UNO R3 development board MCU mega328p / 2560 chip Ardu expert improved version ch340
UNO R3 is an easy-to-use open source controller. Compared with UNO, there is no major change in hardware.
The biggest difference lies in the USB to serial circuit part. Instead, an ATMega16U2 microcontroller is used,
which increases the cost. The software part As before, there are no major changes.
1. Pin changes: Two I2C pins are added next to the AREF pin (SDA and SCL are just copies of Analog 4 and 5,
not an additional I2C interface), and two pins are added next to RESET, one is IOREF , Can make the expansion
board adapt to the on-board voltage, this pin only tells the current on-board voltage of the expansion board
(for example, UNO is 5V, which can be regarded as a copy of the power pin and does not provide level pull-up),
and the other is for the future Placeholder pins to be used. 2. More stable RESET circuit. The position of the RESET button has also changed, and it has been moved to
the corner of the board near the USB interface, making it easier to press. 3. ATmega16U2 replaces 8U2. This does not mean that R3 with 16K flash can make your code run faster.
This update is for the USB interface chip. In theory, it allows UNO to simulate USB HID, such as MIDI/ Joystick/Keyboard.