python backend arduino service
This commit is contained in:
Mikkeli Matlock
175
pi/backend/arduino_service.py
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175
pi/backend/arduino_service.py
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"""Arduino service - connects to Arduino Nano via serial, buffers telemetry."""
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import json
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import re
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import threading
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import time
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from collections import deque
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from typing import Any
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# pyserial for UART communication
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try:
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import serial
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except ImportError:
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serial = None # Allow import without pyserial for testing structure
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class ArduinoService:
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"""Threaded Arduino serial reader with buffering and auto-reconnect."""
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# Regex patterns for legacy text protocol
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PATTERNS = {
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"voltage": re.compile(r"V_bat:\s*(\d+\.?\d*)V?", re.IGNORECASE),
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"rpm": re.compile(r"RPM:\s*(\d+)", re.IGNORECASE),
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"eng_temp": re.compile(r"ENG:\s*(\d+)C?", re.IGNORECASE),
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"gear": re.compile(r"GEAR:\s*(\d+)", re.IGNORECASE),
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}
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def __init__(
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self,
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port: str = "/dev/ttyUSB0",
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baudrate: int = 115200,
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buffer_size: int = 100,
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):
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self.port = port
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self.baudrate = baudrate
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self.buffer_size = buffer_size
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self._buffer: deque[dict[str, Any]] = deque(maxlen=buffer_size)
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self._latest: dict[str, Any] = {}
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self._connected = False
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self._running = False
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self._thread: threading.Thread | None = None
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self._lock = threading.Lock()
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@property
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def connected(self) -> bool:
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return self._connected
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def get_latest(self) -> dict[str, Any]:
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"""Get most recent telemetry values."""
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with self._lock:
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return self._latest.copy() if self._latest else {"error": "no data"}
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def get_buffer(self) -> list[dict[str, Any]]:
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"""Get buffered telemetry history."""
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with self._lock:
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return list(self._buffer)
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def start(self):
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"""Start background serial reader thread."""
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if self._running:
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return
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self._running = True
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self._thread = threading.Thread(target=self._reader_loop, daemon=True)
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self._thread.start()
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def stop(self):
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"""Stop background reader."""
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self._running = False
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if self._thread:
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self._thread.join(timeout=2.0)
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def _reader_loop(self):
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"""Main reader loop with reconnection logic."""
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while self._running:
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try:
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self._connect_and_read()
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except Exception as e:
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self._connected = False
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print(f"[Arduino] Connection error: {e}, retrying in 5s...")
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time.sleep(5)
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def _connect_and_read(self):
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"""Connect to Arduino serial and read data."""
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if serial is None:
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# Stub mode - no pyserial installed
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print("[Arduino] pyserial not installed, running in stub mode")
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self._stub_mode()
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return
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try:
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ser = serial.Serial(
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port=self.port,
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baudrate=self.baudrate,
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timeout=1.0,
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)
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except serial.SerialException as e:
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print(f"[Arduino] Cannot open {self.port}: {e}, falling back to stub mode")
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self._stub_mode()
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return
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try:
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self._connected = True
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print(f"[Arduino] Connected to {self.port} @ {self.baudrate} baud")
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while self._running:
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try:
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line = ser.readline().decode("utf-8", errors="ignore").strip()
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if not line:
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continue
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data = self._parse_line(line)
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if data:
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data["time"] = time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime())
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with self._lock:
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# Merge new values into latest (preserve old values for partial updates)
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for key, val in data.items():
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if val is not None:
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self._latest[key] = val
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self._latest["time"] = data["time"]
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self._buffer.append(self._latest.copy())
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except serial.SerialException as e:
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print(f"[Arduino] Serial error: {e}")
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break
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finally:
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self._connected = False
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ser.close()
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def _parse_line(self, line: str) -> dict[str, Any] | None:
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"""Parse a line from Arduino - JSON first, fallback to regex.
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JSON format: {"v":12.45,"rpm":4500,"eng":85,"gear":3}
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Legacy text: V_bat: 12.45V
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"""
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# Try JSON first (production format)
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try:
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obj = json.loads(line)
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return {
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"voltage": obj.get("v"),
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"rpm": obj.get("rpm"),
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"eng_temp": obj.get("eng"),
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"gear": obj.get("gear"),
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}
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except json.JSONDecodeError:
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pass
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# Fallback to regex for legacy text protocol
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result = {}
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for key, pattern in self.PATTERNS.items():
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match = pattern.search(line)
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if match:
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val = match.group(1)
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result[key] = float(val) if "." in val else int(val)
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return result if result else None
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def _stub_mode(self):
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"""Fake data for testing without Arduino connected."""
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import random
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while self._running:
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self._connected = True
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data = {
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"time": time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime()),
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"voltage": round(12.0 + random.uniform(-0.5, 0.8), 2),
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"rpm": random.randint(800, 6000) if random.random() > 0.3 else None,
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"eng_temp": random.randint(60, 95),
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"gear": random.randint(1, 6) if random.random() > 0.2 else 0, # 0 = neutral
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}
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with self._lock:
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self._latest = data
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self._buffer.append(data)
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time.sleep(0.5) # 2Hz stub updates
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