fix(pm3py): disable CRC for USB (matching C client), fix CRC byte order for FPC UART

pm3py/transport.py

@@ -14,15 +14,20 @@ from .protocol import (
 )
 
 
-def encode_ng_frame(cmd: int, payload: bytes = b"", use_crc: bool = True) -> bytes:
-    """Encode an NG command frame."""
+def _crc_to_wire(crc: int) -> int:
+    """Byte-swap CRC to match PM3 wire format: (low << 8) | high."""
+    return ((crc & 0xFF) << 8) | ((crc >> 8) & 0xFF)
+
+
+def encode_ng_frame(cmd: int, payload: bytes = b"", use_crc: bool = False) -> bytes:
+    """Encode an NG command frame. use_crc=False for USB (default), True for FPC UART."""
     if len(payload) > PM3_CMD_DATA_SIZE:
         raise ValueError(f"Payload too large: {len(payload)} > {PM3_CMD_DATA_SIZE}")
     length_ng = len(payload) | 0x8000  # set ng bit
     preamble = struct.pack("<IHH", CMD_PREAMBLE_MAGIC, length_ng, cmd)
     body = preamble + payload
     if use_crc:
-        crc = crc16_a(body)
+        crc = _crc_to_wire(crc16_a(body))
     else:
         crc = CMD_POSTAMBLE_NOCRC
     postamble = struct.pack("<H", crc)
@@ -30,8 +35,8 @@ def encode_ng_frame(cmd: int, payload: bytes = b"", use_crc: bool = True) -> byt
 
 
 def encode_mix_frame(cmd: int, arg0: int = 0, arg1: int = 0, arg2: int = 0,
-                     payload: bytes = b"", use_crc: bool = True) -> bytes:
-    """Encode a MIX command frame (NG wire format with OLD-style args)."""
+                     payload: bytes = b"", use_crc: bool = False) -> bytes:
+    """Encode a MIX command frame (NG wire format with OLD-style args). use_crc=False for USB."""
     args = struct.pack("<QQQ", arg0, arg1, arg2)
     full_payload = args + payload
     if len(full_payload) > PM3_CMD_DATA_SIZE:
@@ -40,7 +45,7 @@ def encode_mix_frame(cmd: int, arg0: int = 0, arg1: int = 0, arg2: int = 0,
     preamble = struct.pack("<IHH", CMD_PREAMBLE_MAGIC, length_ng, cmd)
     body = preamble + full_payload
     if use_crc:
-        crc = crc16_a(body)
+        crc = _crc_to_wire(crc16_a(body))
     else:
         crc = CMD_POSTAMBLE_NOCRC
     postamble = struct.pack("<H", crc)
@@ -67,7 +72,7 @@ def decode_response_frame(data: bytes) -> dict:
 
     # Verify CRC unless it's the no-CRC magic
     if crc_received != RESP_POSTAMBLE_NOCRC:
-        crc_expected = crc16_a(data[:RESP_PREAMBLE_SIZE + payload_len])
+        crc_expected = _crc_to_wire(crc16_a(data[:RESP_PREAMBLE_SIZE + payload_len]))
         if crc_received != crc_expected:
             raise ValueError(f"CRC mismatch: got 0x{crc_received:04X}, expected 0x{crc_expected:04X}")
 
@@ -129,8 +134,20 @@ class PM3Transport:
     async def connect(self) -> None:
         import serial_asyncio
         self._reader, self._writer = await serial_asyncio.open_serial_connection(
-            url=self.port, baudrate=self.baudrate,
+            url=self.port,
+            baudrate=self.baudrate,
+            bytesize=8,
+            parity="N",
+            stopbits=1,
+            xonxoff=False,
+            rtscts=False,
+            dsrdtr=False,
         )
+        # Match C client: no flow control, flush stale data
+        transport = self._writer.transport
+        if hasattr(transport, 'serial'):
+            transport.serial.reset_input_buffer()
+            transport.serial.reset_output_buffer()
 
     async def disconnect(self) -> None:
         if self._writer: