Intel HEX (IHEX) format read/write library in C
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A small library for reading and writing the Intel HEX (or IHEX) format. The library is mainly intended for embedded systems and microcontrollers, such as Arduino, AVR, PIC, ARM, STM32, etc - hence the emphasis is on small size rather than features, generality, or error handling.

See the header file kk_ihex.h for documentation, or below for simple examples.

~ Kimmo Kulovesi, 2013-12-27


Basic usage for writing binary data as IHEX ASCII:

#include "kk_ihex_write.h"
struct ihex_state ihex;
ihex_write_at_address(&ihex, 0);
ihex_write_bytes(&ihex, my_data_bytes, my_data_size);

The function ihex_write_bytes may be called multiple times to pass any amount of data at a time.

The actual writing is done by a callback called ihex_flush_buffer, which must be implemented, e.g., as follows:

void ihex_flush_buffer(struct ihex_state *ihex, char *buffer, char *eptr) {
    *eptr = '\0';
    (void) fputs(buffer, stdout);

The length of the buffer can be obtained from eptr - buffer. The actual implementation may of course do with the IHEX data as it pleases, e.g., transmit it over a serial port.

For a complete example, see the included program bin2ihex.c.


Basic usage for reading ASCII IHEX into binary data:

#include "kk_ihex_read.h"
struct ihex_state ihex;
ihex_read_bytes(&ihex, my_ascii_bytes, my_ascii_length);

The function ihex_read_bytes may be called multiple times to pass any amount of data at a time.

The reading functions call the function ihex_data_read, which must be implemented by the caller to store the binary data, e.g., as follows:

ihex_bool_t ihex_data_read (struct ihex_state *ihex,
                            ihex_record_type_t type,
                            ihex_bool_t checksum_error) {
    if (type == IHEX_DATA_RECORD) {
        unsigned long address = (unsigned long) IHEX_LINEAR_ADDRESS(ihex);
        (void) fseek(outfile, address, SEEK_SET);
        (void) fwrite(ihex->data, ihex->length, 1, outfile);
    } else if (type == IHEX_END_OF_FILE_RECORD) {
        (void) fclose(outfile);
    return true;

Of course an actual implementation is free to do with the data as it chooses, e.g., burn it on an EEPROM instead of writing it to a file.

For an example complete with error handling, see the included program ihex2bin.c.

Example Programs

The included example programs, ihex2bin and bin2ihex, implement a very simple conversion between raw binary data and Intel HEX. Usage by example:

# Simple conversion from binary to IHEX:
bin2ihex <infile.bin >outfile.hex

# Add an offset to the output addresses (i.e., make the address
# of the first byte of the input other than zero):
bin2ihex -a 0x8000000 -i infile.bin -o outfile.hex

# Simple conversion from IHEX to binary:
ihex2bin <infile.hex >outfile.bin

# Manually specify the initial address written (i.e., subtract
# an offset from the input addresses):
ihex2bin -a 0x8000000 -i infile.hex -o outfile.bin

# Start output at the first data byte (i.e., make the address offset
# equal to the address of the first data byte read from input):
ihex2bin -A -i infile.hex -o outfile.bin

Both programs also accept the option -v to increase verbosity.

When using ihex2bin on Intel HEX files produced by compilers and such, it is a good idea to specify the command-line option -A to autodetect the address offset. Otherwise the program will simply fill any unused addresses, starting from 0, with zero bytes, which may total mega- or even gigabytes.