Department of Electromechanical Engineering
Workshop for Mechatronics
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Interfacing
1 Introduction
2 Display LED
3 Push button and LED with Arduino
Pull-up circuit
4 7-Segment Display
Programming 7 segment display without Library
Programming of 7-Segment Display Using SevSeg Library
5 Interfacing of Keys
Arduino Programming of Keypad
6 Liquid Crystal Display (LCD)
Temperature sensor and LCD
7 Analog Input Output
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Introduction
Introduction
Interfacing is the process of connecting devices together so that
they can exchange the information and that proves to be easier
to write the programs. There are different type of input and out-
put devices as for our requirement such as LEDs, LCDs, 7segment,
keypad, motors and other devices.
Microcontrollers are useful to the extent that they communicate with
other devices, such as sensors, motors, switches, keypads, displays,
memory and even other micro-controllers.
Many microcontroller designs typically mix multiple interfacing meth-
ods. In a very simplistic form, a micro-controller system can be
viewed as a system that reads from (monitors) inputs, performs pro-
cessing and writes to ( controls ) outputs.
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Introduction
Microcontroller Interfaces
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Introduction
Microcontroller Interfaces
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Display LED
Display LED
LEDs are most commonly used in many applications for indicating
the output. They find huge range of applications as indicators during
test to check the validity of results at different stages. They are very
cheap and easily available in a variety of shape, color and size.
The principle of operation of LEDs is very easy. A simple LEDs
also servers as a basic display devices, it On and OFF state express
meaning full information about a device.
The common available LEDs have a 1.7v voltage drop that means
when we apply above 1.7V, the diode conducts. The diode needs
10mA current to glow with full intensity.
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Display LED
LEDs can be interfaced to the microcontroller in either common
anode or common cathode configuration. Here the LEDs are con-
nected in common anode configuration because the common cath-
ode configuration consumes more power.
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Push button and LED with Arduino
Push button and LED with Arduino
This lesson will teach you how to control LED using a push button,
which stays on as long as the button is being pressed.
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Push button and LED with Arduino
The following figure is the protues and arduino code for push button
and LED with Arduino.
When your button is not pressed, the internal pull-up resistor con-
nects to 5 volts. This causes the arduino to report ”1” or HIGH.
When the button is pressed, the arduino pin is pulled to ground,
causing the arduino report a ”0”, or LOW.
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Push button and LED with Arduino
Pull-up circuit
pull-up circuit
when the switch is open the voltage of the gate input is pulled up
to the level of Vin . when the switch is closed, the input voltage at
the gate goes to ground.
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Push button and LED with Arduino
Pull-up circuit
RGB Programming
The RGB LED can emit different colors by mixing the 3 basic colors
red, green and blue. So it actually consists of 3 separate LEDs red,
green and blue packed in a single case.
That’s why it has 4 leads, one lead for each of the 3 colors and one
common cathode or anode depending of the RGB LED type. In this
tutorial I will be using a common cathode one.
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Push button and LED with Arduino
Pull-up circuit
The cathode will be connected to the ground and the 3 anodes will
be connected through 220 Ohms resistors to 3 digital pins on the
Arduino Board that can provide PWM signal. We will use PWM for
simulating analog output which will provide different voltage levels
to the LEDs so we can get the desired colors.
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Push button and LED with Arduino
Pull-up circuit
We will use PWM for simulating analog output which will provide
different voltage levels to the LEDs so we can get the desired colors.
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Push button and LED with Arduino
Pull-up circuit
RGB Arduino Programming
I will use the pins number 7, 6 and 5 and I will name them redPin,
greenPin and bluePin. In the setup section we need to define them
as outputs.
At the bottom of the sketch we have this custom made function
named setColor() which takes 3 different arguments redValue, green-
Value and blueValue. These arguments represents the brightness of
the LEDs or the duty cycle of the PWM signal which is created using
the analogWrite() function.
These values can vary from 0 to 255 which represents 100% duty
cycle of the PWM signal or maximum LED brightness.
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Push button and LED with Arduino
Pull-up circuit
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Push button and LED with Arduino
Pull-up circuit
So now in the loop function we will make our program which will
change the color of the LED each second.
In order to get red light on the LED we will call the setColor()
function and set value of 255 for the redValue argument and 0 for
the two others. Respectively we can get the two other basic colors,
green and blue.
For getting other colors we need to mix the arguments values. So for
example if set all 3 LEDS to maximum brightness we will get White
color and we will get a purple color if we set the following values to
the arguments: 170 redValue, 0 greenValue and 255 blueValue.
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7-Segment Display
7-Segment Display
Seven segment display is the most basic electronic display. It consists
of eight LEDs which are associated in a sequence manner so as to
display digits from 0 to 9 when proper combinations of LEDs are
switched on. A 7-segment display uses seven LEDs to display digits
from 0 to 9 and the 8th LED is used for dot.
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7-Segment Display
7-segment displays are used in a number of systems to display nu-
meric information. Thus the number of segments used depends on
the number of digits to display. The digits 0 to 9 are displayed
continuously at a predefined time delay.
7-segment displays are available in two configurations which are
common anode and common cathode. Common anode configu-
ration is used because output current of the microcontroller is suffi-
cient enough to drive the LEDs. 7-segment display works on negative
logic, we have to provide logic 0 to the corresponding pin to make
on LED glow.
In a common cathode configuration, all seven LEDs plus a dot LED
have the cathodes connected to pins 3 and pin 8. To use this display,
we need to connect GROUND to pin 3 and pin 8 and, and +5V to
the other pins to make the individual segments light up.
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7-Segment Display
The following table shows the hex values used to display the
different digits.
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7-Segment Display
Programming 7 segment display without Library
Programming 7 segment display without Library
The pins of seven-segment display are connected to Arduino pins
2-9, as shown in the table below. Common pins (pin 3 and pin 8)
are connected to GND and dp is left unconnected, because it is not
used in this experiment
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7-Segment Display
Programming 7 segment display without Library
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7-Segment Display
Programming 7 segment display without Library
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7-Segment Display
Programming of 7-Segment Display Using SevSeg Library
Programming of 7-Segment Display Using SevSeg Library
We will use the library called SevSeg to control the display. The
library works with single digit and multi-digit seven segment display.
You can download the library’s ZIP file from GitHub.
To install it, open the Arduino IDE, go to Sketch >include Library
>Add.ZIP Library, then select the SevSeg ZIP file that you down-
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7-Segment Display
Programming of 7-Segment Display Using SevSeg Library
Function Discription of SevSeg Library
sevseg.begin(): Its a function which initials the display
hardwareConfig = COMMON CATHODE ; this sets the type of dis-
play. I am using a common cathode, but if you are using a common
anode then use COMMON ANODE instead.
byte numDigits =1; this sets the number of digits on your display.
I am using a single digit display, so I set it to 1. if you are using a
four digit display, set this to 4.
byte digitPins[] = {} ; create an array that defines the ground pins
when using a 4 digit or multi-digit display. Leave it empty if you
have a single digit display. For example, if you have a 4 digit display
and want to use Arduino pins 10, 11, 12 and 13 as the digit ground
pins, you would use this:
byte digitPins[] = {10, 11, 12, 13};
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7-Segment Display
Programming of 7-Segment Display Using SevSeg Library
byte segmentPins[] = {6, 5, 2, 3, 4, 7, 8, 9}; This declares an array
that defines which Arduino pins are connected to each segment of
the display. The order is alphabetical(A,B,C,D,E,F,G,DP where DP
is the decimal point). So in this case, Arduino pin 6 connects to
segment A, pin 5 connects segment B, and so on.
resistorsOnSegments = true; This needs to be set to true if your
current limiting resistors are in series with the segment pins. If the
resistors are in series with the digital pins, set this to false. Set this
to true when using multi-digit displays.
sevseg.setBrightness(90); This function sets the brightness of the
display. It can be adjusted from 0 to 100.
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7-Segment Display
Programming of 7-Segment Display Using SevSeg Library
sevseg.setNumber();This function points the numaber to the display.
For example, sevseg.setNumber(4); will print the number ”4”to the
display. You can also print numbers with decimal points. For exam-
ple, to print the number ”4.999”, you would use sevseg.setNumber(4999,
3);The second parameter(the 3) defines where the decimal point is
located. In this case it is 3 digits from the right most digit. On
a single digit display, setting the second parameter to ”0” turns on
the decimal point, while setting it to ”1” turns it off.
sevseg.refreshDisplay();This function is required at the end of the
loop section to continue display the number.
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Interfacing of Keys
Interfacing of Keys
Keypad is a widely used input device with lot of applications such
as telephone, computer, ATM, electronic lock etc. A keypad is used
to take input from the user for further processing. Here a 4 by 4
matrix keypad consisting of switches arranged in rows and columns
is interfaced to the microcontroller.
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Interfacing of Keys
Every number of keypad is assigned two unique parameters that are
row and column. Hence every time a key is pressed the number is
identifying by detecting the row and column numbers of keypad.
Initially all the rows are set to zero (’0’) by the controller and columns
are scanned to check if any key is pressed. In case of no key is pressed
the output of all columns will be high (’1’).
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Interfacing of Keys
Arduino Programming of Keypad
Arduino programming of Keypad
Keypad is a library for using matrix style keypads with arduino.
getKey(): Returns the key that is pressed.
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Liquid Crystal Display (LCD)
Liquid Crystal Display (LCD)
LCD stands for liquid crystal display which can display the characters
per line. Here 16 by 2 LCD display can display 16 characters per
line and 2 lines. Each character is displayed in 5*7 pixel matrix.
LCD is very important device which is used for almost all auto-
mated devices such as washing machines, an autonomous robot,
power control systems and other devices. This is achieved by dis-
playing their status on small display modules like 7-seven segment
displays, multi segment LEDs etc. LCDs have reasonable price, eas-
ily programmable and they have no limitations of displaying special
characters.
It consists of two registers such as command/instruction register
and data register.
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Liquid Crystal Display (LCD)
The command/instruction register stores the command given to
the LCD. A command is an instruction which is given to the LCD
that perform a set of predefined tasks like initializing, clearing the
screen, setting the cursor posing, controlling display etc.
The data register stores the data to be displayed on LCD. The
data is an ASCII value of the characters to be displayed on the
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Liquid Crystal Display (LCD)
Operation of LCD is controlled by two commands. When RS=0,
R/W=1 it reads the data and when RS=1, R/W=0, it writes (print)
the data.
LCD uses following command codes:
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Liquid Crystal Display (LCD)
Example: LCD Interface
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Liquid Crystal Display (LCD)
Temperature sensor and LCD
Temperature sensor and LCD
The LM35 series are precision integrated-circuit temperature devices
with an output voltage linearly proportional to the Centigrade tem-
perature
The accuracy specifications of the LM35 are given with respect to
a simple linear transfer function:
mv
Vout = 10 ◦ ∗ T
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Liquid Crystal Display (LCD)
Temperature sensor and LCD
where
Vout is the LM35 output voltage
T is the temperature in degree centigrade
The LM35 device has a very wide 4-V to 30-V power supply voltage
range, which makes it ideal for many applications
The hardware connection is given as follows
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Liquid Crystal Display (LCD)
Temperature sensor and LCD
The protus simulation connection and the arduino code is given
below
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Analog Input Output
Analog Input Output
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Analog Input Output
Example of analog Interface
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