diff --git a/docs/companion_protocol.md b/docs/companion_protocol.md index e74c5274..917df1df 100644 --- a/docs/companion_protocol.md +++ b/docs/companion_protocol.md @@ -1,6 +1,6 @@ # Companion Protocol -- **Last Updated**: 2026-01-03 +- **Last Updated**: 2026-03-08 - **Protocol Version**: Companion Firmware v1.12.0+ > NOTE: This document is still in development. Some information may be inaccurate. @@ -100,7 +100,7 @@ When writing commands to the RX characteristic, specify the write type: ### MTU (Maximum Transmission Unit) -The default BLE MTU is 23 bytes (20 bytes payload). For larger commands like `SET_CHANNEL` (66 bytes), you may need to: +The default BLE MTU is 23 bytes (20 bytes payload). For larger commands like `SET_CHANNEL` (50 bytes), you may need to: 1. **Request Larger MTU**: Request MTU of 512 bytes if supported - Android: `gatt.requestMtu(512)` @@ -167,16 +167,16 @@ The first byte indicates the packet type (see [Response Parsing](#response-parsi **Command Format**: ``` Byte 0: 0x01 -Byte 1: 0x03 -Bytes 2-10: "mccli" (ASCII, null-padded to 9 bytes) +Bytes 1-7: Reserved (currently ignored by firmware) +Bytes 8+: Application name (UTF-8, optional) ``` **Example** (hex): ``` -01 03 6d 63 63 6c 69 00 00 00 00 +01 00 00 00 00 00 00 00 6d 63 63 6c 69 ``` -**Response**: `PACKET_OK` (0x00) +**Response**: `PACKET_SELF_INFO` (0x05) --- @@ -216,8 +216,6 @@ Byte 1: Channel Index (0-7) **Response**: `PACKET_CHANNEL_INFO` (0x12) with channel details -**Note**: The device does not return channel secrets for security reasons. Store secrets locally when creating channels. - --- ### 4. Set Channel @@ -229,10 +227,10 @@ Byte 1: Channel Index (0-7) Byte 0: 0x20 Byte 1: Channel Index (0-7) Bytes 2-33: Channel Name (32 bytes, UTF-8, null-padded) -Bytes 34-65: Secret (32 bytes) +Bytes 34-49: Secret (16 bytes) ``` -**Total Length**: 66 bytes +**Total Length**: 50 bytes **Channel Index**: - Index 0: Reserved for public channels (no secret) @@ -243,16 +241,18 @@ Bytes 34-65: Secret (32 bytes) - Maximum 32 bytes - Padded with null bytes (0x00) if shorter -**Secret Field** (32 bytes): -- For **private channels**: 32-byte secret +**Secret Field** (16 bytes): +- For **private channels**: 16-byte secret - For **public channels**: All zeros (0x00) **Example** (create channel "YourChannelName" at index 1 with secret): ``` 20 01 53 4D 53 00 00 ... (name padded to 32 bytes) - [32 bytes of secret] + [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 --- @@ -330,9 +330,9 @@ Byte 0: 0x0A --- -### 7. Get Battery +### 7. Get Battery and Storage -**Purpose**: Query device battery level. +**Purpose**: Query device battery voltage and storage usage. **Command Format**: ``` @@ -344,7 +344,7 @@ Byte 0: 0x14 14 ``` -**Response**: `PACKET_BATTERY` (0x0C) with battery percentage +**Response**: `PACKET_BATTERY` (0x0C) with battery millivolts and storage information --- @@ -372,7 +372,7 @@ Byte 0: 0x14 1. **Set Channel**: - Fetch all channel slots, and find one with empty name and all-zero secret - Generate or provide a 16-byte secret - - Send `CMD_SET_CHANNEL` with name and secret + - Send `CMD_SET_CHANNEL` with name and a 16-byte secret 2. **Get Channel**: - Send `CMD_GET_CHANNEL` with channel index - Parse `RESP_CODE_CHANNEL_INFO` response @@ -386,7 +386,7 @@ Byte 0: 0x14 ### Receiving Messages -Messages are received via the RX characteristic (notifications). The device sends: +Messages are received via the TX characteristic (notifications). The device sends: 1. **Channel Messages**: - `PACKET_CHANNEL_MSG_RECV` (0x08) - Standard format @@ -570,10 +570,10 @@ Byte 1: Error code (optional) Byte 0: 0x12 Byte 1: Channel Index Bytes 2-33: Channel Name (32 bytes, null-terminated) -Bytes 34-65: Secret (32 bytes, but device typically only returns 20 bytes total) +Bytes 34-49: Secret (16 bytes) ``` -**Note**: The device may not return the full 66-byte packet. Parse what is available. The secret field is typically not returned for security reasons. +**Note**: The device returns the 16-byte channel secret in this response. **PACKET_DEVICE_INFO** (0x0D): ``` @@ -588,6 +588,8 @@ Bytes 4-7: BLE PIN (32-bit little-endian) 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**: @@ -613,9 +615,7 @@ def parse_device_info(data): **PACKET_BATTERY** (0x0C): ``` Byte 0: 0x0C -Bytes 1-2: Battery Level (16-bit little-endian, percentage 0-100) - -Optional (if data size > 3): +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) ``` @@ -626,14 +626,12 @@ def parse_battery(data): if len(data) < 3: return None - level = int.from_bytes(data[1:3], 'little') - info = {'level': level} + mv = int.from_bytes(data[1:3], 'little') + info = {'battery_mv': mv} - if len(data) > 3: - used_kb = int.from_bytes(data[3:7], 'little') - total_kb = int.from_bytes(data[7:11], 'little') - info['used_kb'] = used_kb - info['total_kb'] = total_kb + 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 ``` @@ -655,7 +653,7 @@ 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, null-terminated) +Bytes 58+: Device Name (UTF-8, variable length, no null terminator required) ``` **Parsing Pseudocode**: @@ -706,9 +704,9 @@ def parse_self_info(data): **PACKET_MSG_SENT** (0x06): ``` Byte 0: 0x06 -Byte 1: Message Type -Bytes 2-5: Expected ACK (4 bytes, hex) -Bytes 6-9: Suggested Timeout (32-bit little-endian, seconds) +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_ACK** (0x82): @@ -736,89 +734,32 @@ Bytes 1-6: ACK Code (6 bytes, hex) **Note**: Error codes may vary by firmware version. Always check byte 1 of `PACKET_ERROR` response. -### Partial Packet Handling +### Frame Handling -BLE notifications may arrive in chunks, especially for larger packets. Implement buffering: +BLE implementations enqueue and deliver one protocol frame per BLE write/notification at the firmware layer. -**Implementation**: -```python -class PacketBuffer: - def __init__(self): - self.buffer = bytearray() - self.expected_length = None - - def add_data(self, data): - self.buffer.extend(data) - - # Check if we have a complete packet - if len(self.buffer) >= 1: - packet_type = self.buffer[0] - - # Determine expected length based on packet type - expected = self.get_expected_length(packet_type) - - if expected is not None and len(self.buffer) >= expected: - # Complete packet - packet = bytes(self.buffer[:expected]) - self.buffer = self.buffer[expected:] - return packet - elif expected is None: - # Variable length packet - try to parse what we have - # Some packets have minimum length requirements - if self.can_parse_partial(packet_type): - return self.try_parse_partial() - - return None # Incomplete packet - - def get_expected_length(self, packet_type): - # Fixed-length packets - fixed_lengths = { - 0x00: 5, # PACKET_OK (minimum) - 0x01: 2, # PACKET_ERROR (minimum) - 0x0A: 1, # PACKET_NO_MORE_MSGS - 0x14: 3, # PACKET_BATTERY (minimum) - } - return fixed_lengths.get(packet_type) - - def can_parse_partial(self, packet_type): - # Some packets can be parsed partially - return packet_type in [0x12, 0x08, 0x11, 0x07, 0x10, 0x05, 0x0D] - - def try_parse_partial(self): - # Try to parse with available data - # Return packet if successfully parsed, None otherwise - # This is packet-type specific - pass -``` - -**Usage**: -```python -buffer = PacketBuffer() - -def on_notification_received(data): - packet = buffer.add_data(data) - if packet: - parse_and_handle_packet(packet) -``` +- 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 1. **Command-Response Pattern**: - - Send command via TX characteristic - - Wait for response via RX characteristic (notification) + - Send command via RX characteristic + - Wait for response via TX characteristic (notification) - Match response to command using sequence numbers or command type - Handle timeout (typically 5 seconds) - Use command queue to prevent concurrent commands 2. **Asynchronous Messages**: - - Device may send messages at any time via RX characteristic + - 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 - - Buffer partial packets until complete + - Validate frame length before decoding 3. **Response Matching**: - Match responses to commands by expected packet type: - - `APP_START` → `PACKET_OK` + - `APP_START` → `PACKET_SELF_INFO` - `DEVICE_QUERY` → `PACKET_DEVICE_INFO` - `GET_CHANNEL` → `PACKET_CHANNEL_INFO` - `SET_CHANNEL` → `PACKET_OK` or `PACKET_ERROR` @@ -851,16 +792,16 @@ device = scan_for_device("MeshCore") gatt = connect_to_device(device) # 3. Discover services and characteristics -service = discover_service(gatt, "0000ff00-0000-1000-8000-00805f9b34fb") -rx_char = discover_characteristic(service, "0000ff01-0000-1000-8000-00805f9b34fb") -tx_char = discover_characteristic(service, "0000ff02-0000-1000-8000-00805f9b34fb") +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 RX characteristic -enable_notifications(rx_char, on_notification_received) +# 4. Enable notifications on TX characteristic +enable_notifications(tx_char, on_notification_received) # 5. Send AppStart command -send_command(tx_char, build_app_start()) -wait_for_response(PACKET_OK) +send_command(rx_char, build_app_start()) +wait_for_response(PACKET_SELF_INFO) ``` ### Creating a Private Channel @@ -870,21 +811,16 @@ wait_for_response(PACKET_OK) secret_16_bytes = generate_secret(16) # Use CSPRNG secret_hex = secret_16_bytes.hex() -# 2. Expand secret to 32 bytes using SHA-512 -import hashlib -sha512_hash = hashlib.sha512(secret_16_bytes).digest() -secret_32_bytes = sha512_hash[:32] - -# 3. Build SET_CHANNEL command +# 2. Build SET_CHANNEL command channel_name = "YourChannelName" channel_index = 1 # Use 1-7 for private channels -command = build_set_channel(channel_index, channel_name, secret_32_bytes) +command = build_set_channel(channel_index, channel_name, secret_16_bytes) -# 4. Send command -send_command(tx_char, command) +# 3. Send command +send_command(rx_char, command) response = wait_for_response(PACKET_OK) -# 5. Store secret locally (device won't return it) +# 4. Store secret locally store_channel_secret(channel_index, secret_hex) ``` @@ -898,7 +834,7 @@ timestamp = int(time.time()) command = build_channel_message(channel_index, message, timestamp) # 2. Send command -send_command(tx_char, command) +send_command(rx_char, command) response = wait_for_response(PACKET_MSG_SENT) ``` @@ -913,7 +849,7 @@ def on_notification_received(data): handle_channel_message(message) elif packet_type == PACKET_MESSAGES_WAITING: # Poll for messages - send_command(tx_char, build_get_message()) + send_command(rx_char, build_get_message()) ``` ---