我也跟风造轮子,python用的modbus_crc16查表法

gaolf_2012

虽然python有modbus_tk模块,可还是想自己实现一个,先从crc入手
CRC16Table = (
    0x0000, 0xC0C1, 0xC181, 0x0140, 0xC301, 0x03C0, 0x0280, 0xC241,
    0xC601, 0x06C0, 0x0780, 0xC741, 0x0500, 0xC5C1, 0xC481, 0x0440,
    0xCC01, 0x0CC0, 0x0D80, 0xCD41, 0x0F00, 0xCFC1, 0xCE81, 0x0E40,
    0x0A00, 0xCAC1, 0xCB81, 0x0B40, 0xC901, 0x09C0, 0x0880, 0xC841,
    0xD801, 0x18C0, 0x1980, 0xD941, 0x1B00, 0xDBC1, 0xDA81, 0x1A40,
    0x1E00, 0xDEC1, 0xDF81, 0x1F40, 0xDD01, 0x1DC0, 0x1C80, 0xDC41,
    0x1400, 0xD4C1, 0xD581, 0x1540, 0xD701, 0x17C0, 0x1680, 0xD641,
    0xD201, 0x12C0, 0x1380, 0xD341, 0x1100, 0xD1C1, 0xD081, 0x1040,
    0xF001, 0x30C0, 0x3180, 0xF141, 0x3300, 0xF3C1, 0xF281, 0x3240,
    0x3600, 0xF6C1, 0xF781, 0x3740, 0xF501, 0x35C0, 0x3480, 0xF441,
    0x3C00, 0xFCC1, 0xFD81, 0x3D40, 0xFF01, 0x3FC0, 0x3E80, 0xFE41,
    0xFA01, 0x3AC0, 0x3B80, 0xFB41, 0x3900, 0xF9C1, 0xF881, 0x3840,
    0x2800, 0xE8C1, 0xE981, 0x2940, 0xEB01, 0x2BC0, 0x2A80, 0xEA41,
    0xEE01, 0x2EC0, 0x2F80, 0xEF41, 0x2D00, 0xEDC1, 0xEC81, 0x2C40,
    0xE401, 0x24C0, 0x2580, 0xE541, 0x2700, 0xE7C1, 0xE681, 0x2640,
    0x2200, 0xE2C1, 0xE381, 0x2340, 0xE101, 0x21C0, 0x2080, 0xE041,
    0xA001, 0x60C0, 0x6180, 0xA141, 0x6300, 0xA3C1, 0xA281, 0x6240,
    0x6600, 0xA6C1, 0xA781, 0x6740, 0xA501, 0x65C0, 0x6480, 0xA441,
    0x6C00, 0xACC1, 0xAD81, 0x6D40, 0xAF01, 0x6FC0, 0x6E80, 0xAE41,
    0xAA01, 0x6AC0, 0x6B80, 0xAB41, 0x6900, 0xA9C1, 0xA881, 0x6840,
    0x7800, 0xB8C1, 0xB981, 0x7940, 0xBB01, 0x7BC0, 0x7A80, 0xBA41,
    0xBE01, 0x7EC0, 0x7F80, 0xBF41, 0x7D00, 0xBDC1, 0xBC81, 0x7C40,
    0xB401, 0x74C0, 0x7580, 0xB541, 0x7700, 0xB7C1, 0xB681, 0x7640,
    0x7200, 0xB2C1, 0xB381, 0x7340, 0xB101, 0x71C0, 0x7080, 0xB041,
    0x5000, 0x90C1, 0x9181, 0x5140, 0x9301, 0x53C0, 0x5280, 0x9241,
    0x9601, 0x56C0, 0x5780, 0x9741, 0x5500, 0x95C1, 0x9481, 0x5440,
    0x9C01, 0x5CC0, 0x5D80, 0x9D41, 0x5F00, 0x9FC1, 0x9E81, 0x5E40,
    0x5A00, 0x9AC1, 0x9B81, 0x5B40, 0x9901, 0x59C0, 0x5880, 0x9841,
    0x8801, 0x48C0, 0x4980, 0x8941, 0x4B00, 0x8BC1, 0x8A81, 0x4A40,
    0x4E00, 0x8EC1, 0x8F81, 0x4F40, 0x8D01, 0x4DC0, 0x4C80, 0x8C41,
    0x4400, 0x84C1, 0x8581, 0x4540, 0x8701, 0x47C0, 0x4680, 0x8641,
    0x8201, 0x42C0, 0x4380, 0x8341, 0x4100, 0x81C1, 0x8081, 0x4040
)

def g_crc16(data_buff, lens):
        crc = 0xffff
        index = 0

        for i in range(lens):
                index = ((crc & 0xff) ^ (data_buff[i] & 0xff))
                crc  = ((crc >> 8) & 0xff) ^ CRC16Table[index]
        return ((crc&0xff)<<8) + (crc>>8)

def gen_read_hold_reg(dev_id, start_addr, nums):
    cmd_buff = [0 for _ in range(8)]
    lens = 8
    cmd_buff[0] = dev_id
    cmd_buff[1] = 0x03
    cmd_buff[2] = start_addr >> 8
    cmd_buff[3] = start_addr & 0xff
    cmd_buff[4] = nums >> 8
    cmd_buff[5] = nums & 0xff
    #crc_data = crc16(cmd_buff,6)
    crc_data = g_crc16(cmd_buff,6)
    cmd_buff[6] = crc_data>>8
    cmd_buff[7] = crc_data & 0xff
    return cmd_buff

wgainn

python用起来真爽，我也贴个python计算 crc

1. invert8=lambda x:(((x) & 1) << 7 | \
   
2.             (((x) >> 1) & 1) << 6 | \
   
3.             (((x) >> 2) & 1) << 5 | \
   
4.             (((x) >> 3) & 1) << 4 | \
   
5.             (((x) >> 4) & 1) << 3 | \
   
6.             (((x) >> 5) & 1) << 2 | \
   
7.             (((x) >> 6) & 1) << 1 | \
   
8.             (((x) >> 7) & 1))
   
9. invert16= lambda x: (invert8(x & 0xff) << 8) | (invert8(x >> 8))
   
10. def calc_crc16(crc, databuf, dlen):
    
11.     tmp=0
    
12.     for i in range(dlen):
    
13.         tmp = databuf[i];
    
14.         tmp = invert8(tmp)
    
15.         crc ^= (tmp << 8)
    
16.         tmp = 0
    
17.         while tmp < 8:
    
18.             tmp+=1
    
19.             if(crc & 0x8000):
    
20.                 crc = (crc << 1) ^ 0x8005
    
21.             else:
    
22.                 crc <<= 1;
    
23.     crc = invert16(crc);
    
24.     bb=(crc>>8, crc & 0xff)
    
25.     return bb
    

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