Tnc Data fragmentation in RadioController.send_tnc_data

src/benlink/controller.py

@@ -150,6 +150,7 @@ def handle_event(event):
 from dataclasses import dataclass
 import typing as t
 import sys
+import asyncio
 
 from .command import (
     CommandConnection,
@@ -290,14 +291,36 @@ async def rc_battery_level(self) -> int:
         return await self._conn.get_rc_battery_level()
 
     async def send_tnc_data(self, data: bytes) -> None:
-        if len(data) > 50:
-            raise ValueError("Data too long -- TODO: implement fragmentation")
-
-        await self._conn.send_tnc_data_fragment(TncDataFragment(
-            is_final_fragment=True,
-            fragment_id=0,
-            data=data
-        ))
+        chunk_size = 50
+        max_retries = 2  # Total transmissions = 1 original + 1 retry
+        total_fragments = (len(data) + chunk_size - 1) // chunk_size
+        # Send twice because first packet always fails
+        for retry in range(max_retries):
+            fragment_id = 0
+
+            for i in range(0, len(data), chunk_size):
+                chunk = data[i:i+chunk_size]
+                is_final = (i + chunk_size) >= len(data)
+
+                payload = TncDataFragment(
+                    data=chunk,
+                    fragment_id=fragment_id,
+                    is_final_fragment=is_final,
+                )
+
+                command = SendTncDataFragment(payload)
+
+                await self._conn.send_tnc_data_fragment(command)
+                if fragment_id == 0 and total_fragments > 1:
+                    # Add small delay between fragments
+                    await asyncio.sleep(0.01)
+                    await self._conn.send_tnc_data_fragment(command) # Repeat because first fragment always fails
+
+                fragment_id += 1
+
+            # Add delay between retransmissions if not the last attempt
+            if retry < max_retries - 1:
+                await asyncio.sleep(0.1)
 
     def add_event_handler(self, handler: EventHandler) -> t.Callable[[], None]:
         return self._conn.add_event_handler(handler)