Updating firmware through USB DFU with Readout Protection level 1

[j_filipe]

Greetings, 
I'm making a project, using a B-U585I-IOT02A board in which I made a Java program that can flash a firmware (using the USB DFU protocol) and also set Readout Protection to Level 1 through the Option Bytes. The program can flash the firmware and set RDP level 1 successfully, but I wanted to be able to flash a firmware, using the USB DFU while having the RDP set to level 1 and I can't. Every time I set the RDP level 1, I can't upgrade using USB DFU, I need to use the STLINK, go to the STM32CubeProgrammer and set the Option Bytes back to level 0, which will mass erase the flash. 
I know I can't do all this with the STM32CubeProgrammer, but I want to be able to do it with my program (for personal reasons).
So the question is, how can I upgrade the firmware using USB DFU, with RDP set to level 1? 

Thank you! 

[STOne-32]

Dear @j_filipe ,

Can you try the scenario shown here  Introduction to Arm® TrustZone® features on STM32L5, STM32U5, and STM32U3 MCUs - Application note  Page 22 , figure 11

If RDP is set to level 1 and the TZEN regression cannot be done using the STM32CubeProgrammer graphical
interface, the STM32CubeProgrammer CLI (command line instructions) must be used, applying the following
TZEN regression command:
> STM32_Programmer_CLI.exe -c port=USB1 -tzenreg

Hope it helps.

STOne-32.

[j_filipe · Accepted solution]

Yeah, I'm not actually using STM32CubeProgrammer to do it. I made an implementation of DFU protocol in java to do that. But I already solved the issue, I needed to send a Read Unprotect (0x92) command to do it. Already did it. Thanks anyway!