 0x42 is the old FEM GET, while 0x42 plus at least one text byte is CMD_RUN_CLI_COMMAND. New clients must use the framed CLI form; these aliases exist only so deployed clients do not break after a firmware update.

The equivalent framed CLI commands are:

Setting	Commands
Radio receive gain	`get radio.rxgain`; `set radio.rxgain on\|off`
FEM receive gain	`get radio.fem.rxgain`; `set radio.fem.rxgain on\|off`
WiFi power save	`get wifi.powersave`; `set wifi.powersave none\|min\|max`
Bluetooth name	`get bluetooth.name`; `set bluetooth.name <name\|default>`

The framed form works over the normal binary USB, BLE, or TCP transport and does not need the USB terminal-start token. Unsupported settings return the same explanatory text as the local CLI.

WiFi power-save modes are:

Value	Mode
`0`	`min` - minimum modem sleep
`1`	`none` - no modem sleep
`2`	`max` - maximum modem sleep

A Full Companion that runs BLE and infrastructure WiFi simultaneously rejects WiFi mode none because coexistence requires modem sleep. A Full Companion using ESP-NOW as its primary mesh radio also rejects max, because maximum modem sleep can miss broadcasts that the access point cannot buffer. If an older image saved a conflicting value, the effective mode is capped to and reported as min. Device powersaving remains independent.

The SenseCAP Indicator Full profiles run exactly one secondary wireless Companion transport per boot. Their active-mode constraints are:

Indicator mode	Accepted `wifi.powersave` values
LoRa + infrastructure WiFi	`none`, `min`, `max`
LoRa + BLE	`min`, `max`; infrastructure WiFi is not started
ESP-NOW + infrastructure WiFi	`none`, `min`; `max` conflicts with primary ESP-NOW
ESP-NOW + BLE	`min`; infrastructure WiFi is not started and primary ESP-NOW remains active

The Bluetooth name can be configured over USB, BLE, or TCP. Use set bluetooth.name default to restore MeshCore-<advert name>; an empty CLI value is rejected. (clear is also accepted as an alias for default.) A custom name is limited to 31 valid UTF-8 bytes and takes effect after reboot.

Bluetooth LoRa mOTA source

Protocol v14 lets a phone use an nRF52 Full Companion as the source for a remote repeater update without a USB computer. The normal Companion service still carries contacts, repeater login, CLI messages, and these two control commands. The separate mOTA service carries only host-folder request/response frames.

CMD_EXEC_LOCAL_OTA_CONTROL (0x4A) is followed by 1-174 printable ASCII bytes. Full Companion accepts only these local command families:

tempradio <freq_kHz>,<bw_kHz>,<sf>,<cr>,<minutes>
normalradio
ota ...

ota folder ... is deliberately rejected because USB and Bluetooth source ownership must not be changed through the wrong transport. Embedded NUL, CR, LF, other control bytes, non-ASCII bytes, empty commands, and oversized frames return ERR_CODE_ILLEGAL_ARG. A recognized command replies with RESP_CODE_OK, one unsigned reply-length byte, and exactly that many printable result bytes. Shell metacharacters are rejected as well; the text is dispatched only to the in-firmware parser and is never passed to a host shell. Firmware without the Full Companion feature returns ERR_CODE_UNSUPPORTED_CMD.

CMD_BLE_MOTA_SOURCE (0x4B) has one action byte:

Action	Meaning
`0`	Read status without changing it.
`1`	Attach and enumerate the subscribed Bluetooth host's `.mota` catalog.
`2`	Detach the Bluetooth source.

Current firmware returns eleven bytes (legacy protocol-v14 previews returned the seven-byte prefix only):

00 action flags offered_le16 advertised_le16 source_packets_sent_le32

Flag bit 0x01 means the encrypted GATT channel is connected and Device Request notifications are enabled. Bit 0x02 means the Bluetooth catalog is attached. Bit 0x04 means USB or another folder transport currently owns the source slot. Start without a ready subscription, or while another source link owns the slot, returns ERR_CODE_BAD_STATE. A non-nRF52 Full Companion returns ERR_CODE_UNSUPPORTED_CMD. source_packets_sent is a per-attachment count of OTA packets accepted by the Companion's LoRa transmit adapter, including catalog/manifest traffic, data, proofs, and retries. It wraps as an unsigned 32-bit value. Clients should accept the legacy seven-byte response and display the packet counter as unavailable.

After a successful start, the device sends the same bounded seeder frames used by motatool serve on Device Request:

device -> host: 'M' 'S' op args... xor(op || args)
host -> device: 'm' 's' op status payload... xor(all prior bytes)

Device requests are at most 11 bytes. A source response is at most 197 bytes. The host may split one response across multiple write-with-response operations when the negotiated ATT payload is smaller; it must preserve byte order and must not interleave another response. Bad checksums, partial frames, overflow, unsubscribe, loss of encryption, or disconnect fail closed. The firmware then detaches the catalog and stops advertising its entries. USB and Bluetooth folder sources are mutually exclusive.

A Linux reference controller and seeder is provided at tools/ble_mota/ble_mota_seeder.py. It verifies every input with motatool before offering it. A mobile implementation should apply the same complete container verification before serving files.

1. App Start

Purpose: Initialize communication with the device. Must be sent first after connection.

Command Format:

Byte 0: 0x01
Bytes 1-7: Reserved (currently ignored by firmware)
Bytes 8+: Application name (UTF-8, optional)

Example (hex):

01 00 00 00 00 00 00 00 6d 63 63 6c 69

Response: PACKET_SELF_INFO (0x05)

2. Device Query

Purpose: Query device information.

Command Format:

Byte 0: 0x16
Byte 1: Highest companion protocol version understood by the app

Example (hex):

16 0E

Response: PACKET_DEVICE_INFO (0x0D) with device information

3. Get Channel Info

Purpose: Retrieve information about a specific channel.

Command Format:

Byte 0: 0x1F
Byte 1: Channel index (0 through max_channels - 1)

Example (get channel 1):

1F 01

Response: PACKET_CHANNEL_INFO (0x12) with channel details

4. Set Channel

Purpose: Create or update a channel on the device.

Command Format:

Byte 0: 0x20
Byte 1: Channel index (0 through max_channels - 1)
Bytes 2-33: Channel Name (32 bytes, UTF-8, null-padded)
Bytes 34-49: Secret (16 bytes)

Total Length: 50 bytes

Channel index: - Slot count is build-specific. Read max_channels from byte 3 of PACKET_DEVICE_INFO; current profiles commonly expose 1, 8, or 40 slots. - No slot number has an intrinsic public/private meaning.

Channel Name: - UTF-8 encoded - Maximum 32 bytes - Padded with null bytes (0x00) if shorter

Secret Field (16 bytes): - Supply the exact 16-byte channel key. A private channel normally uses a cryptographically random key; known public and hashtag channels use their defined or derived key. - An all-zero key is not the public-channel key.

Example (create channel "SMS" at index 1 with secret):

20 01 53 4D 53 00 00 ... (name padded to 32 bytes)
    [16 bytes of secret]

Note: The 32-byte secret variant is unsupported and returns PACKET_ERROR.

Response: PACKET_OK (0x00) on success, PACKET_ERROR (0x01) on failure

5. Send Channel Message

Purpose: Send a text message to a channel.

Command Format:

Byte 0: 0x03
Byte 1: 0x00
Byte 2: Channel index (0 through max_channels - 1)
Bytes 3-6: Timestamp (32-bit little-endian Unix timestamp, seconds)
Bytes 7+: Message Text (UTF-8, variable length)

Timestamp: Unix timestamp in seconds (32-bit unsigned integer, little-endian)

Example (send "Hello" to channel 1 at timestamp 1234567890):

03 00 01 D2 02 96 49 48 65 6C 6C 6F

Response: PACKET_MSG_SENT (0x06) on success

6. Send Channel Data Datagram

Purpose: Send a binary datagram to a channel. Unlike channel text messages, datagrams carry no built-in sender identity and no timestamp - applications needing either must encode them inside the binary payload.

Command Format:

Byte 0:                         0x3E
Byte 1:                         Channel index (0 through max_channels - 1)
Byte 2:                         Encoded path descriptor (0xFF = flood)
Bytes 3+:                       Encoded path bytes (omitted for 0xFF)
Next 2 bytes (little-endian):   Data Type (`data_type`, uint16)
Remaining bytes:                Binary payload (variable length)

For a direct send, the descriptor's low six bits are the hash count and its high two bits are the hash size minus one. Current mesh packets accept one-, two-, or three-byte hashes; the four-byte code is reserved. The following path therefore occupies hash_count * hash_size bytes; the descriptor itself is not a raw byte count.

Example (flood, DATA_TYPE_DEV, payload A1 B2 C3, channel 1):

3E 01 FF FF FF A1 B2 C3

Data Type / Transport Mapping: - 0x0000 (DATA_TYPE_RESERVED) is invalid and rejected with PACKET_ERROR. - 0xFFFF (DATA_TYPE_DEV) is the developer namespace for experimenting and developing apps. - Registered application/community namespaces occupy 0x0100-0xFEFF; the remaining nonzero ranges are reserved for internal or development use. See the Registered data_type values table below.

Limits: - Maximum payload length is MAX_CHANNEL_DATA_LENGTH = MAX_FRAME_SIZE - 9 = 167 bytes. - Larger payloads are rejected with PACKET_ERROR (ERR_CODE_ILLEGAL_ARG).

Response: PACKET_OK (0x00) on success, or PACKET_ERROR (0x01) with one of: - ERR_CODE_NOT_FOUND (2) - unknown channel_idx - ERR_CODE_ILLEGAL_ARG (6) - invalid path_len, reserved data_type (0x0000), or payload larger than MAX_CHANNEL_DATA_LENGTH - ERR_CODE_TABLE_FULL (3) - outbound send queue is full; retry later

Inbound datagrams are delivered to the host via RESP_CODE_CHANNEL_DATA_RECV (0x1B); see Receive Channel Data Datagram.

Registered `data_type` values

data_type is an application identifier, not a payload-format identifier. Each registered value identifies an application that owns its own internal payload schemas. The firmware does not inspect payload contents - data_type is transported opaquely.

Value	Constant	Purpose
0x0000	`DATA_TYPE_RESERVED`	Reserved; invalid on send
0x0001 - 0x00FF	-	Reserved for internal use
0x0100 - 0xFEFF	-	Registered application namespaces (see number_allocations.md)
0xFF00 - 0xFFFE	-	Testing/development; no registration required
0xFFFF	`DATA_TYPE_DEV`	Developer/experimental namespace

To register a new application, submit a PR adding a row to the table in docs/number_allocations.md. Internal sub-formats within an allocated application ID are owned by that application and are not tracked in MeshCore firmware or this document.

Receive Channel Data Datagram

Inbound group datagrams (radio-level PAYLOAD_TYPE_GRP_DATA, 0x06) are forwarded to the host as RESP_CODE_CHANNEL_DATA_RECV notifications.

Frame Format (RESP_CODE_CHANNEL_DATA_RECV, 0x1B):

Byte 0:                 0x1B (packet type)
Byte 1:                 SNR (signed int8, scaled x4 - divide by 4.0 to recover dB)
Bytes 2-3:              Reserved (clients MUST ignore)
Byte 4:                 Channel index (0 through max_channels - 1)
Byte 5:                 Path Length (actual path length when flooded, otherwise 0xFF for direct)
Bytes 6-7:              Data Type (uint16 little-endian)
Byte 8:                 Data Length
Bytes 9 .. 8+data_len:  Payload

Path bytes are not forwarded: Only path_len is reported in the receive frame - the path itself is not copied to the host. There are no path bytes between byte 5 and the data_type field at bytes 6-7, regardless of path_len.

Path Length semantics differ between send and receive:

Direction	`path_len = 0xFF`	`path_len != 0xFF`
Send	Flood the network	Direct route; the encoded path follows (low 6 bits = hash count, top 2 bits + 1 = hash size; on-wire byte count = `hash_count x hash_size`)
Receive	Packet arrived via direct route	Packet was flooded; this is the encoded `pkt->path_len` field as observed (no path bytes follow)

In other words, the meaning of 0xFF is inverted between the two directions, and on receive the field carries metadata only - never a routable path. path_len is an encoded byte (see Packet::isValidPathLen / Packet::writePath in src/Packet.cpp), not a raw byte count.

Note: The device may also emit PACKET_MESSAGES_WAITING (0x83) to notify the host that datagrams are queued; poll with CMD_SYNC_NEXT_MESSAGE (0x0A) to retrieve them.

Parsing Pseudocode:

def parse_channel_data_recv(data):
    if len(data) < 9:
        return None
    snr_byte = data[1]
    snr = (snr_byte if snr_byte < 128 else snr_byte - 256) / 4.0
    channel_idx = data[4]
    path_len = data[5]
    data_type = int.from_bytes(data[6:8], 'little')
    data_len = data[8]
    if 9 + data_len > len(data):
        return None
    payload = data[9:9 + data_len]
    return {
        'snr': snr,
        'channel_idx': channel_idx,
        'path_len': path_len,
        'data_type': data_type,
        'payload': bytes(payload),
    }

7. Get Message

Purpose: Request the next queued message from the device.

Command Format:

Byte 0: 0x0A

Example (hex):

0A

Response: - PACKET_CHANNEL_MSG_RECV (0x08) or PACKET_CHANNEL_MSG_RECV_V3 (0x11) for channel messages - PACKET_CONTACT_MSG_RECV (0x07) or PACKET_CONTACT_MSG_RECV_V3 (0x10) for contact messages - PACKET_CHANNEL_DATA_RECV (0x1B) for channel data datagrams - PACKET_NO_MORE_MSGS (0x0A) if no messages available

Note: Poll this command periodically to retrieve queued messages. The device may also send PACKET_MESSAGES_WAITING (0x83) as a notification when messages are available.

8. Get Battery and Storage

Purpose: Query device battery voltage and storage usage.

Command Format:

Byte 0: 0x14

Example (hex):

Response: PACKET_BATTERY (0x0C) with battery millivolts and storage information

Channel Management

Channel Types

Public Channel
- Uses a publicly known 16-byte key: 8b3387e9c5cdea6ac9e5edbaa115cd72
- Anyone can join this channel, messages should be considered public
- Used as the default public group chat
Hashtag Channels
- Uses a secret key derived from the channel name
- It is the first 16 bytes of sha256("#test")
- For example hashtag channel #test has the key: 9cd8fcf22a47333b591d96a2b848b73f
- Traffic is encrypted on air, but anyone who knows or guesses the channel name can derive the key. Hashtag channels should not be treated as private.
- Used as a topic based public group chat, separate from the default public channel
Private Channels
- Uses a randomly generated 16-byte secret key
- Messages should be considered private between those that know the secret
- Users should keep the key secret, and only share with those you want to communicate with
- Used as a secure private group chat

Channel Lifecycle

Set Channel:
- Read max_channels from device info, fetch those slots, and choose an unused slot (normally an empty name and zeroed key)
- Generate or provide a 16-byte secret
- Send CMD_SET_CHANNEL with name and a 16-byte secret
Get Channel:
- Send CMD_GET_CHANNEL with channel index
- Parse RESP_CODE_CHANNEL_INFO response
Delete Channel:
- Send CMD_SET_CHANNEL with empty name and all-zero secret
- Or overwrite with a new channel

Message Handling

Receiving Messages

Messages are received via the TX characteristic (notifications). The device sends:

Channel Messages:
PACKET_CHANNEL_MSG_RECV (0x08) - Standard format
PACKET_CHANNEL_MSG_RECV_V3 (0x11) - Version 3 with SNR
Contact Messages:
PACKET_CONTACT_MSG_RECV (0x07) - Standard format
PACKET_CONTACT_MSG_RECV_V3 (0x10) - Version 3 with SNR
Notifications:
PACKET_MESSAGES_WAITING (0x83) - Indicates messages are queued

Contact Message Format

Standard Format (PACKET_CONTACT_MSG_RECV, 0x07):

Byte 0: 0x07 (packet type)
Bytes 1-6: Public Key Prefix (6 bytes, hex)
Byte 7: Path Length
Byte 8: Text Type
Bytes 9-12: Timestamp (32-bit little-endian)
Bytes 13-16: Signature (4 bytes, only if txt_type == 2)
Bytes 17+: Message Text (UTF-8)

V3 Format (PACKET_CONTACT_MSG_RECV_V3, 0x10):

Byte 0: 0x10 (packet type)
Byte 1: SNR (signed byte, multiplied by 4)
Bytes 2-3: Reserved
Bytes 4-9: Public Key Prefix (6 bytes, hex)
Byte 10: Path Length
Byte 11: Text Type
Bytes 12-15: Timestamp (32-bit little-endian)
Bytes 16-19: Signature (4 bytes, only if txt_type == 2)
Bytes 20+: Message Text (UTF-8)

Parsing Pseudocode:

def parse_contact_message(data):
    packet_type = data[0]
    offset = 1

    # Check for V3 format
    if packet_type == 0x10:  # V3
        snr_byte = data[offset]
        snr = ((snr_byte if snr_byte < 128 else snr_byte - 256) / 4.0)
        offset += 3  # Skip SNR + reserved

    pubkey_prefix = data[offset:offset+6].hex()
    offset += 6

    path_len = data[offset]
    txt_type = data[offset + 1]
    offset += 2

    timestamp = int.from_bytes(data[offset:offset+4], 'little')
    offset += 4

    # If txt_type == 2, skip 4-byte signature
    if txt_type == 2:
        offset += 4

    message = data[offset:].decode('utf-8')

    return {
        'pubkey_prefix': pubkey_prefix,
        'path_len': path_len,
        'txt_type': txt_type,
        'timestamp': timestamp,
        'message': message,
        'snr': snr if packet_type == 0x10 else None
    }

Channel Message Format

Standard Format (PACKET_CHANNEL_MSG_RECV, 0x08):

Byte 0: 0x08 (packet type)
Byte 1: Channel index (0 through max_channels - 1)
Byte 2: Path Length
Byte 3: Text Type
Bytes 4-7: Timestamp (32-bit little-endian)
Bytes 8+: Message Text (UTF-8)

V3 Format (PACKET_CHANNEL_MSG_RECV_V3, 0x11):

Byte 0: 0x11 (packet type)
Byte 1: SNR (signed byte, multiplied by 4)
Bytes 2-3: Reserved
Byte 4: Channel index (0 through max_channels - 1)
Byte 5: Path Length
Byte 6: Text Type
Bytes 7-10: Timestamp (32-bit little-endian)
Bytes 11+: Message Text (UTF-8)

Parsing Pseudocode:

def parse_channel_message(data):
    packet_type = data[0]
    offset = 1

    # Check for V3 format
    if packet_type == 0x11:  # V3
        snr_byte = data[offset]
        snr = ((snr_byte if snr_byte < 128 else snr_byte - 256) / 4.0)
        offset += 3  # Skip SNR + reserved

    channel_idx = data[offset]
    path_len = data[offset + 1]
    txt_type = data[offset + 2]
    timestamp = int.from_bytes(data[offset+3:offset+7], 'little')
    message = data[offset+7:].decode('utf-8')

    return {
        'channel_idx': channel_idx,
        'timestamp': timestamp,
        'message': message,
        'snr': snr if packet_type == 0x11 else None
    }

Sending Messages

Use the SEND_CHANNEL_MESSAGE command (see Commands).

Important: - The shared text envelope permits up to 160 UTF-8 bytes. For channel text, firmware prepends <sender name>: inside that envelope, so the available message body is 160 - prefix_bytes and varies with the configured name. - Count encoded UTF-8 bytes, not Unicode characters. Split a longer message at valid UTF-8 boundaries. - Include a chunk indicator (e.g., "[1/3] message text")

Response Parsing

Terminology

This document uses a spec-level naming convention (PACKET_*) for bytes the firmware sends back to the host. In the firmware source these same values are split across two #define families by purpose:

RESP_CODE_* - direct replies to a command (e.g. RESP_CODE_CHANNEL_DATA_RECV = PACKET_CHANNEL_DATA_RECV = 0x1B).
PUSH_CODE_* - asynchronous notifications not tied to a specific command (e.g. PUSH_CODE_MSG_WAITING = PACKET_MESSAGES_WAITING = 0x83).

Byte values are authoritative; names are aliases. When reading firmware source, RESP_CODE_X / PUSH_CODE_X correspond to this doc's PACKET_X of the same numeric value.

Response types

Value	Firmware name	Description
`0x00`	`RESP_CODE_OK`	Command succeeded.
`0x01`	`RESP_CODE_ERR`	Command failed; byte 1 is the error code.
`0x02`	`RESP_CODE_CONTACTS_START`	Contact enumeration started.
`0x03`	`RESP_CODE_CONTACT`	One contact record.
`0x04`	`RESP_CODE_END_OF_CONTACTS`	Contact enumeration ended.
`0x05`	`RESP_CODE_SELF_INFO`	Device self-information.
`0x06`	`RESP_CODE_SENT`	Send accepted, with route/tag/timeout data.
`0x07` / `0x08`	`RESP_CODE_CONTACT_MSG_RECV` / `RESP_CODE_CHANNEL_MSG_RECV`	Queued legacy-format message.
`0x09`	`RESP_CODE_CURR_TIME`	Current device time.
`0x0A`	`RESP_CODE_NO_MORE_MESSAGES`	Offline queue is empty.
`0x0B`	`RESP_CODE_EXPORT_CONTACT`	Exported contact bytes.
`0x0C`	`RESP_CODE_BATT_AND_STORAGE`	Battery and storage values.
`0x0D`	`RESP_CODE_DEVICE_INFO`	Protocol and build information.
`0x0E`	`RESP_CODE_PRIVATE_KEY`	Exported identity key, when enabled.
`0x0F`	`RESP_CODE_DISABLED`	Requested sensitive feature is disabled.
`0x10` / `0x11`	`RESP_CODE_CONTACT_MSG_RECV_V3` / `RESP_CODE_CHANNEL_MSG_RECV_V3`	Queued message with SNR fields.
`0x12`	`RESP_CODE_CHANNEL_INFO`	Channel slot information.
`0x13` / `0x14`	`RESP_CODE_SIGN_START` / `RESP_CODE_SIGNATURE`	Signing capacity or completed signature.
`0x15`	`RESP_CODE_CUSTOM_VARS`	Custom-variable data.
`0x16`	`RESP_CODE_ADVERT_PATH`	Cached advertisement path.
`0x17`	`RESP_CODE_TUNING_PARAMS`	Tuning parameters.
`0x18`	`RESP_CODE_STATS`	Requested statistics subtype.
`0x19`	`RESP_CODE_AUTOADD_CONFIG`	Automatic-contact policy.
`0x1A`	`RESP_ALLOWED_REPEAT_FREQ`	Allowed repeat-frequency ranges.
`0x1B`	`RESP_CODE_CHANNEL_DATA_RECV`	Queued channel datagram.
`0x1C`	`RESP_CODE_DEFAULT_FLOOD_SCOPE`	Default flood-scope data.
`0x1D`	`RESP_CODE_CLI_REPLY`	Text returned by `CMD_RUN_CLI_COMMAND`.

Asynchronous push types

Value	Firmware name	Description
`0x80`	`PUSH_CODE_ADVERT`	Advertisement received.
`0x81`	`PUSH_CODE_PATH_UPDATED`	A contact path changed.
`0x82`	`PUSH_CODE_SEND_CONFIRMED`	A sent message was acknowledged.
`0x83`	`PUSH_CODE_MSG_WAITING`	One or more offline frames are waiting.
`0x84`	`PUSH_CODE_RAW_DATA`	Raw application data received.
`0x85` / `0x86`	`PUSH_CODE_LOGIN_SUCCESS` / `PUSH_CODE_LOGIN_FAIL`	Server login result.
`0x87`	`PUSH_CODE_STATUS_RESPONSE`	Server status response.
`0x88`	`PUSH_CODE_LOG_RX_DATA`	Radio receive log data.
`0x89`	`PUSH_CODE_TRACE_DATA`	Completed trace data.
`0x8A`	`PUSH_CODE_NEW_ADVERT`	Newly stored contact advertisement.
`0x8B`	`PUSH_CODE_TELEMETRY_RESPONSE`	Telemetry response.
`0x8C`	`PUSH_CODE_BINARY_RESPONSE`	Binary request response.
`0x8D`	`PUSH_CODE_PATH_DISCOVERY_RESPONSE`	Path-discovery response.
`0x8E`	`PUSH_CODE_CONTROL_DATA`	Control/discovery data.
`0x8F`	`PUSH_CODE_CONTACT_DELETED`	Oldest contact was deleted while making room.
`0x90`	`PUSH_CODE_CONTACTS_FULL`	Contact storage is full.

Parsing Responses

PACKET_OK (0x00):

Byte 0: 0x00
Bytes 1-4: Optional value (32-bit little-endian integer)

PACKET_ERROR (0x01):

Byte 0: 0x01
Byte 1: Error code (optional)

PACKET_CHANNEL_INFO (0x12):

Byte 0: 0x12
Byte 1: Channel Index
Bytes 2-33: Channel Name (32 bytes, null-terminated)
Bytes 34-49: Secret (16 bytes)

Note: The device returns the 16-byte channel secret in this response.

PACKET_DEVICE_INFO (0x0D):

Byte 0: 0x0D
Byte 1: Firmware Version (uint8)
Bytes 2+: Variable length based on firmware version

For firmware version >= 3:
Byte 2: Max Contacts Raw (uint8, actual = value * 2)
Byte 3: Max Channels (uint8)
Bytes 4-7: Active BLE PIN (32-bit little-endian; includes a generated session PIN)
Bytes 8-19: Firmware Build (12 bytes, UTF-8, null-padded)
Bytes 20-59: Model (40 bytes, UTF-8, null-padded)
Bytes 60-79: Version (20 bytes, UTF-8, null-padded)
Byte 80: Client repeat enabled/preferred (firmware v9+)
Byte 81: Path hash mode (firmware v10+)

Parsing Pseudocode:

def parse_device_info(data):
    if len(data) < 2:
        return None

    fw_ver = data[1]
    info = {'fw_ver': fw_ver}

    if fw_ver >= 3 and len(data) >= 80:
        info['max_contacts'] = data[2] * 2
        info['max_channels'] = data[3]
        info['ble_pin'] = int.from_bytes(data[4:8], 'little')
        info['fw_build'] = data[8:20].decode('utf-8').rstrip('\x00').strip()
        info['model'] = data[20:60].decode('utf-8').rstrip('\x00').strip()
        info['ver'] = data[60:80].decode('utf-8').rstrip('\x00').strip()

    if fw_ver >= 9 and len(data) >= 81:
        info['client_repeat'] = data[80] != 0
    if fw_ver >= 10 and len(data) >= 82:
        info['path_hash_mode'] = data[81]

    return info

PACKET_BATTERY (0x0C):

Byte 0: 0x0C
Bytes 1-2: Battery Voltage (16-bit little-endian, millivolts)
Bytes 3-6: Used Storage (32-bit little-endian, KB)
Bytes 7-10: Total Storage (32-bit little-endian, KB)

Parsing Pseudocode:

def parse_battery(data):
    if len(data) < 3:
        return None

    mv = int.from_bytes(data[1:3], 'little')
    info = {'battery_mv': mv}

    if len(data) >= 11:
        info['used_kb'] = int.from_bytes(data[3:7], 'little')
        info['total_kb'] = int.from_bytes(data[7:11], 'little')

    return info

PACKET_SELF_INFO (0x05):

Byte 0: 0x05
Byte 1: Advertisement Type
Byte 2: TX Power
Byte 3: Max TX Power
Bytes 4-35: Public Key (32 bytes, hex)
Bytes 36-39: Advertisement Latitude (32-bit little-endian, divided by 1e6)
Bytes 40-43: Advertisement Longitude (32-bit little-endian, divided by 1e6)
Byte 44: Multi ACKs
Byte 45: Advertisement Location Policy
Byte 46: Telemetry Mode (bitfield)
Byte 47: Manual Add Contacts (bool)
Bytes 48-51: Radio Frequency (32-bit little-endian, divided by 1000.0)
Bytes 52-55: Radio Bandwidth (32-bit little-endian, divided by 1000.0)
Byte 56: Radio Spreading Factor
Byte 57: Radio Coding Rate
Bytes 58+: Device Name (UTF-8, variable length, no null terminator required)

Parsing Pseudocode:

def parse_self_info(data):
    if len(data) < 36:
        return None

    offset = 1
    info = {
        'adv_type': data[offset],
        'tx_power': data[offset + 1],
        'max_tx_power': data[offset + 2],
        'public_key': data[offset + 3:offset + 35].hex()
    }
    offset += 35

    lat = int.from_bytes(data[offset:offset+4], 'little') / 1e6
    lon = int.from_bytes(data[offset+4:offset+8], 'little') / 1e6
    info['adv_lat'] = lat
    info['adv_lon'] = lon
    offset += 8

    info['multi_acks'] = data[offset]
    info['adv_loc_policy'] = data[offset + 1]
    telemetry_mode = data[offset + 2]
    info['telemetry_mode_env'] = (telemetry_mode >> 4) & 0b11
    info['telemetry_mode_loc'] = (telemetry_mode >> 2) & 0b11
    info['telemetry_mode_base'] = telemetry_mode & 0b11
    info['manual_add_contacts'] = data[offset + 3] > 0
    offset += 4

    freq = int.from_bytes(data[offset:offset+4], 'little') / 1000.0
    bw = int.from_bytes(data[offset+4:offset+8], 'little') / 1000.0
    info['radio_freq'] = freq
    info['radio_bw'] = bw
    info['radio_sf'] = data[offset + 8]
    info['radio_cr'] = data[offset + 9]
    offset += 10

    if offset < len(data):
        name_bytes = data[offset:]
        info['name'] = name_bytes.decode('utf-8').rstrip('\x00').strip()

    return info

PACKET_MSG_SENT (0x06):

Byte 0: 0x06
Byte 1: Route Flag (0 = direct, 1 = flood)
Bytes 2-5: Tag / Expected ACK (4 bytes, little-endian)
Bytes 6-9: Suggested Timeout (32-bit little-endian, milliseconds)

PACKET_SEND_CONFIRMED (0x82):

Byte 0: 0x82
Bytes 1-4: ACK code (32-bit little-endian)
Bytes 5-8: Round-trip time (32-bit little-endian, milliseconds)

Error Codes

PACKET_ERROR (0x01) carries a single-byte error code in byte 1. Values match the ERR_CODE_* constants defined in examples/companion_radio/MyMesh.cpp:

Code	Constant (firmware)	Description
1	`ERR_CODE_UNSUPPORTED_CMD`	Unknown or unsupported command byte / sub-command
2	`ERR_CODE_NOT_FOUND`	Target not found (channel, contact, message, etc.)
3	`ERR_CODE_TABLE_FULL`	Internal queue or table is full - retry later
4	`ERR_CODE_BAD_STATE`	Operation not valid in current device state (e.g. iterator already running)
5	`ERR_CODE_FILE_IO_ERROR`	Filesystem or storage I/O failure
6	`ERR_CODE_ILLEGAL_ARG`	Invalid argument (bad length, out-of-range value, reserved field, etc.)

Note: Error codes may vary by firmware version. Always check byte 1 of PACKET_ERROR response, and treat unknown codes as generic errors.

Frame Handling

BLE implementations enqueue and deliver one protocol frame per BLE write/notification at the firmware layer.

Apps should treat each characteristic write/notification as exactly one companion protocol frame
Apps should still validate frame lengths before parsing
Future transports or firmware revisions may differ, so avoid assuming fixed payload sizes for variable-length responses

Response Handling

Command-Response Pattern:
Send command via RX characteristic
Wait for response via TX characteristic (notification)
Match the response by the expected response type; frames do not carry a general command sequence number
Handle timeout (typically 5 seconds)
Use command queue to prevent concurrent commands
Asynchronous Messages:
Device may send messages at any time via TX characteristic
Handle PACKET_MESSAGES_WAITING (0x83) by polling GET_MESSAGE command
Parse incoming messages and route to appropriate handlers
Validate frame length before decoding
Response Matching:
Match responses to commands by expected packet type:
- APP_START -> PACKET_SELF_INFO
- DEVICE_QUERY -> PACKET_DEVICE_INFO
- GET_CHANNEL -> PACKET_CHANNEL_INFO
- SET_CHANNEL -> PACKET_OK or PACKET_ERROR
- SEND_CHANNEL_MESSAGE -> PACKET_MSG_SENT
- GET_MESSAGE -> PACKET_CHANNEL_MSG_RECV, PACKET_CONTACT_MSG_RECV, PACKET_CHANNEL_DATA_RECV, or PACKET_NO_MORE_MSGS
- SEND_CHANNEL_DATA -> PACKET_OK or PACKET_ERROR
- GET_BATTERY -> PACKET_BATTERY
Timeout Handling:
Default timeout: 5 seconds per command
On timeout: Log error, clear current command, proceed to next in queue
Some commands may take longer (e.g., SET_CHANNEL may need 1-2 seconds)
Consider longer timeout for channel operations
Error Recovery:
On PACKET_ERROR: Log error code, clear current command
On connection loss: Clear command queue, attempt reconnection
On invalid response: Log warning, clear current command, proceed

Example Implementation Flow

Initialization

# 1. Scan for MeshCore device
device = scan_for_device("MeshCore")

# 2. Connect to BLE GATT
gatt = connect_to_device(device)

# 3. Discover services and characteristics
service = discover_service(gatt, "6E400001-B5A3-F393-E0A9-E50E24DCCA9E")
rx_char = discover_characteristic(service, "6E400002-B5A3-F393-E0A9-E50E24DCCA9E")
tx_char = discover_characteristic(service, "6E400003-B5A3-F393-E0A9-E50E24DCCA9E")

# 4. Enable notifications on TX characteristic
enable_notifications(tx_char, on_notification_received)

# 5. Send AppStart command
send_command(rx_char, build_app_start())
wait_for_response(PACKET_SELF_INFO)

Creating a Private Channel

# 1. Generate 16-byte secret
secret_16_bytes = generate_secret(16)  # Use CSPRNG
secret_hex = secret_16_bytes.hex()

# 2. Build SET_CHANNEL command
channel_name = "YourChannelName"
channel_index = choose_unused_slot(max_channels)
command = build_set_channel(channel_index, channel_name, secret_16_bytes)

# 3. Send command
send_command(rx_char, command)
response = wait_for_response(PACKET_OK)

# 4. Store secret locally
store_channel_secret(channel_index, secret_hex)

Sending a Message

# 1. Build channel message command
channel_index = 1
message = "Hello, MeshCore!"
timestamp = int(time.time())
command = build_channel_message(channel_index, message, timestamp)

# 2. Send command
send_command(rx_char, command)
response = wait_for_response(PACKET_MSG_SENT)

Receiving Messages

def on_notification_received(data):
    packet_type = data[0]

    if packet_type == PACKET_CHANNEL_MSG_RECV or packet_type == PACKET_CHANNEL_MSG_RECV_V3:
        message = parse_channel_message(data)
        handle_channel_message(message)
    elif packet_type == PACKET_MESSAGES_WAITING:
        # Poll for messages
        send_command(rx_char, build_get_message())

Best Practices

Connection Management:
Implement auto-reconnect with exponential backoff
Handle disconnections gracefully
Store last connected device address for quick reconnection
Secret Management:
Always use cryptographically secure random number generators
Store secrets securely (encrypted storage)
Never log or transmit secrets in plain text
Message Handling:
Send CMD_SYNC_NEXT_MESSAGE when PUSH_CODE_MSG_WAITING is received
Implement message deduplication to avoid displaying the same message twice
Channel Management:
- Fetch all channel slots even if you encounter an empty slot
- Ideally save new channels into the first empty slot
Error Handling:
Implement timeouts for all commands (typically 5 seconds)
Handle RESP_CODE_ERR responses appropriately

Troubleshooting

Connection Issues

Device not found: Ensure device is powered on and advertising
Connection timeout: Check Bluetooth permissions and device proximity
GATT errors: Ensure proper service/characteristic discovery

Command Issues

No response: Verify notifications are enabled, check connection state
Error responses: Verify command format and check error code
Timeout: Increase timeout value or try again

Message Issues

Messages not received: Poll GET_MESSAGE command periodically
Duplicate messages: Implement message deduplication using timestamp/content as a unique id
Message truncation: Send long messages as separate shorter messages

Companion Protocol

Official Libraries

Important Security Note

Table of Contents

BLE Connection

Service and Characteristics

Connection Steps

BLE Write Type

MTU (Maximum Transmission Unit)

Command Sequencing

Command Queue Management

Packet Structure

Commands

Bluetooth LoRa mOTA source

1. App Start

2. Device Query

3. Get Channel Info

4. Set Channel

5. Send Channel Message

6. Send Channel Data Datagram

Registered data_type values

Receive Channel Data Datagram

7. Get Message

8. Get Battery and Storage

Channel Management

Channel Types

Channel Lifecycle

Message Handling

Receiving Messages

Contact Message Format

Channel Message Format

Sending Messages

Response Parsing

Terminology

Response types

Asynchronous push types

Parsing Responses

Error Codes

Frame Handling

Response Handling

Example Implementation Flow

Initialization

Creating a Private Channel

Sending a Message

Receiving Messages

Best Practices

Troubleshooting

Connection Issues

Command Issues

Message Issues

Registered `data_type` values