> For the complete documentation index, see [llms.txt](https://ruggedboard.gitbook.io/ruggedboard/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ruggedboard.gitbook.io/ruggedboard/master/test-interfaces-of-rb/interfaces/uart.md).

# UART(Universal Asynchronous Receiver-Transmitter)

A **UART(Universal Asynchronous Receiver-Transmitter)** is a computer hardware device for asynchronous serial communication in which the data format and transmission speeds are configurable. The electric signaling levels and methods are handled by a driver circuit external to the UART. A UART is usually an individual (or part of an) integrated circuit (IC) used for serial communications over a computer or peripheral device serial port.

**Let us write and implement a test program for a UART.**

**Step 1: Create a uart.c File**

**Step 2: Write the following code into the File**

```
#include<stdio.h>
#include<stdlib.h>
#include<fcntl.h>
#include<termios.h>
#include<string.h>
int main(int argc, char * argv[])
{
	int fd;
	fd = open("/dev/ttyS3",O_RDONLY|O_NOCTTY);
	if(fd == -1)
	{
		printf("\n Error! in Opening ttyS3");}
	else{
		printf("\n ttyS3 Opened Successfully");}
	close(fd);
}
```

**Step 3: Open Terminal and navigate to your Toolchain folder**

**Step 4: Run the "env.sh" file using the command `. env.sh` to enable the Toolchain**\
**To make sure the toolchain is runnig type in "arm" and hit the \<TAB> key twice.**

**Step 5: To create a binary named uart from "uart.c"** \
`arm-linux-gnueabi-gcc uart.c -o uart`

**Step 6: Transfer the compiled binary to the Board using TFTP or SD card.**

**Step 7: Run the binary file** `sudo ./uart`**on the Board's Terminal.**