Запись данных из файла в файл

cat mr.bin | tee /tmp/rs485 | hexdump -C

00000000: 001122

00 11 22

#!/usr/bin/python3

import struct

POLYNOMIAL = 0xA001

def crc(packet):
    crc = 0xffff
    #do{
    for ch in packet:
    #   /* Exclusive-OR the byte with the CRC */
    #   crc ^= (unsigned int)*char_ptr;
        crc = crc ^ (ch & 0x00ff)
    #   /* Loop through all 8 data bits */
    #   bit_count = 0;
    #   do{
        for i in range(8):
    #       /* If the LSB is 1, shift the CRC and XOR the polynomial mask with the CRC */
    #       if(crc & 0x0001){
            if (crc & 1) != 0:
    #           crc >>= 1;
                crc = crc >> 1
    #           crc ^= POLYNOMIAL;
                crc = crc ^ POLYNOMIAL
    #       }
    #       /* If the LSB is 0, shift the CRC only */
    #       else {
            else:
    #          crc >>= 1;
                crc = crc >> 1
    #      }
    #   } while(bit_count++ < 7);
    #} while(char_ptr++ < end_of_packet);
    crcl = (crc >> 0) & 0xff
    crch = (crc >> 8) & 0xff
    return packet + bytes([crcl, crch])

def fc_01(adr, start, quantity):
    return crc(struct.pack('>BBHH', adr, 1, start, quantity))

packet = fc_01(5, 0x0100, 8)

print('send: %s' % ['%02x' % x for x in packet])

rs = open('/tmp/rs485', 'wb')
rs.write(packet)
rs.flush()
rs.close()

#!/bin/bash

rm -f rs485 a.out

mkfifo rs485

gcc -x c - <<EOF
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>

#define MAX_BUF 10

int main()
{
    int fd;
    char * myfifo = "rs485";
    char buf[MAX_BUF];

    /* open, read, and display the message from the FIFO */
    fd = open(myfifo, O_RDONLY);
    read(fd, buf, MAX_BUF);
    printf("Received: %s\n", buf);
    close(fd);

    return 0;
}
EOF

./a.out &

python3 -- <<EOF
import struct

POLYNOMIAL = 0xA001

def crc(packet):
    crc = 0xffff
    for ch in packet:
        crc = crc ^ (ch & 0x00ff)
        for i in range(8):
            if (crc & 1) != 0:
                crc = crc >> 1
                crc = crc ^ POLYNOMIAL
            else:
                crc = crc >> 1
    crcl = (crc >> 0) & 0xff
    crch = (crc >> 8) & 0xff
    return packet + bytes([crcl, crch])

def fc_01(adr, start, quantity):
    return crc(struct.pack('>BBHH', adr, 1, start, quantity))

packet = fc_01(5, 0x0100, 8)

print('send: %s' % ['%02x' % x for x in packet])

rs = open('rs485', 'wb')
rs.write(packet)
rs.flush()
rs.close()
EOF

rs = open('rs485', 'wb')

rs = open('mr.bin', 'wb')

cat mr.bin | tee rs485 | hexdump -C