feat(07-03): add FrameAssembler to firmware/protocol.py

- Add FrameAssembler class for multi-packet DNRGB reassembly
- 200ms timeout discards stale partial frames
- feed() returns complete frame list when all expected pixels received
- reset() clears buffer manually

firmware/protocol.py

@@ -0,0 +1,137 @@
+import struct
+
+# Protocol type bytes (first byte of UDP packet)
+PROTO_DRGB = 0x02
+PROTO_DRGBW = 0x03
+PROTO_DNRGB = 0x04
+PROTO_ANIM_CMD = 0xAC
+
+ANIMATION_NAMES = {
+    0: 'solid_color', 1: 'chase', 2: 'pulse',
+    3: 'rainbow', 4: 'strobe', 5: 'color_wipe', 6: 'fire'
+}
+
+
+def classify_packet(data):
+    """Return packet type string from first byte, or None if unknown."""
+    if not data:
+        return None
+    b = data[0]
+    if b == PROTO_DRGB:
+        return 'drgb'
+    elif b == PROTO_DRGBW:
+        return 'drgbw'
+    elif b == PROTO_DNRGB:
+        return 'dnrgb'
+    elif b == PROTO_ANIM_CMD:
+        return 'anim_cmd'
+    return None
+
+
+def parse_drgb(data):
+    """Parse DRGB packet -> list of (R,G,B) tuples.
+
+    Format: [0x02][timeout][R0][G0][B0]...[Rn][Gn][Bn]
+    """
+    n = (len(data) - 2) // 3
+    pixels = []
+    for i in range(n):
+        off = 2 + i * 3
+        pixels.append((data[off], data[off + 1], data[off + 2]))
+    return pixels
+
+
+def parse_drgbw(data):
+    """Parse DRGBW packet -> list of (R,G,B,W) tuples.
+
+    Format: [0x03][timeout][R0][G0][B0][W0]...[Rn][Gn][Bn][Wn]
+    """
+    n = (len(data) - 2) // 4
+    pixels = []
+    for i in range(n):
+        off = 2 + i * 4
+        pixels.append((data[off], data[off + 1], data[off + 2], data[off + 3]))
+    return pixels
+
+
+def parse_dnrgb(data):
+    """Parse DNRGB packet -> (start_index, list of (R,G,B) tuples).
+
+    Format: [0x04][timeout][start_hi][start_lo][R0][G0][B0]...
+    Start index is big-endian uint16.
+    """
+    start_index = struct.unpack('>H', data[2:4])[0]
+    n = (len(data) - 4) // 3
+    pixels = []
+    for i in range(n):
+        off = 4 + i * 3
+        pixels.append((data[off], data[off + 1], data[off + 2]))
+    return start_index, pixels
+
+
+def parse_animation_cmd(data):
+    """Parse animation command packet -> dict with animation name and params.
+
+    Format (16 bytes, big-endian):
+      Byte 0:     0xAC marker
+      Byte 1:     version (1)
+      Byte 2:     animation type ID (0-6)
+      Byte 3:     flags (bit 0 = reverse)
+      Bytes 4-7:  speed (float32 big-endian)
+      Bytes 8-10: primary color R, G, B
+      Bytes 11-13: background color R, G, B
+      Byte 14:    white channel
+      Byte 15:    density/size/cooling
+    """
+    if len(data) < 16 or data[0] != PROTO_ANIM_CMD:
+        return None
+    anim_id = data[2]
+    flags = data[3]
+    speed = struct.unpack('>f', data[4:8])[0]
+    anim_name = ANIMATION_NAMES.get(anim_id)
+    if anim_name is None:
+        return None
+    return {
+        'animation': anim_name,
+        'speed': speed,
+        'color': (data[8], data[9], data[10]),
+        'bg_color': (data[11], data[12], data[13]),
+        'white': data[14],
+        'density': data[15],
+        'reverse': bool(flags & 0x01),
+    }
+
+
+class FrameAssembler:
+    """Reassembles multi-packet DNRGB frames.
+
+    For 300-LED strips, frames fit in one packet so reassembly never triggers.
+    Implemented for completeness and future strip sizes.
+    """
+
+    def __init__(self, expected_count):
+        self.expected_count = expected_count
+        self._buf = {}  # start_index -> list of (R,G,B)
+        self._last_ms = 0
+        self._TIMEOUT_MS = 200
+
+    def feed(self, start_index, pixels, now_ms):
+        """Feed a DNRGB chunk. Returns complete frame list or None."""
+        # Timeout: discard stale partial frames
+        if self._buf and (now_ms - self._last_ms) > self._TIMEOUT_MS:
+            self._buf.clear()
+
+        self._last_ms = now_ms
+
+        for i, px in enumerate(pixels):
+            self._buf[start_index + i] = px
+
+        if len(self._buf) >= self.expected_count:
+            frame = [self._buf.get(i, (0, 0, 0)) for i in range(self.expected_count)]
+            self._buf.clear()
+            return frame
+
+        return None
+
+    def reset(self):
+        self._buf.clear()