Tutorial 07 for Arduino: I2C Communication and Processing Video Lecture | Arduino Programming: Step by Step (to become an Expert) - Electronics and Communication Engineering (ECE)

hey everyone Jeremy Blum here with
Arduino tutorial number seven sponsored
by element14 this week I'm going to be
talking about the I squared C bus also
known as the i2c bus or the inter
integrated circuit bus in addition to
that we're also going to play around
with processing a little bit more which
we started using last week and at the
end of this episode we'll make an i2c
temperature sensor powered thermometer
that displays the temperature in your
room in Celsius and in Fahrenheit on
your computer screen and a nice little
readout and it should be really cool so
let's get started and learn a little bit
about I squared C here's a rundown of
how we're going to set up I squared C in
our circuit the Arduino we configured as
our I squared C master and the
temperature sensor we configure as our I
squared C slave you can have several
slaves on the same line and an I squared
C circuit as long as the you type in
different IDs the ID comes
pre-configured on the integrated circuit
at the time of purchase you can
sometimes request to have a special ID
preset or you can buy them with IDs
already set into them in this case we're
using one with an ID of 72 there's a
shared data and clock line between all
devices on the bus so what that means is
that you can communicate with several
devices but only be using two wires to
do so communication happens in both
directions on the SDA line on the
Arduino the SDA line is connected to
analog input for and the SCL line is
connected to analog input v basically
when you initialize the I squared C
interface in the Arduino it takes over
those inputs they can be used for more
than just analog input the other
important thing to remember with I
squared C is that you need pull-up
resistors I squared C is active low
which means the values need to be pulled
low to be considered a logic one so we
use a 10k resistor to pull both lines up
to 5 volts that they default to a 5 volt
signal we're not being pulled down by
the master/slave in order to get our
Arduino communicating the temperature
sensor the first thing we'll have to do
is have it specifically asked to talk to
ID number 72 this is so that we don't
get interference from anything else that
we have on the bus although in this case
we'll only have a temperature sensor
connected this particular temperature
sensor is configured to store the
temperature in the room in degrees
Celsius in register 0 so the next thing
we'll do is ask for the data in red
to 0 next we'll stop talking and then
wait for one bite response to come from
the slave or ID 272 that one bite
response will contain the temperature in
the room and degrees Celsius once we've
received that response we'll be able to
do whatever we want with it and send it
to the computer to do all kinds of cool
stuff with before we can get our I
squared C temperature sensor hooked up
we'll have to see what the pinata is on
it so that we can connect it to our
microcontroller to do this just search
the part number that you find on the
component on the component it says TC
seven for a zero so you just type it
into Google and we can see that the
first thing that comes up is a PDF with
datasheet of the device excellent
alright we want to look for the pin out
here it is this is a five pin device and
we're using the dip version not the
surface mount version here so we can see
it the first pin there is NC or no
connection then the data line the ground
line the clock line and the voltage line
so let's get that hooked up here we have
the I squared C temperature sensor all
wired up to the arduino note that i have
the power and ground rails heading over
to the power and ground rails on the
breadboard and i have the appropriate
pins on the I squared C hooked up to
power and ground also note that the
clock line from the I squared C
temperature sensor is connected analog
input v and the data line is connect the
analog input for as is specified on the
Arduino website if you look up the I
squared C interface also note that I
have the 10k resistors connecting
between the data and clock lines to the
five volt rail as pull-up resistors now
let's get this programmed now it's time
to write a simple program that will grab
our Celsius data from the I squared C
temperature sensor and send it to the
computer so the first thing we'll do is
import our I squared C library which an
Arduino is called the wire library so
we'll import wire dot H and remember
there's never any semicolons after and
included unlike everything else and
let's set our temperature address which
remember was 72 for our sensor temp
address equals 72 okay in our setup
we're going to need to make sure that we
our serial connection because we'll be
talking back to the computer same as
always
and we'll also have to do wire dot begin
which we'll learn initialized little
listening on the I squared C
communication bus okay I've already
outlined everything that we need to do
in the loop so let's just fill it in the
first thing we're going to do is start
talking to the I squared C temperature
sensor the commander to do that is
called begin transmission begin
transmission and we have to input the
address that we'll be talking to which
we stored up above so that I'll start
talking to it that will let it know that
that's the ID we want to talk to the
next thing is going to do is going to
send a zero to it to ask that it ask it
for the information in register number
zero so we'll do wire dot sin and we're
going to send it a zero okay we're now
done transmitting to it and all we're
going to do now is wait to get
information back so let's end the
transmission so we started the
transmission two lines earlier and now
we're going to end it using a similar
command although you don't need specify
the ID this time because it's already
connected to an ID okay
now we're going to be waiting to get one
byte back so we'll do wire dot request
from and the temperature address and the
amount that we want to get back which is
one point okay now we just wait so we
wait for a response here and this is
just like we did last time we're going
to put it in an infinite while loop that
will keep repeating until we get the
information that we want so we're going
to do wired out available this is just
same as with serial equals zero and wait
for our answer and when we do get the
answer that will be our temperature and
I'll set it to the variable C for
Celsius so we'll do wire dot receive and
we'll get the temperature okay now let's
keep going here we also want to get
temperature in Fahrenheit which we can
do a simple mathematical equation if you
don't know the conversion from Celsius
to Fahrenheit just google it it's very
simple and we'll set that equal to F for
Fahrenheit
so the equation for head first off we're
going to round it so that we get an
integer because in general you're
probably not going to get integer when
you convert from Celsius to Fahrenheit
so you to do that you multiply C by 9.0
/ 5.0 + 30 2.0 and the reason I'm doing
9.0 5.0 + 30 2.0 instead of not having
the decimal places there is because we
know that we're probably going to get a
number that's not an integer when we do
this and we want to make sure we're
multiplying it by other numbers that are
also floats so that we don't lose any
data and that's what adding the point to
it but the point 0 accomplishes now
let's just print the results to the
screen serial dot print first we'll
print to the Celsius address then we
will print the C to indicate that it's
in Celsius and we put a comma after it
so we can print Fahrenheit so note that
I'm not doing println I'm just doing
print this ensures that we all have a
character turn after it so it'll print
out the number and then the letter C
followed by comma right after it and
then after that we'll do serial dot
print and will print the temperature in
Fahrenheit and then we'll print in
capital F to indicate our unit of
measurement and now so it's easier to
read we can make this last one print
line so that it goes to the next line
afterwards okay and then just let's do a
delay so we can actually read what's
coming up on the screen in a reasonable
amount of time to delay 500 okay let's
see how this works so now we have the
program uploaded the Arduino let's see
what happens when I squeeze the
temperature sensor and heat it up
alright perfect the temperature goes up
from 25 C to 2060 or 77 to 79 Fahrenheit
I guess it's pretty hot in my room it
must be all the computer equipment
that's running right now ok great now
let's make this display something really
awesome on the computer instead of just
in the terminal window the first thing
we'll do to accomplish that is we're
going to get
the line break here and we're going to
replace it with a period and this will
just make it a little bit easier to
delineate between the information when
we bring it into processing so let's
let's get that on to the Arduino and
then we'll go into processing and do
some awesome stuff to make it look
pretty now we're going to create a
processing program that can grab the
data over serial break it apart into the
important parts and then display those
parts on the screen and pretty looking
text the first thing you want to do is
create a font that processing can use to
display the text on the screen go to
tools and hit create font in the
processing control window choose any
font you want I'm going to choose agency
F be bold because I think it looks good
and I'm going to make it big size 200
font this will automatically make the
font you need you might want to copy
this font name because we're going to
need it in a second and then hit OK okay
we quitted defined now let's get this
program set up I've already written some
of it for us the first thing is you're
going to import the serial controller
just like we did last time and you're
going to create a new serial object with
named port these are the variables that
we're going to use temperature C will
hold the temperature in degree Celsius
temperature F will hold the temperature
in degrees Fahrenheit data will hold the
entire string that comes in over serial
so that we can break it apart into the
pieces we want index will represent the
location in the string where the comma
is the comma will represent the disc the
difference between Celsius and
Fahrenheit so that we can find that and
then we're going to make a new font of
called font of type P font or processing
font and that's what we'll need to write
the text on the screen okay so I'm going
to make a new canvas of size 400 by 400
this is similar last time and setup our
port 9600 baud on comm 3 okay the first
thing we're going to do here is tell the
port to keep looking until it gets to
the end which remember we denoted with a
period so we'll do buffer until and then
we'll look for that period that's how
it'll know it's time to move on to the
next one okay now we're going to set up
that font that we just created
so we'll do font equals load font
and remember you can find all this
information on the processing website
this is how I figured out how to use the
all the font commands I just went to
their website and now I'm going to paste
in that thing I just copied and make
sure you put dot vlw at the end of it
cuz that's the file type put it in
double quotes so what that's doing is
that setting our font that we set up
here do have this font so we have that
setup and now we're going to call text
font on that choose the font that we
just set up and the size this is
actually optional because I already said
it 200 but I'm just going to do it
anyway just for fun okay in the draw
remember draw keeps getting refreshed
repeatedly to draw an image on the
screen we're going to start off with a
background of 0 0 0 which is just black
will keep the background black the fill
command will change the color of the
next object that we make you can figure
out how you want to choose these RGB
color values by just going online and
looking for an RGB color selector that
will let you pick out a color and it'll
basically return these three values this
is the amount of red the right of green
and the amount of blue so that's the
color I've chosen for the first one
you'll be surprised and see what it
looks like and to make that first one
now that we've chosen for the color for
it we're going to run text we're going
to print out temp C which we're going to
remember we're going to grab later but
it starts off as an empty string
remember you have to initialize it to an
empty string so that's this doesn't
throw an error the first time it runs
and then the next two parameters are
just the coordinates on the screen I
just kind of guess and checked until I
found that these parameters worked and
put it more or less in the center but
you can adjust those to ever you want
this is the x coordinate and this is the
y coordinate next we're going to set up
our fill for the Fahrenheit temperature
which will go right below the Celsius
temperature so for that I chose 0 102
153 which is a different color than
above of course and then we'll generate
that text based on the content of our
temperature Fahrenheit that we're going
to figure out how to grab in just a
second
so that'll be temp underscore F
73-70 are they coordinate that I found
worked okay and note how the
x-coordinates are the same for both we
want them to be left-justified
all right great now all we have to do is
write our serial port event which is
going to do something whenever we
basically get that buffer it's going to
do whatever comes before that buffer
okay so the first thing we'll do is
we'll use that data variable that we set
up earlier to grab the entire stream
that comes in so we'll set data equal to
port dot read string until and just like
before make sure you have the same value
here as you do up here we're going to
read the string until we get up to that
dot next up when you do read straight
until it actually includes the dot but
we don't actually want to show the dot
in our text so we're going to do
something called the substring and what
that's going to do is we're just going
to reset data to be the same thing
without the dot on the end so you can
run data dot substring 0 to data dot
length minus 1 and all this command does
is it basically removes the period from
the end of the data string and we know
there's always going to be a period
there of course this just says start at
the first character and go to the last
character minus 1 and that's what
creates the new data string ok so now we
have we're gone with our period which is
what we want now we want to look for our
comma so remember always comment your
code and we'll do index remember we set
index up here index is going to be the
location in the string of our comma you
can think of a string as a list of
individual characters each character has
a location in the string that's called
its index index will be data dot index
of which is a function that finds the
comma into our string so that's going to
find the comma and tell us at what point
in the string the comma is located that
way we can grab the stuff before and
after it ok now we're going to fetch the
Celsius temperature first off and store
that in temp C because remember temp C
is what gets drawn on the screen
and we'll do temp C equals data we're
going to use substring again so we don't
get that comma and so that we get the
part of it we want we're going to go
from zero to index and index is not
inclusive so if the comma is at five and
this is basically saying go zero to five
it's not going to include the comma so
we don't have to worry about doing minus
one or anything like that and then we're
going to fetch Fahrenheit comment it
temp F is going to equal data substring
this one is going to go from index plus
one right so we wanted to get the first
letter F the first number our letter
after the comma index plus one data
length and data dot length just returns
the last the last index okay and that
should do it
let's see if this makes a very pretty
temperature display all right look at
that very cool huh and I'll squeeze the
thing here and we should see the
temperature change yeah that's good and
remember you can change those colors by
changing those RGB values that I showed
you earlier and it'll update on the
screen and now you can use your Arduino
as a thermometer for your room if for
whatever reason you want to do that and
you can do all kinds of other great
stuff like this you could have it turn
on an alarm on your computer when it
gets up to a certain temperature you
could do all kinds of stuff in fact I
look forward to seeing what kind of
stuff you guys do with processing and
the Arduino thanks for watching this
episode of my Arduino tutorial series as
always if you have any questions please
feel free to ask me on youtube on my
blog drumming bum comm or an element 14
and if you want access to the source
code or schematic for this episode I
always make them available for download
on my blog there's links in the video
description below if you have any
questions about how to use processing
you should definitely head over to the
website that have a ton of examples that
you can use to work through how the
processing environment works if you're
getting just getting used to it in fact
I myself am no expert at processing and
I checked out their website quite a bit
to put together this tutorial today so
if you have any questions stop by there
or ask me and I can try to help you out
too I hope you guys enjoyed this episode
and I'll see you guys next week thanks
to element14 for helping me to sponsor
this video series they were kind enough
to provide a lot of them
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 the arduino 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