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Update companion protocol documentation and enhance data type definitions for clarity

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zjs81
2026-04-24 04:24:20 -07:00
parent 5372388e6e
commit b705d5489f
2 changed files with 109 additions and 29 deletions
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docs/companion_protocol.md
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@@ -283,32 +283,101 @@ Bytes 7+: Message Text (UTF-8, variable length)
### 6. Send Channel Data Datagram
**Purpose**: Send binary datagram data to a channel.
**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
Bytes 1-2: Data Type (`data_type`, 16-bit little-endian)
Byte 3: Channel Index (0-7)
Bytes 4+: Binary payload bytes (variable length)
Byte 1: Channel Index (0-7)
Byte 2: Path Length (0xFF = flood, otherwise actual path length)
Bytes 3 .. 2+path_len: Path (omitted when path_len == 0xFF)
Next 2 bytes (little-endian): Data Type (`data_type`, uint16)
Remaining bytes: Binary payload (variable length)
```
**Example** (flood, `DATA_TYPE_DEV`, payload `A1 B2 C3`, channel 1):
```
3E 01 FF FF FF A1 B2 C3
```
**Data Type / Transport Mapping**:
- `0x0000` is invalid for this command.
- `0x0000` (`DATA_TYPE_RESERVED`) is invalid and rejected with `PACKET_ERROR`.
- `0xFFFF` (`DATA_TYPE_DEV`) is the developer namespace for experimenting and developing apps.
- Other non-zero values can be used as assigned application/community namespaces.
**Note**: Applications that need a timestamp should encode it inside the binary payload.
- Values `0x0001`–`0xFFFE` are available for registered application/community namespaces. See the [Registered data_type values](#registered-data_type-values) table below.
**Limits**:
- Maximum payload length is `163` bytes.
- Larger payloads are rejected with `PACKET_ERROR`.
- Maximum payload length is `MAX_CHANNEL_DATA_LENGTH = MAX_FRAME_SIZE - 9 = 163` bytes.
- Larger payloads are rejected with `PACKET_ERROR` (`ERR_CODE_ILLEGAL_ARG`).
**Response**: `PACKET_OK` (0x00) on success
**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](#receive-channel-data-datagram).
#### Registered `data_type` values
Declared in `src/helpers/TxtDataHelpers.h`. These values have agreed-upon payload schemas so different client apps on the same channel can interoperate.
| Value | Constant | Purpose | Payload schema |
|--------|----------------------|---------------------------------------------|--------------------------------------------------------------------------------------------------------|
| 0x0000 | `DATA_TYPE_RESERVED` | Reserved; invalid on send | — |
| 0x0001 | `DATA_TYPE_SMAZ_TEXT`| Raw SMAZ-compressed UTF-8 text | `[sender_name_len: u8][sender_name: UTF-8 × sender_name_len][smaz_bytes: remaining]` |
| 0x0002 | `DATA_TYPE_GIPHY_GIF`| Giphy GIF id (avoids base64 tax) | `[sender_name_len: u8][sender_name: UTF-8 × sender_name_len][giphy_id: ASCII, remaining]` |
| 0x0003 | `DATA_TYPE_REACTION` | Emoji reaction targeting a prior message | `[target_hash: 2 bytes LE][emoji_index: u8][sender_name_len: u8][sender_name: UTF-8 × sender_name_len]` |
| 0xFFFF | `DATA_TYPE_DEV` | Developer/experimental namespace | Application-defined |
The firmware does not inspect the payload contents — `data_type` is transported opaquely, and the schemas above are a client-side contract between cooperating apps.
To request a new registered value, submit a PR adding a `#define` to `TxtDataHelpers.h` and a row to this table.
---
### 6. Get Message
### 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 ×4 — divide by 4.0 to recover dB)
Bytes 2-3: Reserved
Byte 4: Channel Index (0-7)
Byte 5: Path Length (actual path when flooded, otherwise 0xFF)
Bytes 6-7: Data Type (uint16 little-endian)
Byte 8: Data Length
Bytes 9 .. 8+data_len: Payload
```
**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**:
```python
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.
@@ -325,13 +394,14 @@ Byte 0: 0x0A
**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.
---
### 7. Get Battery and Storage
### 8. Get Battery and Storage
**Purpose**: Query device battery voltage and storage usage.
@@ -527,6 +597,15 @@ Use the `SEND_CHANNEL_MESSAGE` command (see [Commands](#commands)).
## 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.
### Packet Types
| Value | Name | Description |
@@ -547,6 +626,7 @@ Use the `SEND_CHANNEL_MESSAGE` command (see [Commands](#commands)).
| 0x10 | PACKET_CONTACT_MSG_RECV_V3 | Contact message (V3 with SNR) |
| 0x11 | PACKET_CHANNEL_MSG_RECV_V3 | Channel message (V3 with SNR) |
| 0x12 | PACKET_CHANNEL_INFO | Channel information |
| 0x1B | PACKET_CHANNEL_DATA_RECV | Channel data datagram |
| 0x80 | PACKET_ADVERTISEMENT | Advertisement packet |
| 0x82 | PACKET_ACK | Acknowledgment |
| 0x83 | PACKET_MESSAGES_WAITING | Messages waiting notification |
@@ -718,22 +798,18 @@ Bytes 1-6: ACK Code (6 bytes, hex)
### Error Codes
**PACKET_ERROR** (0x01) may include an error code in byte 1:
`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`:
| Error Code | Description |
|------------|-------------|
| 0x00 | Generic error (no specific code) |
| 0x01 | Invalid command |
| 0x02 | Invalid parameter |
| 0x03 | Channel not found |
| 0x04 | Channel already exists |
| 0x05 | Channel index out of range |
| 0x06 | Secret mismatch |
| 0x07 | Message too long |
| 0x08 | Device busy |
| 0x09 | Not enough storage |
| 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.
**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
@@ -765,7 +841,8 @@ BLE implementations enqueue and deliver one protocol frame per BLE write/notific
- `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`, or `PACKET_NO_MORE_MSGS`
- `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`
4. **Timeout Handling**:

3
src/helpers/TxtDataHelpers.h
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@@ -7,6 +7,9 @@
#define TXT_TYPE_CLI_DATA 1 // a CLI command
#define TXT_TYPE_SIGNED_PLAIN 2 // plain text, signed by sender
#define DATA_TYPE_RESERVED 0x0000 // reserved for future use
#define DATA_TYPE_SMAZ_TEXT 0x0001 // raw SMAZ-compressed UTF-8 text meshcore-open Flutter client.
#define DATA_TYPE_GIPHY_GIF 0x0002 // ASCII Giphy GIF id meshcore-open Flutter client.
#define DATA_TYPE_REACTION 0x0003 // 2-byte target message hash + 1-byte emoji index meshcore-open Flutter client.
#define DATA_TYPE_DEV 0xFFFF // developer namespace for experimenting with group/channel datagrams and building apps
class StrHelper {