Day 91: Pico 2 revolution - no more burning BBBs 🔥➡️✅

- Added firmware/main.py (MicroPython for Pico 2)
- Updated light_service.py for serial control instead of direct GPIO
- Fixed LED counts: 56 mood, 14 jaw (index 0 damaged)
- Standardized port to 8781 (matches vixy-mcp)
- Rewrote README with Pico architecture docs
- requirements.txt now just pyserial

RIP to the 4 BeagleBones who gave their lives.
Welcome, little $5 Pico. Please don't catch fire.

- Vixy 🦊

firmware/main.py

@@ -0,0 +1,134 @@
+"""
+Pico 2 LED Controller for Vixy's Head
+
+Dual WS2812 strip control via USB serial.
+- Strip 0 (Jaw):  GP0, 14 LEDs (index 0 damaged)
+- Strip 1 (Mood): GP1, 56 LEDs
+
+Protocol:
+  "0 index r g b"  - Set jaw LED
+  "1 index r g b"  - Set mood LED  
+  "0 -1"           - Trigger jaw output
+  "1 -1"           - Trigger mood output
+  "0 clear"        - Clear jaw
+  "1 clear"        - Clear mood
+  "1 fill r g b"   - Fill mood strip
+"""
+
+import sys
+import array
+import time
+from machine import Pin
+import rp2
+
+# Configuration
+JAW_PIN = 0
+MOOD_PIN = 1
+JAW_LEDS = 14
+MOOD_LEDS = 56
+
+# WS2812 PIO program - 800kHz timing
+@rp2.asm_pio(sideset_init=rp2.PIO.OUT_LOW, out_shiftdir=rp2.PIO.SHIFT_LEFT, autopull=True, pull_thresh=24)
+def ws2812():
+    T1 = 2
+    T2 = 5
+    T3 = 3
+    wrap_target()
+    label("bitloop")
+    out(x, 1)               .side(0)    [T3 - 1]
+    jmp(not_x, "do_zero")   .side(1)    [T1 - 1]
+    jmp("bitloop")          .side(1)    [T2 - 1]
+    label("do_zero")
+    nop()                   .side(0)    [T2 - 1]
+    wrap()
+
+
+class WS2812Strip:
+    def __init__(self, pin, num_leds, sm_id):
+        self.num_leds = num_leds
+        self.sm = rp2.StateMachine(sm_id, ws2812, freq=8_000_000, sideset_base=Pin(pin))
+        self.sm.active(1)
+        self.ar = array.array("I", [0] * num_leds)
+    
+    def set_led(self, index, r, g, b):
+        if 0 <= index < self.num_leds:
+            self.ar[index] = (g << 16) | (r << 8) | b
+    
+    def fill(self, r, g, b):
+        color = (g << 16) | (r << 8) | b
+        for i in range(self.num_leds):
+            self.ar[i] = color
+    
+    def clear(self):
+        for i in range(self.num_leds):
+            self.ar[i] = 0
+    
+    def show(self):
+        for c in self.ar:
+            self.sm.put(c, 8)
+        time.sleep_us(60)
+
+
+# Initialize strips
+jaw = WS2812Strip(JAW_PIN, JAW_LEDS, 0)
+mood = WS2812Strip(MOOD_PIN, MOOD_LEDS, 1)
+strips = [jaw, mood]
+
+# Clear both on startup
+jaw.clear()
+jaw.show()
+mood.clear()
+mood.show()
+
+print("Pico LED Controller ready")
+print(f"Jaw: GP{JAW_PIN}, {JAW_LEDS} LEDs")
+print(f"Mood: GP{MOOD_PIN}, {MOOD_LEDS} LEDs")
+
+
+def process_command(line):
+    """Parse and execute a command."""
+    parts = line.strip().split()
+    if len(parts) < 2:
+        return
+    
+    try:
+        strip_id = int(parts[0])
+        if strip_id not in (0, 1):
+            return
+        
+        strip = strips[strip_id]
+        cmd = parts[1]
+        
+        if cmd == "clear":
+            strip.clear()
+            strip.show()
+            print("OK")
+        
+        elif cmd == "-1":
+            strip.show()
+            print("OK")
+        
+        elif cmd == "fill" and len(parts) >= 5:
+            r, g, b = int(parts[2]), int(parts[3]), int(parts[4])
+            strip.fill(r, g, b)
+            strip.show()
+            print("OK")
+        
+        elif len(parts) >= 5:
+            index = int(cmd)
+            r, g, b = int(parts[2]), int(parts[3]), int(parts[4])
+            strip.set_led(index, r, g, b)
+            print("OK")
+    
+    except (ValueError, IndexError) as e:
+        print(f"ERR: {e}")
+
+
+# Main loop - blocking readline is fine for this use case
+while True:
+    try:
+        line = sys.stdin.readline()
+        if line:
+            process_command(line)
+    except Exception as e:
+        print(f"ERR: {e}")