sending data from a computer to a microcontroller

8/9/2019 Sending Data from a computer to a microcontroller

1/9

Page | 1

Sending Data from a computer to a microcontroller

using a UART (Universal Asynchronous

Receiver/Transmitter)

Eric Bell

04/05/2013

Abstract:

Serial communication is the main method used for communication between external

microcontrollers and computers, and can be a challenge to set up correctly. This application

note will provide a walk-through example on how to set up a simple UART communication link

using Microsoft Visual Studio and the Arduino Leonardo microcontroller.

Keywords:

Arduino, Leonardo, Visual Studio, Microcontroller, UART


2/9


3/9

Page | 3

Introduction:

This application note will provide instructions on how to obtain simple communications

between a computer and a microcontroller using UART (Universal Asynchronous

Receiver/Transmitter). UART is a commonly used piece of hardware which translates data

between parallel and serial communication mediums (See reference [6]). In this tutorial, you

will be taught how to set up a simple interface between a computer and a microcontroller by

utilizing Microsoft Visual Studio, and the Arduino Leonardo microcontroller.

The implementation described in this application note will provide a walk-through to set

up the Arduino Leonardo to receive communication from the computer and then respond

appropriately. In this case, the microcontroller will receive characters from the computer

consisting of either ‘+’ or ‘-‘. These characters will activate an LED by turning it on or off, by

interpreting a ‘+’ as an “on” signal, and a ‘-‘ as an “off” signal.

Implementation:

Hardware:

- Personal Computer running Microsoft Windows

- Arduino Leonardo Microcontroller

- Micro-USB Interconnect Cable

-

1 LED (any color)

-

1 220-Ohm resistor

Software:

-

Microsoft Visual Studio

- Arduino IDE Software

- Arduino Leonardo Drivers


4/9

Page | 4

Arduino Software Installation

Download and install the Arduino IDE Software and Arduino Leonardo Drivers by following the

set-up instructions provided with the software. Arduino IDE Software and Leonardo Drivers can

be obtained free of charge by download by visiting http://arduino.cc/en/Main/Software.

Hardware Setup

For this communications set-up, we will be physically connecting the Arduino Leonardo

microcontroller to the computer using a micro-USB interconnect cable, and setting up the

microcontroller to provide feedback through the lighting of an LED. The microcontroller can be

obtained by ordering, and is available at many different web sites on the internet. One major

distributor of Arduino products is Mouser, and this microcontroller can be ordered from them

by visiting www.mouser.com/Arduino-Leonardo.

Follow the steps outlined below for proper set-up:

1) Connect the 220-ohm resistor and LED to the Arduino Leonardo microcontroller by

following the diagram below. (See Reference [1])

2) Plug the Micro-USB cable in to the Arduino Leonardo in to the attached port, and in to

any available USB port on the computer.


5/9

Page | 5

Setting up the Receiver

The Arduino Leonardo microcontroller needs to be set up to receive a character from the USB

port, and also needs to be programmed to respond appropriately based upon the receivedcharacter. This will be accomplished by using the Arduino IDE Software and the following code

(See reference [1]):

int led =13;char c;

void setup(){

pinMode(led, OUTPUT); // specify led port as outputSerial.begin(9600); // Specify serial communications speed}

void loop(){

if(Serial.available() >0){

c =Serial.read(); // reads a character from serial interfaceSerial.print(c);

if(c =='+'){

digitalWrite(led, HIGH); // turn on LED}

else if(c =='-'){

digitalWrite(led, LOW); // turn off LED}}

}

The code above is written in C#, and will specify port 13 as the port for our LED, and will

determine whether the Arduino Leonardo will turn on or turn off the LED. Once this code has

been typed in to the Arduino IDE software, it can be uploaded by clicking on File-> Save, and

then clicking on the Upload button. The button is depicted as a small arrow in the upper left

corner of the program screen.


6/9

Page | 6

Setting up the Sender

For this portion of the set-up, we will be using Microsoft Visual Studio to create a program

which will send the ‘+’ or ‘-‘ character to the Arduino Leonardo microcontroller through the USB

cable. This portion of the application note will provide a demonstration on how to write code

that will:

1) Determine if there is a serial port currently available for communication

2) Open the serial port for communications

3)

Send data through the serial port

4) Close the serial port

Microsoft Visual Studio should be used to create a new project, in which you should create one

combo-box, and four buttons. This can be accomplished within the program by clicking on The

toolbox icon on the left side of the screen, and then double-clicking on the Button link. This will

allow you to place the button on your blank form. Once all buttons have been placed, double-

click on the ComboBox link in order to place the drop-down menu as shown in the figure.

Complete instructions are included in the Microsoft documentation on their web site

(Reference [4]). When complete, your program GUI (Graphics User Interface) should look

similar to this:

The code on the following pages will then be used to control the functions of the combo-box

and buttons.


7/9

Page | 7

Example code to determine if t here is a serial por t current ly available (See reference [2]) :

private void Form1_Load(object sender, EventArgs e){

foreach (string port in SerialPort.GetPortNames()) // Adds all port names toports list{

cbPorts.Items.Add(port); // adds ports to Ports combo-box}

if (cbPorts.Items.Count >0) // if there is at least one port available, select thefirst one as default

{cbPorts.SelectedIndex =0;

}else // no ports available

{cbPorts.Enabled =false;MessageBox.Show("Could not locate any available serial ports.", "No serial

ports", MessageBoxButtons}

btnSendA.Enabled =false;btnSendB.Enabled =false;btnClose.Enabled =false;

}


8/9


9/9

Page | 9

In this application note, we have covered the set up of the hardware, the design and

programming of the user interface, as well as the programming of the Arduino Leonardo

firmware. By following these instructions, it should be a very straight-forward task to develop

communication between the computer and the Arduino Leonardo microcontroller. Once these

techniques have been practiced, they can be applied to more complex situations, as well as to

other microcontrollers.

Recommendations

- The Arduino Leonardo can also be used to send date to the computer using the

serial interface. There are many examples and tutorials available for free by utilizing

the Arduino web site. (See reference [1])

- The serial ports on the Arduino Leonardo can be used to communicate to more

complex devices, such as other microcontrollers

-

More complex Arduino Microcontrollers are capable of communication through a

much wider array of communication mediums, such as WiFi, rather than just serial

communication

References

[1] http://arduino.cc/en/Tutorial/HomePage

[2] http://msdn.microsoft.com/en-us/library/tf8zk72w.aspx

[3] http://msdn.microsoft.com/en-us/library/y2sxhat8.aspx?cs-save-lang=1&cs-lang=csharp#code-snippet-2

[4] http://msdn.microsoft.com/en-us/vstudio/aa718325.aspx

[5] http://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter

sending data from a computer to a microcontroller

Documents