AVR128DB28 is the sucessor to the venerable ATmega328 and ATmega2560 MCUs so common in the Arduino.

The AVR128 offers 128K Flash and 16kBytes of SRAM

It has an internal Oscillator so does not require and external crystal - use programmable

from 1 - 24MHz ( overclockable to 36MHz )

The usual array of GPIOs and timers

multiple Serial Interfaces - 3 UARTs, 2 SPIs, 2 I2Cs

12 bit Analog Inputs ( ADC ) - 1 x 10but Analog Output ( DAC )

Real Time Clock

1.8V - 5.5 V operation - Dual Power Domain allow operation of individual GPIOs pins

at 3V3 or 5V for example - different Voltages may be supplied.

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The ATmega328P is very well known from Arduino UNO and Nano fame.

It offers 32k of flash and 2k SRAM

The bootloader can be flashed for different CPU clock frequencies.

Let me know if you want other than the standard external 16MHz, such as 20MHz external

or 8 MHz internal..