Arduino Serial Communication Port Test Example with write and begin Function

Arduino Serial Port Communication

Arduino Serial Communication is used to communicate over serial port with terminal devices over UART like PC.

Understanding the serial communication in the Arduino is very important because these days many devices uses UART interface, like GPS, ESP8266, GSM and RFID modules.

The UART serial communication is a full duplex, means the devices have different data lines for send and receive signals.

Most of the time send line is marked as TX (Transmit Signal) and receive line is marked as RX (Receive Signal).

Figure 1 below shows the connection diagram of Arduino with PC serial port.

The UART communication is a “Asynchronous Communication”, means both devices does not share the common clock. Both devices having there own clock, but the timing must be same. The clock generator shown in the figure 1 generate the same baud rate clock.

The speed of communication is measured in bits per second and it is also known as the “Baud Rate”. Both of the devices must have same baud rate for proper communication.

Arduino Serial Begin and Baud Rate

Arduino library having a function called begin to set the baud rate and initialize the serial port. Mostly this begin function is called in the setup() function.

Arduino Serial write

Arduino library have a function called write which will send the data over the serial TX pin.

Arduino Send Data with write Function Example Code

Arduino serial send test code shows how to use both the function begin and write.

/*
	Arduino serial send test code  
	https://elextutorial.com
	This code will send "B" to the PC with a delay of 2 seconds.
*/

void setup() 
{
	Serial.begin(9600);//Set the baud rate 9600
}

void loop() 
{
    Serial.write("B");   // send A out serial
    delay(2000);   // wait for 2 seconds to send again
}
				 

Arduino Serial Test on Serial Monitor Window

Arduino IDE software have a built-in serial terminal small tool to test the communication project. It is known as Serial Monitor.

To start the Serial Monitor go to the menu Tools > Serial Monitor. Arduino Uno have on board USB to Serial converter like CP2102 or CH341.

If everything works perfect serial receive window shows BBBB, with a delay of 2 seconds in between new or next B. Shown in the below figure 3.