DFU Serial Number

[Rob.Riggs]

I am looking at the code here that has the algorithm for producing the device serial number reported when the MCU is in USB DFU mode.

https://github.com/libopencm3/libopencm3/blob/master/lib/stm32/desig.c

The document they reference there, https://my.st.com/52d187b7, is now a dead link. Does anyone have the name of the document and its current location?

[Tesla DeLorean · Accepted solution]

It's is likely are very old forum reference. Perhaps @brk​ or @Amel NASRI​ can dig it out

The interference here is this is a 6-byte contraction used by the System Loader. I would suppose you could quickly verify this by pulling the 96-bit unique ID for a unit and contrasting that with the reported serial number.

UM0424 doesn't really cover this

https://www.st.com/content/ccc/resource/technical/document/user_manual/01/c6/32/df/79/ad/48/32/CD00158241.pdf/files/CD00158241.pdf/jcr:content/translations/en.CD00158241.pdf

And the Get_SerialNum() here has an 8-byte implementation

https://github.com/fthorey/swiftler-bones/blob/master/stm32/STM32_USB-FS-Device_Lib_V3.3.0/Project/Device_Firmware_Upgrade/src/hw_config.c

[Brian Kling]

The link is not a community link, perhaps @Amel NASRI​ can assist.

[Amel NASRI]

Yes this seems to be an old link in the platform used before migrating to Jive.

[Tesla DeLorean]

Unfortunately the "search" functionality now is less than stellar.

Does the System Loader do some contraction of the Unique ID?

[Rob.Riggs]

The code I referenced does indeed match the serial number of the DFU serial number. I was just hoping to have an official reference to the algorithm I could point to. Finding dead links to a major developer resource like st.com is rather disappointing.

[Tesla DeLorean]

ST has gone through at least 4 forum softwares, a lot of content has been damaged or lost.

Unfortunately the cite in the code you provided lacks any title information so it's have to cross-reference via other means.

I don't recall the post or the functionality described in DFU related docs.

	uint8_t *id = (uint8_t *)DESIG_UNIQUE_ID_BASE;
 
	uint8_t serial[6];
	serial[0] = id[11];
	serial[1] = id[10] + id[2];
	serial[2] = id[9];
	serial[3] = id[8] + id[0];
	serial[4] = id[7];
	serial[5] = id[6];

[Tesla DeLorean]

https://www.st.com/content/ccc/resource/technical/document/user_manual/01/c6/32/df/79/ad/48/32/CD00158241.pdf/files/CD00158241.pdf/jcr:content/translations/en.CD00158241.pdf

"In all available demos in the “STM32 USB-FS_Device developer kit�? there is an example implementing a unique serial number string descriptor based on the STM32 Device Unique ID register (12 digits)."

Here from V3.2.1 does not look consistent

/*******************************************************************************
* Function Name  : Get_SerialNum.
* Description    : Create the serial number string descriptor.
* Input          : None.
* Output         : None.
* Return         : None.
*******************************************************************************/
void Get_SerialNum(void)
{
  uint32_t Device_Serial0, Device_Serial1, Device_Serial2;
 
  Device_Serial0 = *(__IO uint32_t*)(0x1FFFF7E8);
  Device_Serial1 = *(__IO uint32_t*)(0x1FFFF7EC);
  Device_Serial2 = *(__IO uint32_t*)(0x1FFFF7F0);
 
  Device_Serial0 += Device_Serial2;
 
  if (Device_Serial0 != 0)
  {
    IntToUnicode (Device_Serial0, &DFU_StringSerial[2] , 8);
    IntToUnicode (Device_Serial1, &DFU_StringSerial[18], 4);
  }
}
 
/*******************************************************************************
* Function Name  : HexToChar.
* Description    : Convert Hex 32Bits value into char.
* Input          : None.
* Output         : None.
* Return         : None.
*******************************************************************************/
static void IntToUnicode (uint32_t value , uint8_t *pbuf , uint8_t len)
{
  uint8_t idx = 0;
 
  for( idx = 0 ; idx < len ; idx ++)
  {
    if( ((value >> 28)) < 0xA )
    {
      pbuf[ 2* idx] = (value >> 28) + '0';
    }
    else
    {
      pbuf[2* idx] = (value >> 28) + 'A' - 10;
    }
 
    value = value << 4;
 
    pbuf[ 2* idx + 1] = 0;
  }
} 

STM32 DFU Serial Unique

[waclawek.jan]

I doubt this is unique enough.

JW

[Rob.Riggs]

Maybe ST would like to comment on why this implementation was chosen and what sort of uniqueness guarantees it does make.