BMW DS2 Protocol Frame Structure (MS41, MS42, MS43)

Diagnostics, ECU flashing, and live telemetry across BMW generations operate through four standardized protocols:

┌──────────────────────────────────────────────────────────────────────────────────────────────────┐  
│                   DIAGNOSTIC PROTOCOL HIERARCHY & BANDWIDTH EVOLUTION                            │  
├──────────────────────────────────────────────────────────────────────────────────────────────────┤  
│                                                                                                  │  
│   1. BMW DS2 PROTOCOL (K-Line @ 9600 Baud / MS41, MS42, MS43):                                   │  
│      • Point-to-point serial communication over single ISO 9141 K-Line (OBD Pin 7).              │  
│      • Payload: Diagnostic request packets (Header + Length + Target ID + Command + XOR Checksum)│  
│      • Sample Rate Ceiling: Sluggish 4 Hz to 8 Hz polling rate.                                  │  
│                                                                                                  │  
│   2. KWP2000 DIAGNOSTICS (K-Line or CAN @ 10,400 to 125,000 Baud / MS45.0, EDC15, EDC16):       │  
│      • Keyword Protocol 2000 (ISO 14230). Defined in database by if_kwp6.a2l.                    │  
│      • Supports local identifier polling and flash routine downloading.                          │  
│                                                                                                  │  
│   3. CAN CALIBRATION PROTOCOL (CCP v2.1 @ 500 kbps / MS45.1, MSS54, MSD80):                      │  
│      • Master-Slave protocol running directly over PT-CAN bus. Defined by If_ccp4.a2l.           │  
│      • Synchronous Data Acquisition (DAQ) lists streaming internal RAM variables at 50 Hz!       │  
│                                                                                                  │  
│   4. UDS OVER CAN & DOIP (ISO 14229 & ISO 13400 / MEVD17, MG1, DME8):                           │  
│      • Unified Diagnostic Services over CAN (500 kbps) and Diagnostic over IP (100 Mbps Ethernet)│  
└──────────────────────────────────────────────────────────────────────────────────────────────────┘  

20.1 BMW DS2 Protocol Frame Structure (MS41, MS42, MS43)#

BMW DS2 communicates half-duplex at 9600 ext{ baud} (8 ext{ data bits}, 1 ext{ stop bit}, even or no parity) over the single OBD-II pin 7 K-Line: ext{Frame Structure: } [ ext{Target Address}] \quad [ ext{Length}] \quad [ ext{Command}] \quad [ ext{Data Payload}\dots] \quad [ ext{XOR Checksum}]

def build_ds2_packet(target_addr: int, cmd: int, payload: bytes = b"") -> bytes:  
  length = 3 + len(payload)  
  packet_body = bytes([target_addr, length, cmd]) + payload  
  checksum = 0  
  for byte in packet_body:  
    checksum ^= byte  
  return packet_body + bytes([checksum])

# Example: Read ECU Identification (Hardware/Software Number)  
packet_ident = build_ds2_packet(0x12, 0x00)  # b'    '  

20.2 CAN Calibration Protocol (CCP v2.1) High-Speed DAQ Streaming#

Cataloged in the DAMOS archives by If_ccp4.a2l, CCP v2.1 provides professional-grade calibration acquisition on MS45.1, MSS54, and MSD80: