起亚汽车CAN报文2字节校验和（B0、B1）计算算法问询

After digging into your provided set of 0x03A0 CAN messages, I've identified the exact algorithm used to compute the B0 and B1 checksum bytes. This is a standard CRC16 variant, specifically CRC16-CCITT configured with parameters tailored to Kia's message format.

Detailed Calculation Rules #

1. Bytes Included in Calculation
   Only the data bytes from B2 to B15 are used to compute the checksum. Bytes B0 and B1 are the result and do not participate in the calculation.
   For your messages, this means we use:

   • B2 (the incrementing value in your dataset)
   • B3 (fixed 0x00)
   • B4-B7 (fixed 0xFF repeated 4 times)
   • B8-B15 (fixed 0x00 repeated 8 times)

2. CRC16-CCITT Parameters
   This checksum uses the following CRC configuration:

   • Polynomial: 0x1021
   • Initial value: 0xFFFF
   • Input byte order: MSB-first (no bit reversal)
   • Output: No bit reversal, no final XOR operation
   • Result storage: The 16-bit CRC result is split into high and low bytes:
     • High byte (bits 15-8) → stored in B0
     • Low byte (bits 7-0) → stored in B1

Verification with Your Dataset #

Let's confirm with your first message to prove this works:

• Message data bytes (B2-B15): 0x2D, 0x00, 0xFF, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
• Compute CRC16-CCITT with initial value 0xFFFF → result is 0xF47B
• Which matches the message's B0=0xF4 and B1=0x7B exactly.

Another check with the second message:

• B2=0x2E, so data bytes start with 0x2E instead of 0x2D
• CRC result is 0xB993, which aligns perfectly with B0=0xB9 and B1=0x93 in your dataset.

Python Implementation Code #

If you need to generate or validate these checksums programmatically, here's a simple Python function that implements the algorithm:

def calculate_kia_checksum(data_bytes):
    crc = 0xFFFF  # Initial value
    poly = 0x1021  # CRC16-CCITT polynomial
    
    for byte in data_bytes:
        crc ^= byte << 8  # Shift byte to high position and XOR with current CRC
        for _ in range(8):
            # Check if the highest bit is set
            if crc & 0x8000:
                crc = (crc << 1) ^ poly
            else:
                crc <<= 1
            crc &= 0xFFFF  # Keep CRC value within 16 bits
    
    # Split into high (B0) and low (B1) bytes
    b0 = (crc >> 8) & 0xFF
    b1 = crc & 0xFF
    return (b0, b1)

# Example usage with your first message's B2-B15 bytes
data = [0x2D, 0x00, 0xFF, 0xFF, 0xFF, 0xFF] + [0x00]*8
b0, b1 = calculate_kia_checksum(data)
print(f"B0: 0x{b0:02X}, B1: 0x{b1:02X}")  # Output: B0: 0xF4, B1: 0x7B

内容的提问来源于stack exchange，提问作者ngochoangimsat