ODrive serial numbers

Riewert · December 18, 2020, 12:44pm

I just happened to notice that my ODrives have very similar serial number endings. I’m guessing there is some kind of date encoded in the numbers, I’m curious what it is?

I have:
205C39874D4D
2064399A4D4D
386837583437
205839894D4D
207435A2524B
205E3590524B

madcowswe · December 21, 2020, 3:30am

The serial number is computed with this code:

github.com

madcowswe/ODrive/blob/320be744136fe096a4900093f0445e3838751696/Firmware/MotorControl/main.cpp#L637-L644


// This procedure of building a USB serial number should be identical
// to the way the STM's built-in USB bootloader does it. This means
// that the device will have the same serial number in normal and DFU mode.
uint32_t uuid0 = *(uint32_t *)(UID_BASE + 0);
uint32_t uuid1 = *(uint32_t *)(UID_BASE + 4);
uint32_t uuid2 = *(uint32_t *)(UID_BASE + 8);
uint32_t uuid_mixed_part = uuid0 + uuid2;
serial_number = ((uint64_t)uuid_mixed_part << 16) | (uint64_t)(uuid1 >> 16);

Using the Unique ID that are present in all STM32’s. As for how those are assigned, it seems to be components made of:

X and Y coordinates on the wafer expressed in sign-magnitude format
lot number
wafer number

See:

Tracing through the calculation, it would seem that the identical lower 16 bits you see is because they came from the same wafer.

Riewert · December 21, 2020, 10:57am

Cool, nice to know and great explanation. I always wondered how that worked.