Unique Serial ID - Hidden Serial Number
The datasheet of the Atmega328pb chip has a section 'Serial Number' how explain every chip have a unique device ID with 10 bytes.
The datasheet of the Atmega328p chip does not say anything about the serial number, but I tested using the same Z-pointer Address on the datasheet of the Atmega328pb.
Apparently, the chip Atmega328p have a hidden serial number with 9 bytes, and others AVR Microcontroller maybe too, like the table below.
| Z-pointer Address | Atmega328pb | Atmega328p |
|---|---|---|
| 0x000E | Byte 0 | Byte 0 |
| 0x000F | Byte 1 | Byte 1 |
| 0x0010 | Byte 2 | Byte 2 |
| 0x0011 | Byte 3 | Byte 3 |
| 0x0012 | Byte 4 | Byte 4 |
| 0x0013 | Byte 5 | Byte 5 |
| 0x0014 | Byte 6 | - |
| 0x0015 | Byte 7 | Byte 6 |
| 0x0016 | Byte 8 | Byte 7 |
| 0x0017 | Byte 9 | Byte 8 |
- Atmega328pb - 10 bytes
- Atmega328p - 9 bytes (Not Unique)
- Atmega2560 - 9 bytes (Not Unique)
- Attiny85 - 9 bytes (Not Unique)
The Atmega328p, Atmega2560, Attiny85 does not have a 'Serial Number' on the datasheet, this mean it's possible to have two microcontroller with the same UniqueId.
Atmel SAM3X8E is used in Arduino Due.
The Unique Identifier is located in the first 128 bits of the Flash memory mapping. So, at the address 0x400000-0x400003.
"Each device integrates its own 128-bit unique identifier. These bits are factory configured and cannot be changed by the user. The ERASE pin has no effect on the unique identifier." Datasheet Section 7.2.3.7
- Atmel SAM3X8E ARM Cortex-M3 - 16 bytes
Each device has a unique 128-bit serial number which is a concatenation of four 32-bit words contained at the following addresses:
| - | SAMD21 | SAMD51 |
|---|---|---|
| Word 0 | 0x0080A00C | 0x008061FC |
| Word 1 | 0x0080A040 | 0x00806010 |
| Word 2 | 0x0080A044 | 0x00806014 |
| Word 3 | 0x0080A048 | 0x00806018 |
The uniqueness of the serial number is guaranteed only when using all 128 bits.
- Atmel SAMD21 ARM Cortex-M0 (Arduino Zero / Arduino M0) - 16 bytes - Datasheet Section 9.3.3
- Atmel SAMD51 ARM Cortex-M4 (Adafruit Metro M4)- 16 bytes - Datasheet Section 9.6
STM32 32-bit Arm Cortex MCUs has a unique 96-bit serial number which is a concatenation of three 32-bit words, the address is different depending on the microcontroller.
The Arduino Core STM32 has the functions HAL_GetUIDw0(), HAL_GetUIDw1() and HAL_GetUIDw2() for 96-bit UID.
- STM32F103C8 (BluePill Board) - 12 bytes
- STM32L073RZ (Nucleo L073RZ) - 12 bytes
ESP microcontroller has basically two versions, ESP8266 and ESP32, each one has a specific function to request the chip id.
- ESP8266 - ESP.getChipId() - 4 bytes
- ESP32 - ESP.getEfuseMac() - 6 bytes
| UniqueID | ESP8266 | ESP32 |
|---|---|---|
| Byte 0 | Byte 0 | Byte 5 |
| Byte 1 | Byte 1 | Byte 4 |
| Byte 2 | Byte 2 | Byte 3 |
| Byte 3 | Byte 3 | Byte 2 |
| Byte 4 | - | Byte 1 |
| Byte 5 | - | Byte 0 |
To make the variable UniqueID8 to work probably the library uses the default bytes to 0x00.
| UniqueID8 | ESP8266 | ESP32 |
|---|---|---|
| Byte 0 | 0x00 | 0x00 |
| Byte 1 | 0x00 | 0x00 |
| Byte 2 | 0x00 | Byte 5 |
| Byte 3 | 0x00 | Byte 4 |
| Byte 4 | Byte 0 | Byte 3 |
| Byte 5 | Byte 1 | Byte 2 |
| Byte 6 | Byte 2 | Byte 1 |
| Byte 7 | Byte 3 | Byte 0 |
- ESP8266 - 4 bytes
- ESP32 - 6 bytes
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