Add episode recording functionality and enhance serial communication handling

- Introduced record_episode.py for capturing ESP32 IMU data and RealSense images.
- Added SwitchChangeDetector and SwitchLevelController for managing recording triggers.
- Enhanced ESP32Bridge with new methods for reading samples and latest packets.
- Updated verify.py and visualise.py to improve serial communication stability.
- Modified .gitignore to include dataset, csv, and png directories.

esp_bridge.py

@@ -3,6 +3,7 @@ import time
 import serial
 
 
+
 SYNC = b"\xA5\x5A"
 PACKET_FORMAT = "<2sBBBI10hB"
 PACKET_SIZE = struct.calcsize(PACKET_FORMAT)
@@ -35,8 +36,8 @@ class ESP32Bridge:
         port,
         baud=115200,
         timeout=0.05,
-        startup_wait=1.0,
-        safe_stop_on_close=True,
+        startup_wait=4.0,
+        safe_stop_on_close=False,
         reset_input_on_open=True,
         reset_output_on_open=True,
     ):
@@ -206,4 +207,99 @@ class ESP32Bridge:
             else:
                 yield self.read_packet()
 
-            count += 1
+            count += 1
+    def read_samples(self, seconds=None, max_samples=None, max_gap_ms=1000):
+        """
+        Read multiple packets and return flattened samples.
+
+        Suitable for visualise.py / verify.py.
+        """
+        self._require_open()
+
+        samples = []
+        bad_delta_count = 0
+        elapsed_s = 0.0
+        start = time.monotonic()
+
+        while True:
+            if seconds is not None and time.monotonic() - start >= seconds:
+                break
+
+            if max_samples is not None and len(samples) >= max_samples:
+                break
+
+            data = self.read_packet()
+
+            if self.last_t_ms is None:
+                freq_hz = 0.0
+            else:
+                delta = (data["t_ms"] - self.last_t_ms) & 0xFFFFFFFF
+                if 0 < delta <= max_gap_ms:
+                    elapsed_s += delta / 1000.0
+                    freq_hz = 1000.0 / delta
+                else:
+                    bad_delta_count += 1
+                    freq_hz = 0.0
+
+            self.last_t_ms = data["t_ms"]
+
+            sample = flatten_packet(data, elapsed_s, freq_hz)
+            samples.append(sample)
+
+        return samples, bad_delta_count
+    
+    def read_latest_packet(self, max_drain=200):
+        """
+        Return the newest decoded packet currently available.
+
+        It drains old buffered packets so the PC side follows the latest DIN/DOUT state.
+        Useful when camera/image saving is slower than ESP32 50Hz output.
+        """
+        self._require_open()
+
+        latest = self.read_packet()
+        drained = 0
+
+        while drained < max_drain:
+            # Pull all currently available bytes from OS serial buffer.
+            waiting = self.ser.in_waiting
+            if waiting <= 0 and len(self.buffer) < PACKET_SIZE:
+                break
+
+            if waiting > 0:
+                chunk = self.ser.read(waiting)
+                if chunk:
+                    self.buffer.extend(chunk)
+
+            packet = self._try_pop_packet()
+
+            if packet is None:
+                break
+
+            latest = decode_packet(packet)
+            drained += 1
+
+        return latest, drained
+
+def flatten_packet(data, t_s, freq_hz):
+    return {
+        "t_s": t_s,
+        "acc_x_g": data["acc_g"][0],
+        "acc_y_g": data["acc_g"][1],
+        "acc_z_g": data["acc_g"][2],
+        "gyro_x_dps": data["gyro_dps"][0],
+        "gyro_y_dps": data["gyro_dps"][1],
+        "gyro_z_dps": data["gyro_dps"][2],
+        "angle_x_deg": data["angle_deg"][0],
+        "angle_y_deg": data["angle_deg"][1],
+        "angle_z_deg": data["angle_deg"][2],
+        "temp_c": data["temp_c"],
+        "freq_hz": freq_hz,
+        "din0": data["din"][0],
+        "din1": data["din"][1],
+        "din2": data["din"][2],
+        "din3": data["din"][3],
+        "dout0": data["dout"][0],
+        "dout1": data["dout"][1],
+    }
+