How to regress from RDP level 2 to RDP level 0 on the STM32U5 series
Summary
This article allows the process to regress from RDP 2 to RDP 0 on the STM32U5 series.
This example uses the STM32U5 Nucleo board with STM32U5A5ZJT6Q and STM32CubeProgrammer V2.13.
Note:
To regress from RDP2 to RDP0, you must be sure that your password has been defined in OEM2KEY. Otherwise, case regression is not possible.
1. How to define an OEM password
To define an OEM2 password, you must do the following:
1.Check if your sample is on RDP level 0 (no protection).
2. In the "secure programming" menu, define your password.
3. Click on "set password" and after on "apply lock RDP2."
At this point, you are sure that the OEM2Key is correctly defined.
2. How to take the RDP from level 0 to level 2
1. In the "read out protection" menu, select the value “CC" then click on apply.
After clicking on "ok" you will lose your connection with STLINK. This is normal behavior.
3. How to regress from RDP level 2 to level 0
Go back to the "secure programming" menu:
1. Click on "Unlock RDP2" and after on "Apply unlock RDP2."
You receive an error message but in your log window, you can read "Unlock RDP2 password successfully done."
2. After clicking on "ok" reconnect your card with STLINK, then check the device authentication ID by clicking on "Read."
3. Disable the RDP regression with a password.
4. Go back to the "Read Out Protection" menu and check the value of the RDP.
5. Change the RDP value to “AA” then click on apply.
You have correctly downgraded the RDP from level 2 to level 0.