calc_crc.py

#!/usr/bin/env python3

import sys
import math


CRC_16_MODBUS = [
    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,
]

PAGESIZE = 128


def crc16modbus_byte(crc: int, byte: int) -> int:
    return (crc >> 8) ^ CRC_16_MODBUS[(crc ^ byte) & 0xff]


def calc_crc(in_filename: str, out_filename: str, crc_addr: int) -> None:
    with open(in_filename, 'r') as infile, open(out_filename, 'w') as outfile:
        nextaddr = 0
        crc = 0
        skip = False
        offset = 0

        for line in infile:
            assert line.startswith(':')
            bytes_count = int(line[1:3], base=16)
            addr = int(line[3:7], base=16)
            type_ = int(line[7:9])

            if type_ == 2:
                offset = int(line[9:13], base=16)*16

            if type_ == 0 and offset+addr == crc_addr:
                while nextaddr % PAGESIZE > 0:
                    crc = crc16modbus_byte(crc, 0xFF)
                    nextaddr += 1

                pages = math.ceil(nextaddr//PAGESIZE)
                print(f'Total {nextaddr} bytes = {pages} pages'
                      f', CRC is {hex(crc)}.')
                data = [
                    0x03,
                    (crc_addr >> 8) & 0xFF,
                    crc_addr & 0xFF,
                    0,
                    pages,
                    crc & 0xFF,
                    (crc >> 8) & 0xFF,
                ]

                sum_ = 0
                for d in data:
                    sum_ += d
                data.append(int(bin(-sum_ & 0xFF), base=2))

                outfile.write(
                    ':'+''.join(hex(d)[2:].zfill(2).upper() for d in data)+'\n'
                )
                skip = True
                continue

            if not skip and type_ == 0:
                assert offset == 0, 'Offset of code not yet supported'
                assert nextaddr == addr, line
                nextaddr += bytes_count
                data = line[9:-3]
                for i in range(0, len(data), 2):
                    databyte = int(data[i:i+2], base=16)
                    crc = crc16modbus_byte(crc, databyte)

            outfile.write(line)


if __name__ == '__main__':
    if len(sys.argv) < 4:
        sys.stderr.write('Usage: calc_crc.py ihexfile ohexfile crc-address-hex\n')
        sys.exit(1)

    in_filename, out_filename, crc_addr = sys.argv[1], sys.argv[2], int(sys.argv[3], base=16)
    calc_crc(in_filename, out_filename, crc_addr)