Tutorial 13 for Arduino: Liquid Crystal Displays (LCDs) Video Lecture | Arduino Programming: Step by Step (to become an Expert) - Electronics and Communication Engineering (ECE)

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everybody Jeremy Blum here with episode
13 of my artery on tutorial series
sponsored by element 14 this we're going
to be talking about liquid crystal
displays or LCDs as they're more
commonly known we'll be using a 16 by 2
character display the specific display
that I'm using today was supplied to me
to to review by element 14 it's a little
bit bigger and draws more power than
most LCD displays and has two extra pins
for heater on it all the schematics and
stuffs associated this episode are
showing you how to do with a more
standard 16 by 2 display just keep in
mind while I'm hooking line up that some
of the pins are kind of in a different
order but all the labels are the same so
it should make sense if you look at the
schematics for how to wire one up so
liquid crystal displays are great
because they allow you to untether your
project from your computer something
we've been doing with a lot of the
project in the past is sending data back
over serial to the computer so you can
then process it and do stuff with it but
if you have a display built right into
your device then you no longer need to
have the computer hooked up you can
bring your device with you and have it
display meaningful data to you and
that's really really useful so let's
talk a little bit about how our LCD will
interface with the Arduino and then
we'll hook one up and by the end of this
episode you'll have a nice little
project with an LCD a temperature sensor
and you'll be able to read Celsius and
Fahrenheit room temperatures alright
let's get started alright let's talk
about getting our and I'll see you
display hooked up all Elsie's 16 by 2
character displays basically the same
interface they're all going to be 16
pins of pin one here pin 16 here with a
number of logic lines and the power and
ground and an LED hookup and whatnot the
only other component that you're going
to need is a 10 to 20 K 10 10 XI ometer
I use a 10k breadboard mount
potentiometer and we'll use that to
control the contrast of the display so
some LCDs we'll put these in a different
order than I'm showing here this is a
pretty common configuration the LCD I'm
using today actually puts them in a
different order and adds two more pins
for a heater to help it operate
calling temperatures but I'm just not
going to use those I don't need to put
them up but this is this is a very
common configuration so let's talk about
how we're gonna hook this up first off
the LED backlighting we're just going to
give it 5 volts on LED plus we're also
gonna need 5 volts for the logic input
to the display and our potentiometer is
gonna be hooked across 5 volts and
ground and then into the display to
control contrast so we're going to need
the 5 volts up there so those are all of
our 5 volts signals on ground there's
gonna have to be the the other end of
the LED of course so that we can
actually light it up and you can
actually control the backlight with the
Arduino if you want if you want to turn
it on and off but I'm just gonna clip it
right up to 5 volts we're gonna need to
ground the logic for the actual display
and then grab the other end of the
camera the next thing here is the RW
logic pin so that means you can choose
whether you want to read or write to the
display ordinarily we have no reason to
read forever the LCD display we only
want to write data to it so we can
actually tie that to ground instead of
being yeah we don't need to control it
with the or by wasting and pin on the
Arduino so we can just try and write to
ground and not have to worry about it
that means we're setting it to always
write to the LCD next thing is the V not
pin so the V not pin allows us to set
the contrast of the display and that's
what our potentiometer is for it
so you'll hook the middle pin of the
potentiometer up to V naught like that
it's pretty straightforward
and then all of our other pins we're
going to use for sending data so we have
the RS pin that will go to one eye open
on the arduino the e or enable pin will
go to another pin on the Arduino now
there's eight data pins here zero
through seven what's interesting is that
you can actually just use four of them
and still try
and all the information you need and
then you often waste it you know the ten
total connections so um you know just to
drive this LCD so we are actually not
going to hook up D zero one two or three
we're just gonna hook up D seven D 6 D 5
and 4 so in total we're just gonna have
one two three four five six connections
going to the Arduino for control these
guys won't get hooked up we have our LED
backlight hooked up logic hooked up for
the LCD contrast took that for the
potentiometer and our W is just hooked
right to ground so we ready to go let's
get this wired up in program and we can
start showing some stuff on our screen
once you've got your circuit wired up
look a little bit something like this
now keep in mind that I have a high
power backlight in this one so I
couldn't power it off of you USB only I
had to plug into the wall also you won't
have to do that I also hadn't had a
resistive voltage divider here to get
the six volts for the LED backlight you
can just hook your LED backlight line
right in to five volts from the Arduino
so keep that in mind while you're
looking at this but once you turn it on
you should get something like this on
display and if you don't make sure that
you twiddle the contrast knob here
because that will allow you to the
adjust the brightness of the image and
you can see as I turn the knob it just
how dark the images so you want to kind
of somewhere in the middle and you'll
see once we have text on it
that's that level where you want so just
that somewhere good
your backlight should be on if you're
assuming your background is put into
five volts and you can see that mine
most definitely is and if I unplug it
you can see what it looks like it off
much darker and put it back in and it's
a nice and bright again so that's
basically it the data lines are hooked
up you can if you download the schematic
from my blog it'll show you exactly
which one I ride them into or in a
second we'll do it in the program
you'll be able to see which ones I have
tuned into my hooked it into two through
seven the order starting with the
control pins and then adding the data
pins so let's go ahead and get this
program so you can get something a
little bit more interesting on that
display open it's time to write a simple
example that worked test our LCD setup
first thing you should do is make sure
you credit the creators of the library
on top of your source code file press or
open source here and it's always nice to
give credit where credit is due because
these guys made an awesome-looking just
a library so be sure to give them a
shout in your source files here I'll
define the pin hookups that I'm going to
be using and there's the one that I just
showed you on the breadboard our
suntanned to enables on pin 3 and then
pins 4 through 7 on your Arduino
correspond to data pins 4 through 7 on
the LCD for convenience first thing
we'll need to do is include the liquid
crystal library which is what we'll use
to interface with the LCD so that's
called simply enough like crystal 5h so
you should include that and then once
you've included it you can make an
object with it so I'll call object the
LCD and the parameters for LCD are just
the pins that you're hooked up to in the
order that I've already listed them so
it's 2 3 4 5 6
semicolons ok next thing you mean I've
already written out because it's
relatively long or some custom
characters so if you take a look at the
sample display that I've already put
together you can see a nice little
progress bar going across the screen to
accomplish that I had to make custom
characters that fill up one pixel column
at a time on each of the 16 characters
we can animate them across and that's
what lets do right now so each of these
is a byte array that's 5 by 7 because
that's the number of pixels each of the
16 little boxes that go across the first
and second rows and the ones in zeros
here correspond litterateur which pixels
on so we can make this byte array the B
specifies these are binary values and
you can see the kind of progress bar
action happening here as the ones
cross and then we can use those
characters later on to make progress on
our animation so when we go down to the
set up now the first thing you want to
do is begin I'll see the interface just
like we begin stereo interface for
example do LCD dot begin a lowercase B
16 comma 2 and that's indicating that
there are 16 columns and two rows first
thing I'm going to do it put the cursor
by default at the beginning I'm going to
print out Jeremy's display by doing LCD
dot print and I'll see def print will
just print and he you know standard
characters numbers etc Jeremy use comma
Jeremy's apostrophe s display and this
happens to already be 16 characters so I
know that I'm good to go if it's not you
can add trailing spaces or you can just
make it less than 16 characters I'm
gonna take up the whole line that's
totally fine
the next thing we you do is actually
initialize each character the byte
arrays that may appear as characters
that we can send to the display so you
can only do sent number of these this is
less than that I don't know the exact
amount on my head it's in documentation
for the liquid crystal library but we
can do LCD duct create char and you know
you give it an incrementing number and
then whatever the byte array was that
you named it so I'll do that for each of
the byte arrays that I define the phone
also okay so those are charged now all
we have to do in the loop is basically
move across the bottom row and fill
these in line by line and then reset
them and do it over again and that'll be
in a big giant loop down here so the
first thing we need to do is I don't
actually have to do this the first time
around but after we've made the progress
bar it's going to be important to move
the cursor back to the beginning so that
we start writing stuff at the beginning
the second row again so to move the
cursor back to the beginning I'm gonna
do LCD dot sector 0 1 and so the first
thing here the 0 is specifying that
we're using the first column so these
are 0 index so 0 is the first column and
the 1 here indicates that we're using
this second row and that's that's a
little confusing but if you basically
just add 1 to it which it should make a
little bit more sense the next thing
we'll do is clear the line because we've
just finished our progress bar and we
want to start again so we'll do LCD yeah
print and I'm just going to print out to
16 spaces 1 2 2 4 5 6 7 8 9 10 11 12 13
14 15 16
okay all good and now we're just going
to do two nested for loops that handle
the outer nested for loop we'll go
through each of the 16 characters and in
the internet search for loop in each one
we'll print out the custom characters
percentages of each set that we defined
before and print those out in order so
that we get a nice progress bar effect
so we'll make our outer for loop first I
was 16 I plus plus so this is going 0
through 15 index you want to work with
and remember we need to be starting in 0
procedure 0 index of course here so that
will have limp and then inside that 4
you will have another for loop so at
each point in the outside for loop so
inside each position on the screen it
will make a new type of character so
we'll do or into J make sure you choose
different variable here that's very
important they don't interfere with each
other J less than 5
Plus so this is going in 0 through 4 in
other words the guys I'd if I appear
from that's actually a mistake number
yeah this will go through each of those
five guys up there so for loop so at
each position the first thing we do is
set our cursor there so that we know
that that's what we wanted right
that's the dentist's it first you buy
one so the eye is because we're at that
particular position on the bottom row
and the one is because we're on the
bottom wheel and then we're going to use
LCM right which is different from LCD
print and then we can use it to output a
custom character so we can write J so by
saying like for example the first time
to this will write or 0 which is custom
chart 0 which is our 20% line so that
will work out nicely and then of course
we're going to need it'll delay here so
this doesn't happen faster than we can
even see it
so let's just put a tenth of a second
delay that should be enough probably
okay so you know that works alright and
we can see that it the Arduino very
nicely and that we have a very nice
partners for our effect going across it
present my name on the first line and on
the bottom line you can see it goes
through and instead of just doing it
block by block and actually as it pixel
by pixel which adds a very nice effect
there ok cool so now let's make this a
bit more complicated and get it a
temperature sensor on there and a little
button to interface with and we'll have
this giving us our room temperature in
Celsius and Fahrenheit and we'll
actually have some interactivity out of
it all right here are my plans for our
revisions to our system to add a
temperature sensor a nice little readout
we already have these green lines hooked
up for the LCD these are the data lines
and then the control lines over here we
already have our pot hooked up but we're
going to add is ATC 74 I to see
temperature sensor we have
use this in previous tutorial number
seven where we learned about I to see
communication so you should already have
as part hopefully and so this just
communicates over the i2c bus to the
Arduino and the i2c plus is multiplexed
on analog ins 4 & 5 so we'll plug that
in just like I show in this schematic
here making sure that we have our 10k
pull-up resistors that go from those
communication lines up to our 5 volt bus
over here so this will sense the room in
degrees Celsius and report us that value
and then we can print out the
temperature here in degrees Celsius on
the LCD display in real-time but seeing
as how I live in America and we still
use this stupid thing that's called
imperial units it's nice to know the
temperature in Fahrenheit as well so
I've added a push button here and we'll
use the debouncing software that we
learned about in episode 2 to hook our
push button up to arduino as digital
input 8 and use that to switch between
Celsius and Fahrenheit modes and I've
intentionally positioned the push button
here right next to the screen because
we'll add a little indicator here on the
second row that says mode and it will
point to the button so that you know you
can press the button to change the mode
and that'll be a nice little setup and
then don't forget for that we have
another 10k this time acting as a
pulldown resistor so by default the
button is pulled through this 10k to
ground except when you push the button
down when it shorts goes to 5 volts and
then sends that value to the Arduino
where we debounce it and use it to
control our system so let's get this
program and then we'll get it wired up
and ready to roll so now we've got our
circuit design and I've I've already
gone ahead and put those changes on to
the breadboard that I'm using just
adding an i2c temperature sensor or some
pull-ups for it and the button is
basically all you need so that's already
set up just like I showed you in the
schematic and now it's literally a
matter of copying and pasting code from
episodes 2 and 7 so if you haven't
watched the episodes 2 & 7 go watch that
now if it'll make all of us make a lot
more sense because I'm not going to redo
stuff that we
already done so in Episode two we talked
about bouncing in seven we talked about
I to see interfaces so first thing we're
gonna do here I'll just walk you through
some of the changes I've made and then
we have to finish up the program
together so I've included wire dot H
which is the i2c library for
communicating with I'd feed chips like
our temperature sensor and we know from
the data sheet that the idea of our
temperature sensor is 72 so that's all
set up I got rid of our progress bar
custom characters and I actually made a
new custom character called degree
because we need a little degree symbol
for our Celsius and Fahrenheit and you
can see where the ones are it makes a
nice little degree circle up there that
we can use and now this is literally
copy and pasted from the debouncing code
in tutorial 2 I'm just setting the input
for the for what pin this with the
switch is connected to its pin 8 in this
case and I'm setting button States which
are boolean so true or false to low
initially for both them and then I'm
also just going to initially say that
we're gonna default to Celsius and then
it pushed it changes to Fahrenheit and
then change this back to cetera in the
setup I've specified the switch pin as
an input
began the wire library again this is all
straight from material 7 this is the
same as before I changed this to say
room temperature instead of Jeremy's
display just like before as well I now
move the cursor to the position 11 1 so
this is the second row position number
11 on there so the reason I did that is
remember I place the button immediately
to the right of the second row so this
gives us just enough room to write mode
with a little hair in essence that'll be
pointing directly at the button so you
know to press the button to change
between temperature modes just kind of a
neat little feature there and then just
like before we have to create our custom
chars in this case we only have one as
opposed to the 5 then we had last time
and it's called degree because that's
what like
the byte array up here so the only thing
that we have left to do now is to do our
loop the debounce function is already
written this is again the debounce
funking straight from episode two you
don't rewrite anything and this just
takes in the last button state and spits
out the current button state after be
bouncing it I've already added in the
lines that grab the temperature and put
it into Celsius and Fahrenheit from the
i2c temperature sensor because this too
is copied directly from tutorial seven
is it nice to have code that you already
have to work with it makes everything a
lot easier so all the only thing that we
have to do now is basically grab the
information about the button state and
then throw in what we want to have on
the display so we've got our
temperatures here let's write some
buttons switch code the first thing
we're going to do is get the current
state of the button using our debouncing
function then this too is exactly what
we had already done and it's a twirl -
so remember ready to find current button
up here as well as the last button so
we're developing the last button hit the
current quitting okay so if the the last
button was low and remember double + %
and hits a logical end the current
button is high so that means that
someone is currently like holding down
the button they just pushed the button
and this has already been be bounced so
we can now say okay that's the case
don't just push the button
so if Celsius is currently true which we
can we can make out an if statement in
here so this is shorthand for saying if
Celsius true you could also write equals
equals true but you don't have to
actually have
case you can do that but you can just
write something as simple as if Celsius
so if Celsius is true then we're gonna
set it equal to false which means we'll
be working in Fahrenheit mode otherwise
we regress that's true that okay and now
importantly we have to erase the old
character so you can write the new
temperature over them so we're gonna do
LCD dot set cursor and we're just gonna
write these at the first position on the
second row
that said cursor zero comma one just
like we did in the previous example and
LCD dot print we're gonna clear those
making sure however not to make this so
long that we clear our mode set up here
so instead of making a sixteen long this
is five characters up here so we need to
make this actually 11 long one two three
four five six seven eight nine 10 11 and
you actually can make it short in that
turn I can use all the spaces but I'll
just make it full size doesn't really
matter and now we're gonna set last
button equals to current button you
guess each time we've gone through the
loop you know we're now done with
current bun and that can be the next
time to loop it will be was within the
last button okay so that's done now we
actually you have to just print it to
the screen and that's pretty simple we
just look at whether it's Fahrenheit or
Celsius and print the corresponding
thing so well do LCD dot set cursor to
zero comma one at the beginning again
and then if Celsius will use the same
shorthand we used before then we'll do
LCD print we will print out the variable
then we would do house Twp right
remember that allows us to use our
special character so we'll print out the
degree sign which was numbers ID 0 and
then we'll do LCF print again and we'll
print the letter
see to guard for the agree sign perfect
and now we'll do the exact same thing
for Fahrenheit so otherwise it's
Fahrenheit LCD dot print the Fahrenheit
temperature then LCD dot write our
degree sign and LCD dot print our
Fahrenheit and this should actually be
text as well that's important because
it's not a variable any variable would
not have quotes around it and close off
our brackets here and that should do it
okay so make sure you have your own
traffic up there showing the schematics
and then let's see how this works oops
any space there alright so the programs
on there and it seems to be working
quite nicely you can see the current
room temperature is between 27 and 28
degrees Celsius just quite warm I have
my air conditioning turned off so that
you can actually hear me talking so I'm
basically torturing myself for you guys
so I hope you're enjoying this and if I
tap one it goes into Fahrenheit mode and
you can see it's been 81 or 82 degrees
fahrenheit in here and sure enough you
could go back and forth with relative
ease we have our nice mode thing that
does it disappear anything when we're
switching between modes and yeah it
works quite nicely and you can see over
here is our by 2 C temperature sensor
and everything else is wired up just
like it was before so very nice and you
can make just with anything you want
with this so go have fun and do some
cool projects with an LCD thanks for
watching this episode of my RDM tutorial
series I hope you guys enjoyed it I have
a review of the LCD readout that I use
on my blog you should go check it out if
you like the readout that I was using in
the demo today it's a little bit bigger
and more expensive than most LCD
displays but it has a really nice
contrast and a very bright backlight and
so if that's something you want it's
also very large that this might be the
display for you otherwise go check out
adafruit.com that's the link I'm going
to put in the parts list for this video
they have a more standard sixteen by two
I also see display it's smaller cheaper
and it comes with the header and the
contrast knob for adjusting it so you
should go check that out relatively soon
I'm going to be putting out a review for
a shield for the Arduino for attaching
an LCD display it's made by wicked
devices they send me one to review so
that will come out pretty soon and then
allow you to put the LCD right on the
Arduino so you can get something more
compact and a breadboard so look forward
to that and yeah that's about it so if
you have any questions comments etc feel
free to post them on this video on my
blog on the element14.com and i also now
have a facebook fan page which is a
little embarrassing but I do people kept
asking for it so I made one so you can
now like me on Facebook if that's your
thing and I'll try to update that with
the sort of information particularly
about one of these tutorials are coming
out and stuff and I have to have a
Google+ so you can go and be on Google+
if you now have that and the links are
both those are on the sidebar on my blog
so you can go check that out if you want
otherwise I will see you guys very soon
thanks again for watching thanks to
element14 for helping me to sponsor this
video series they were kind enough to
provide a lot of the materials that I'll
be using to create these tutorials
feel free to go visit their website at
element14.com check out their community
which is a great place to talk to you
about electronics they already we know
and basically anything else engineering
related and they also have a store where
you can buy a lot of the parts that
we'll be using in these videos
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