Possible counterfeit STM32F405? Nearly identical MCU IDs on two Betaflight flight controllers

[BPrac.1]

Hi,

I have two identical flight controllers from BetaFPV:

https://betafpv.com/products/f405-4s-20a-toothpick-brushless-flight-controller-v5-blheli_s-icm42688?_pos=11&_sid=55080f3df&_ss=r

both using an STM32F405 MCU. I noticed that the unique device IDs (UIDs) on both are suspiciously similar. Here they are:

• 0025001e3133510c34383739

• 002300283133510c34383739

As you can see, the last 64 bits (3133510C34383739) are exactly the same on both chips. Only the first 32 bits differ slightly.

Since STM32 MCUs are supposed to have globally unique 96-bit identifiers, this seems strange. Could this be a sign that the chips are counterfeit or cloned? Or is it possible (though unlikely) that chips from the same production batch could share most of the UID?

Any insight from ST or community experts would be appreciated.

Thanks in advance!

I bought both from the same online store, a little more than a month apart.

[TDK]

Different chips on the same wafer will have the same UID except X and Y position, exactly as you've shown. Doesn't seem suspicious in the slightest to me. Probably a sign that the store you're buying from doesn't go through much inventory.

 

 

[CTapp.1]

Why do you think there is an issue when they are different but contain common sequences?

I've not got the data sheet for the F4 to hand, but the one for the G4 shows that the registers holding the device's electronic signature hold:

Bits 31:0 UID[31:0]: X and Y coordinates on the wafer
Bits 31:8 UID[63:40]: LOT_NUM[23:0] Lot number (ASCII encoded)
Bits 7:0 UID[39:32]: WAF_NUM[7:0] Wafer number (8-bit unsigned number)
Bits 31:0 UID[95:64]: LOT_NUM[55:24] Lot number (ASCII encoded)

From that, it would appear that common sequences for devices from the same batch would be likely.