Open source digital radio work round table and reports. Agenda for this meeting is a review of recent work for the Opulent Voice Protocol.

Demonstration Code Notes for Raspberry Pi Human-Radio Interface

Protocol Frame Structure Review

All payloads follow the same underlying frame format in OpulentVoiceProtocol.create_frame() method.

Header: 14 bytes (sync word + station ID + type + sequence + length + reserved)

Payload: Variable length data specific to each message type

Payload Type Creation Methods

1. Audio Payloads (Highest Priority)

def create_audio_frame(self, opus_packet):
return self.create_frame(self.FRAME_TYPE_AUDIO, opus_packet)

Source: OPUS-encoded audio data from the microphone

Processing: Raw audio → PyAudio → OPUS encoder → binary packet

Priority: Immediate transmission (bypasses queue)

Usage: Real-time voice during PTT active

2. Text Payloads (Chat Messages)

def create_text_frame(self, text_data):
if isinstance(text_data, str):
text_data = text_data.encode(‘utf-8’)
return self.create_frame(self.FRAME_TYPE_TEXT, text_data)

Source: Terminal chat input or buffered messages

Processing: String → UTF-8 encoding → binary payload

Priority: Queued (waits for PTT release)

Usage: Terminal chat interface

3. Control Payloads (System Commands)

def create_control_frame(self, control_data):
if isinstance(control_data, str):
control_data = control_data.encode(‘utf-8’)
return self.create_frame(self.FRAME_TYPE_CONTROL, control_data)

Source: System events like “PTT_START”, “PTT_STOP”

Processing: String → UTF-8 encoding → binary payload

Priority: High priority (queued but processed quickly)

Usage: PTT state changes, system notifications

4. Data Payloads (File Transfer)

def create_data_frame(self, data):
return self.create_frame(self.FRAME_TYPE_DATA, data)

Source: Raw binary data for file transfers

Processing: Binary data passed through unchanged

Priority: Lowest priority (queued)

Usage: Future file transfer capabilities

Message Flow Architecture:

The code uses a domain-driven approach with clear separation of data types.

Message Creation Flow:

Input Source → Different interfaces (GPIO, terminal, system events)
Domain Logic → ChatManager and MessagePriorityQueue handle routing
Protocol Layer → OpulentVoiceProtocol creates properly formatted frames
Transport Layer → NetworkTransmitter handles UDP delivery

Priority Queue System (Proposed)
class MessageType(Enum):

VOICE = (1, “VOICE”)  # Immediate transmission
CONTROL = (2, “CONTROL”)   # High priority queue
TEXT = (3, “TEXT”)     # Normal priority queue
DATA = (4, “DATA”)     # Low priority queue