Unique ID per device

Question

I need a way to differentiate between multiple ESPapers.

Is there a source for a unique (or almost unique) identification between several boards? Is there maybe a serial number I can read? If that does not exist at all, is there a way to save a file to the device that stays around until the firmware is reprogrammed?

Further reading: https://arduino.stackexchange.com/questions/279/how-can-i-get-a-unique-id-for-all-my-arduino-boards

Answer 1

There's ESP.getChipId() which may be sufficient for your needs.

Serial.printf(" ESP8266 Chip id = %08X\n", ESP.getChipId());

By default, ESP sets its MAC address as a concatenation of 3 fixed bytes and 3 unique bytes burned into chip (which are read by getChipId function).

Comments

Awesome, thank you! Do you happen to know how unique this is? Could there be collisions?

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The first 24 bits (3-bytes) of the MAC are the identifier number of the manufacturer (e.g. Espressif) and the second group of 3-bytes (24 bits) is usually a serial number assigned by the manufacturer. So assume they always use the same manufacturers MAC prefix then you have a 1 in 2^24 chance of a part number collision, so that's a 16,777,216 to 1 chance of a collision and I doubt they have sold >16M parts yet, but maybe they have! even so the chance of you purchasing the same 3-byte serial must be so low as to be approaching zero.

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I know this is an older post but the 3-byte manufacturer that is used is not just one. I have many different combinations coming from my MAC addresses. Here are some samples:
68:C6:3A:xx:xx:xx
2C:3A:E8:xx:xx:xx
BC:DD:C2:xx:xx:xx

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That's correct. If you search https://wintelguy.com for 'Espressif' you get a list of (currently) 26 vendor numbers.