ATmega8U2/16U2/32U2 Datasheet, Pinout, Minimal Circuit

The ATmegaXXU2 devices are dominated by their USB 2.0 full-speed engines. Most other peripherals are cut back in favor of the added USB support. They make perfect USB to Serial converters because of this, since the price is quite low for the feature set. Primarily intended for USB to ... conversion, they feature a USART with RTS and CTS support, and one full 8-bit port (PORTB). PORTD is used for the serial port.

The main feature of the ATmega8U2/16U2/32U2 MCU's is the USB 2.0 engine. It is the basis for the USB to TTL converter for the R3 series Uno and Mega 2560 boards. There is no ADC section, and little I/O in general. A perfect use would be a USB to parallel, USB to Serial TTL, USB to SPI, etc.

Power Supply vs. Maximum Frequency

The calculator below provides a way to find the maximum operating frequency for any valid power supply voltage (2.7 to 5.5). Enter the power supply voltage and click "Calculate Max Frequency" to find the ATmega32U2's specified maximum clock speed at your Vcc.

Maximum Frequency Calculator for ATmega8U2/16U2/32U2

ATmega8U2/16U2/32U2 Features
Feature8U216U232U2
Flash 8k16k32k
EEPROM 0.5k0.5k1k
RAM 0.5k0.5k1k
I/O Pins 22
Interrupts 29
USARTS 1
USI 0
SPI 1
TWI 0
ADC Channels 0
RT Counter (w/osc)0
Timers (8-bit) 1
Timers (16-bit) 1
PWM (8-bit) 2
PWM (16-bit) 3
USB 2.0 Engine 1
Price (1's) $3.78$3.80$4.50
CharacteristicValue
Power Consumption (approximate) 5.5mA + (0.5/MHz)
Maximum I/O Current (per pin) 40mA
Maximum I/O Current (all ports) 100mA(low)/150mA(high)
Maximum I/O Current (total) 200mA (PDIP)
Maximum I/O Current (total)400mA (PDIP/QFP/MLF)

ATmega8U2/16U2/32U2 Datasheet

Link to ATmega8U2/16U2/32U2 datasheet from Atmel's website.

ATmega8U2/16U2/32U2 Pinout

ATmega32U2-MU pinout

ATmega8U2/16U2/32U2 "Minimal" Circuit Diagram

A minimal ATmega8U2/16U2/32U2 circuit consists of an ATmega8U2/16U2/32U2 and a few external parts. Because there are two ways this can be connected, bus-powered or self-powered, there are two drawings.

ATmega8U2/16U2/32U2 bus-powered minimal schematic diagram

ATmega8U2/16U2/32U2 self-powered minimal schematic diagram

In the self-powered configuration the program needs to know if the USB is powered or not. Use PC2 for that, or any pin you feel like using. The reset circuit could be anything, but there is an internal register that will allow the USB to reset the MCU, so there are choices to make.