Posted by Just1M on 2019-04-24 11:34

I know that the ST-LINK Utility from ST is capable of editing the Option Bytes.

In my experience System Workbench is not capable of doing so. Plus System Workbench is not the tool I planned to use in production. Two good reasons to find an other way to flash the Option Bytes: embed them into the binary file.

Here is an extract of my source code:

// 0x 1FFF F800 -> Option Byte 1 (nUSER, USER, nRDP, RDP)
const uint32_t optionbytes1 attribute(( section(“.optionbytes1”) )) = 0x20DF55AA;
// 0x 1FFF F804 -> Option Byte 2 (nData1, Data1, nData0, Data0)
const uint32_t optionbytes2 attribute(( section(“.optionbytes2”) )) = 0x00FF00FF;
// 0x 1FFF F808 -> Option Byte 3 (nWRP1, WRP1, nWRP0, WRP0)
const uint32_t optionbytes3 attribute(( section(“.optionbytes3”) )) = 0x00FF00FF;
// 0x 1FFF F80C -> Option Byte 4 (nWRP3, WRP3, nWRP2, WRP2)
const uint32_t optionbytes4 attribute(( section(“.optionbytes4”) )) = 0x00FF00FF;

Here is an extract of my Linker script:

MEMORY
{
...
FUSES (r) : ORIGIN = 0x1FFFF800, LENGTH = 16 /* Option Bytes (configuration fuses) */
...
}

SECTIONS
{
...
.fuses :
{
. = ALIGN(4);
KEEP(*(.optionbytes1))
KEEP(*(.optionbytes2))
KEEP(*(.optionbytes3))
KEEP(*(.optionbytes4))
. = ALIGN(4);
} >FUSES
...
}

In the end I obtain a binary file that embeds a section relative to the Option Bytes.
Here is an extract of my *.hex file:

:020000041FFFDC
:10F80000AA55DF20FF00FF0000FF00FFFF00FF0000

Doing like that allows you to flash your Option Bytes from System Workbench!