How to protect reading flash of stm32f10x - stm32

Question

I am working on a project using STM32F103 and I have finished development of the firmware. I use ST-Link Utility for downloading stuff to the microcontroller. When I activate read out protection on my chip, it stops working. And I need to protect my firmware. What is the problem?

Answer 1

Just a bit more info to the accepted answer:
From ST32F10XXX docs, section "2.4.1 Read protection":
The read protection is activated by setting the RDP option byte and
then, by applying a system reset to reload the new RDP option byte.
Note: If the read protection is set while the debugger is still
connected through JTAG/SWD, apply a POR (power-on reset) instead of a
system reset (without debugger connection).
Once the protection byte
has been programmed:
Main Flash memory read access is not allowed
except for the user code (when booting from main Flash memory itself
with the debug mode not active).
Pages 0-3 (for low- and
medium-density devices), or pages 0-1 (for high-density and
connectivity line devices) are automatically write-protected. The rest
of the memory can be programmed by the code executed from the main
Flash memory (for IAP, constant storage, etc.), but it is protected
against write/erase (but not against mass erase) in debug mode or when
booting from the embedded SRAM.
All features linked to loading code into and executing code from the embedded SRAM
are still active (JTAG/SWD and boot from embedded SRAM) and this can be used to
disable the read protection. When the read protection option byte is altered to a
memory-unprotect value, a mass erase is performed.
When booting from the embedded SRAM, Flash memory accesses through the code
and through data read using DMA1 and DMA2 are not allowed.
Flash memory access through data read using JTAG, SWV (serial wire viewer), SWD
(serial wire debug), ETM and boundary scan are not allowed
Unprotection
To disable the read protection from the embedded SRAM:
Erase the entire option byte area. As a result, the read protection code (RDP) will be
0xFF. At this stage the read protection is still enabled.
Program the correct RDP code 0x00A5 to unprotect the memory. This operation first
forces a Mass Erase of the main Flash memory.
Reset the device (POR Reset) to reload the option bytes (and the new RDP code) and,
to disable the read protection.
Note: The read protection can be disabled using the boot loader (in this case only a System Reset
is necessary to reload the option bytes). For more details refer to AN2606.
There's also a write protection on the chip, see the doc.
ADDED: STM32 readout protection has problems: https://blog.zapb.de/stm32f1-exceptional-failure/ so be aware.

Answer 2

You have to unlock the flash first. There should be a call in the STM32 StdPeriph library. My code looks something like this:
/* Read protect the flash. NEVER EVER set this to level 2. You can't
* write to the chip ever again after that. */
FLASH_OB_Unlock();
FLASH_OB_RDPConfig( OB_RDP_Level_1 );
if (FLASH_OB_Launch() != FLASH_COMPLETE)
{
err_printf("Error enabling RDP\n");
}
FLASH_OB_Lock();