Static DFU Serial Number on STM32F723xx

[jwj]

There have been previous posts about determining how the DFU serial number is formed from the 96-bit Unique ID.  However, when using the ROM bootloader for the STM32F723xx MCU I don't see unique serial numbers at all.  I am always seeing the same DFU serial number in the iSerial string of the USB descriptor set to "STM32FxSTM32" no matter which device I query.  

I haven't found any mention of a setting that I need to configure in order to enable unique serial numbers for DFU, but I was hoping that someone in the community might have a suggestion.  Or at least be able to confirm that it is expected behavior for the DFU serial number to always be "STM32FxSTM32" for all of my STM32F723xx MCUs.

Thanks for the help!

[TDK]

The USB DFU bootloader is in ROM so there is nothing that can be configured. You get what you get.

I don't see anything in the documentation which suggests the SN is unique, or tied to the UID. That may be the observed behavior, but I wouldn't treat it as a guarantee.

USB DFU protocol used in the STM32 bootloader - Application note

 

On STM32F4x and STM32H7x boards, the "SN" field as reported by STM32CubeProgrammer appears to be random. Don't have an F7x board to test.

 

[jwj]

@TDK , thanks for the reply.  I also did not see anything about the SN used in DFU in the documentation (thanks for confirming that).  As illustrated in your screen captures, you are seeing some sort of hash based on the 96-bit unique ID (I'm basing this on previous posts and some Googling that have shown how reverse engineer this hash).  If you have two of the same MCU, I suspect that you will see different serial numbers.

DFU USB serial number and runtime STCubeMX generated USB serial number differ. 
STM32F765: Different USB serial number in DFU and APP modes
DFU Serial Number

For the all of the STM32F723xx boards that I have (STM32F723E-DISCO and all of our boards that we've built with the STM32F723xx MCU), the "SN" field as reported by STM32CubeProgrammer always has the same value of "STM32FxSTM32".  This seems like a departure from the behavior of other MCU families, so I am just trying to determine if this is user error on my part (e.g., there's a special Option Bytes setting that isn't documented that I need to turn on to get something other than "STM32FxSTM32") or if this is just how this part works.

 

If anyone has an STM323F723xx board and can verify, I'd appreciate that.
If anyone at ST can confirm that this is expected behavior for this part I would also appreciate that.

Thanks!