feat(07-01): add firmware scaffold — boot.py, config.json, led_driver.py, protocol tests

- firmware/boot.py: WiFi connection on startup (MicroPython boot sequence)
- firmware/config.json: default device config with all 9 fields (ssid, password, led_count, strip_type, led_pin, spi_id, spi_clk_pin, spi_dat_pin, udp_port)
- firmware/led_driver.py: NeoPixelStrip (SK6812 RGBW) and WS2801Strip (RGB SPI) with unified interface (write_rgb, write_rgbw, fill, clear)
- tests/test_firmware_protocol.py: 21 host-side tests for round-trip protocol parsing (DRGB, DRGBW, DNRGB, animation_cmd)

firmware/boot.py

@@ -0,0 +1,38 @@
+import network
+import time
+import json
+
+
+def load_config():
+    try:
+        with open('config.json') as f:
+            return json.load(f)
+    except OSError:
+        print('[boot] config.json not found, using defaults')
+        return {
+            'ssid': 'MyWiFi', 'password': 'secret',
+            'led_count': 300, 'strip_type': 'sk6812',
+            'led_pin': 5, 'spi_id': 1, 'udp_port': 21324
+        }
+
+
+def connect_wifi(ssid, password, timeout=15):
+    wlan = network.WLAN(network.STA_IF)
+    wlan.active(True)
+    if wlan.isconnected():
+        print('[boot] Already connected:', wlan.ifconfig()[0])
+        return wlan
+    print('[boot] Connecting to', ssid, '...')
+    wlan.connect(ssid, password)
+    start = time.time()
+    while not wlan.isconnected():
+        if time.time() - start > timeout:
+            print('[boot] WiFi timeout after', timeout, 'seconds')
+            return wlan
+        time.sleep(0.5)
+    print('[boot] Connected:', wlan.ifconfig()[0])
+    return wlan
+
+
+config = load_config()
+wlan = connect_wifi(config['ssid'], config['password'])

firmware/config.json

@@ -0,0 +1,11 @@
+{
+  "ssid": "MyWiFi",
+  "password": "secret",
+  "led_count": 300,
+  "strip_type": "sk6812",
+  "led_pin": 5,
+  "spi_id": 1,
+  "spi_clk_pin": 18,
+  "spi_dat_pin": 23,
+  "udp_port": 21324
+}

firmware/led_driver.py

@@ -0,0 +1,87 @@
+class NeoPixelStrip:
+    """SK6812 RGBW driver using built-in neopixel module."""
+
+    def __init__(self, pin_num, led_count):
+        import neopixel
+        from machine import Pin
+        self.np = neopixel.NeoPixel(Pin(pin_num), led_count, bpp=4, timing=1)
+        self.led_count = led_count
+
+    def write_rgb(self, pixels):
+        """Write list of (R,G,B) tuples. W channel set to 0."""
+        for i, (r, g, b) in enumerate(pixels):
+            if i >= self.led_count:
+                break
+            self.np[i] = (r, g, b, 0)
+        self.np.write()
+
+    def write_rgbw(self, pixels):
+        """Write list of (R,G,B,W) tuples."""
+        for i, (r, g, b, w) in enumerate(pixels):
+            if i >= self.led_count:
+                break
+            self.np[i] = (r, g, b, w)
+        self.np.write()
+
+    def fill(self, r, g, b, w=0):
+        """Fill all pixels with one color."""
+        self.np.fill((r, g, b, w))
+        self.np.write()
+
+    def clear(self):
+        self.fill(0, 0, 0, 0)
+
+
+class WS2801Strip:
+    """WS2801 RGB driver using SPI — no external library needed."""
+
+    def __init__(self, spi_id, clk_pin, dat_pin, led_count):
+        from machine import SPI, Pin
+        self.spi = SPI(spi_id, baudrate=1000000, polarity=0, phase=0,
+                       sck=Pin(clk_pin), mosi=Pin(dat_pin))
+        self.led_count = led_count
+        self._buf = bytearray(led_count * 3)
+
+    def write_rgb(self, pixels):
+        """Write list of (R,G,B) tuples."""
+        for i, (r, g, b) in enumerate(pixels):
+            if i >= self.led_count:
+                break
+            off = i * 3
+            self._buf[off] = r
+            self._buf[off + 1] = g
+            self._buf[off + 2] = b
+        self.spi.write(self._buf)
+
+    def write_rgbw(self, pixels):
+        """Write RGBW tuples — W channel is discarded (WS2801 is RGB only)."""
+        for i, (r, g, b, _w) in enumerate(pixels):
+            if i >= self.led_count:
+                break
+            off = i * 3
+            self._buf[off] = r
+            self._buf[off + 1] = g
+            self._buf[off + 2] = b
+        self.spi.write(self._buf)
+
+    def fill(self, r, g, b, w=0):
+        for i in range(self.led_count):
+            off = i * 3
+            self._buf[off] = r
+            self._buf[off + 1] = g
+            self._buf[off + 2] = b
+        self.spi.write(self._buf)
+
+    def clear(self):
+        self.fill(0, 0, 0)
+
+
+def create_strip(config):
+    """Factory: create the right strip driver from config dict."""
+    if config['strip_type'] == 'sk6812':
+        return NeoPixelStrip(config['led_pin'], config['led_count'])
+    elif config['strip_type'] == 'ws2801':
+        return WS2801Strip(config['spi_id'], config.get('spi_clk_pin', 18),
+                           config.get('spi_dat_pin', 23), config['led_count'])
+    else:
+        raise ValueError('Unknown strip_type: ' + config['strip_type'])