In some cases it is important to programmatically detect the micro-controller type, e.g., is it an ATmega328p or an ATmega2560 ? For example, when dealing with USART communication, we need to know the MCU type, because different MCUs have different number of USART ports and some of them even requires different settings for USART communication. While currently it is not possible to programmatically read the Arduino type (e.g., is it an Arduino UNO or a MEGA2560 ?), we can still detect the used MCU type.

Every ATmega MCU (and not only) has a signature code. This is not unique for every single chip, but it is unique for every MCU type. The AVR programming environment, provides three constants, SIGNATURE_0, SIGNATURE_1, and SIGNATURE_2 representing the three bytes of the signature code. Therefore, detecting the MCU type is as simple as reading these three constants and compare their values with the known ones for the chip type(s). The following Arduino sketch detects if we use an Atmega328P or an ATmega2560 MCU and uses the serial console to show this info:

char *mcuType;

void setup() {
  // enable serial communication on USART0 port
  Serial.begin( 115200);
  // is this an Atmel chip ?
  if ( SIGNATURE_0 == 0x1E || SIGNATURE_0 == 0x00) {
    if ( SIGNATURE_1 == 0x95 && SIGNATURE_2 == 0x0F) {
      mcuType = "ATmega328p";
    } else if ( SIGNATURE_1 == 0x98 && SIGNATURE_2 == 0x01) {
      mcuType = "ATmega2560";
    } else {
      mcuType = "Unknown Atmel"; 
    }
  } else {
    mcuType = "Unknown";
  }
}

void loop() { 
  Serial.print( "Your MCU type is: ");
  Serial.println( mcuType);
}

The following table explains the meaning of the three bytes signature code:

Address	Constant	Code	Valid codes
$00	SIGNATURE_0	Vendor code	$1E indicates manufactured by Atmel $00 indicates the device is locked
$01	SIGNATURE_1	Part family and flash size	$9n indicates AVR with 2^n kB flash memory
$02	SIGNATURE_2	Part number	identifies the exact chip in the family

A list with the signature codes of the most used Atmel (the company which produces the Arduino chip) MCUs is shown below:

MCU type	Signature code
ATtiny13	1E9007
ATtiny2313	1E910A
ATmega48P	1E920A
ATmega8	1E9307
ATmega168	1E9406
ATmega32	1E9502
ATmega328P	1E950F
ATmega328-PU	1E9514
ATmega64	1E9602
ATmega644	1E9609
ATmega128	1E9702
ATmega1280	1E9703
ATmega2560	1E9801