First

scripts/led.py

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+#!/usr/bin/env python3
+
+import struct
+import serial
+
+# -----------------------------------------------------------------------------
+# Configuration
+# -----------------------------------------------------------------------------
+
+PORT = "/dev/ttyACM1"
+BAUDRATE = 115200
+
+COMMAND_PREFIX = 0x69
+COMMAND_ID = 0x00
+
+COMMAND_LED = 2
+
+MAX_BRIGHTNESS = 255
+MIN_TRACK_SPEED = 1
+MAX_TRACK_SPEED = 1000
+
+# -----------------------------------------------------------------------------
+# LED Track
+# -----------------------------------------------------------------------------
+
+track = [
+    (MAX_BRIGHTNESS,   0,   0,   0),   # Red
+    (MAX_BRIGHTNESS, MAX_BRIGHTNESS,   0,   0),   # Yellow
+    (0,   MAX_BRIGHTNESS,   0,   0),   # Green
+    (0,   MAX_BRIGHTNESS, MAX_BRIGHTNESS,   0),   # Cyan
+    (0,     0, MAX_BRIGHTNESS,   0),   # Blue
+]
+
+# -----------------------------------------------------------------------------
+# Build payload
+# speed + length (amount of colors in track) + track (lines of colors in uint8_t)
+# -----------------------------------------------------------------------------
+
+payload = bytearray()
+
+# Track speed
+speed = 10
+payload.append((speed & 0xff))
+payload.append(((speed >> 8) & 0xff))
+
+# Number of colors
+payload.append(len(track))
+
+# Colors
+for color in track:
+    payload += struct.pack("BBBB", *color)
+
+# Length is:
+# payload
+length = len(payload)
+
+# -----------------------------------------------------------------------------
+# Build packet with placeholder CRC
+# -----------------------------------------------------------------------------
+
+packet = bytearray([
+    COMMAND_PREFIX,
+    length,
+    COMMAND_ID,
+    COMMAND_LED,
+    0x00,      # Placeholder CRC
+])
+
+packet += payload
+
+# -----------------------------------------------------------------------------
+# Calculate CRC (matches command_calculate_crc())
+#
+# Sum every byte except the CRC byte itself.
+# -----------------------------------------------------------------------------
+
+crc_sum = 0
+
+for i, byte in enumerate(packet):
+    if i == 4:      # Skip CRC field
+        continue
+    crc_sum += byte
+
+packet[4] = 0x100 - (crc_sum & 0xFF)
+# Equivalent to:
+# packet[4] = (0x100 - (crc_sum & 0xFF)) & 0xFF
+
+# -----------------------------------------------------------------------------
+# Send
+# -----------------------------------------------------------------------------
+
+print(f"Packet ({len(packet)} bytes):")
+print(packet.hex(" "))
+
+with serial.Serial(PORT, BAUDRATE, timeout=1) as ser:
+    ser.write(packet)
+    ser.flush()
+
+print("Done.")