UNO R3 board

PWM output:

3, 5, 6, 9, 10, 11, can be used to output 8-bit PWM wave. Corresponds to the function analogWrite() .

SPI:

10(SS), 11(MOSI), 12(MISO), 13(SCK), can be used for SPI communication. It can be manipulated using the officially provided SPI library.

L-LED:

13. An LED is connected to pin 13, which turns on the LED when the pin outputs a high level, and turns off the LED when the pin outputs a low level.

TWI:

A4 (SDA), A5 (SCL) and TWI interface, can be used for TWI communication, compatible with I²C communication. Can be manipulated using the officially provided Wire library.

Arduino Uno 6 analog input pins, analog values ​​can be read using analogRead(). Each analog input has 10-bit resolution (ie 1024 distinct values). By default, the analog input voltage range is 0 to 5V, other reference voltages can be set using the AREF pin and the analogReference() function.

The relevant pins are as follows:

AREF:

Analog Input Reference Voltage Input Pin.

Reset:

Reset the port. Connecting to a low level will reset the Arduino. When the reset button is pressed, the port will be connected to a low level, which will reset the Arduino.

Indicator (LED)

Arduino UNO has 4 LED indicators, the functions are as follows:

ON:

Power Indicator. When the Arduino is powered on, the ON light will light up.

TX:

Serial port sending indicator. The TX light is on when it is connected to a computer using USB and the Arduino is transmitting data to the computer.

RX:

Serial port receiving indicator. When connected to a computer using USB and the Arduino receives data from the computer, the RX light will be on.

L:

Programmable control indicator light. The LED is connected to pin 13 of Arduino through a special circuit. When pin 13 is high or high impedance, the LED will light up; when it is low, it will not light up. The LED can be controlled to turn on and off through a program or an external input signal.

communication

Arduino UNO has a variety of communication interfaces that can communicate with computers, other Arduinos or other controllers.

The ATmega328 provides UART TTL (5V) serial communication on pins 0 (RX) and 1 (TX). The ATmega16U2 on the Uno will simulate a USB serial port on the computer, so that the ATmega328 can communicate with the computer. The Arduino IDE provides a serial monitor, which can be used to send and receive simple text data. The two LEDs RX\TX on the Uno can indicate the current communication status of the Uno.

The SoftwareSerial library can simulate any digital pin of the Uno into a serial port for serial communication.

The ATmega328 also supports I2C (TWI) and SPI communication. The Wire library that comes with the Arduino IDE can be used to drive the I2C bus, and the SPI library that comes with it can be used for SPI communication.

Automatic reset

Some development boards need to be reset manually before uploading the program, but the design of the Arduino Uno does not require this. After the Arduino Uno is connected to the computer, the reset can be controlled by the program. The DTR signal terminal on ATmega16U2 is connected to the reset pin of ATmega328 through a 100nf capacitor.

When the computer sends out the DTR signal (low level), the reset terminal will get a pulse signal long enough to reset the ATmega328. Click to upload the program in the Arduino IDE, and the reset will be triggered before uploading, so as to run the boot program and complete the program upload.