# <avr/signature.h>: Signature Support

Introduction
The <avr/signature.h> header file allows the user to automatically and easily include the device's signature data in a special section of the final linked ELF file.

This value can then be used by programming software to compare the on-device signature with the signature recorded in the ELF file to look for a match before programming the device.

API Usage Example
Usage is very simple; just include the header file:
    #include <avr/signature.h>


This will declare a constant unsigned char array and it is initialized with the three signature bytes, MSB first, that are defined in the device I/O header file. This array is then placed in the .signature section in the resulting linked ELF file.

The three signature bytes that are used to initialize the array are these defined macros in the device I/O header file, from MSB to LSB: SIGNATURE_2, SIGNATURE_1, SIGNATURE_0.

This header file should only be included once in an application.