The ATMEGA328P-MU is an 8-bit AVR microcontroller from Microchip in VQFN-28 (5x5mm), running at 20MHz with 32KB Flash, 2KB SRAM, and 1KB EEPROM. It is the compact surface-mount version of the ATMEGA328P-PU used in the Arduino Uno, sharing the same die and peripheral set. The AVR core executes most instructions in a single clock cycle, achieving 20 MIPS at 20MHz. The 32KB Flash supports 10,000 write/erase cycles for bootloader and self-programming. The 10-bit ADC has 6 channels (on Port C) with 15ksps at maximum resolution and auto-trigger capability from timer compare matches or external events. Two 8-bit timers (Timer0/Timer2) and one 16-bit timer (Timer1) provide PWM generation (6 channels), input capture, and real-time clock (with 32kHz crystal on PB6/PB7). The USART supports serial communication at up to 2Mbps. The SPI port runs at up to 10MHz in master mode. The I2C/TWI interface supports master and slave at up to 400kHz. The -P suffix indicates picoPower technology: the device draws only 0.1uA in power-save mode (with RTC running) and 0.75uA in power-down mode. The VQFN-28 package provides 50C/W thermal resistance with exposed pad, allowing 800mW dissipation at 25C. The -MU suffix specifies VQFN-28, industrial temperature (-40C to +85C). This is the go-to MCU for compact Arduino-compatible designs.