Build Your Own Arduino
Project #1 Circuit Design
With a few inexpensive parts and a solderless breadboard you can
quickly and easily build your own Arduino. This concept works great
when you want to prototype a new design idea, or you don’t want to tear
apart your design each time you need your
Arduino.
The example below shows how to hook up the components on your
breadboard. We will go into further detail throughout this project.
Figure 1-1: Breadboard Arduino with USB programming ability.
Before we get started, make sure you have all the necessary items in the component list box.
If you need to purchase parts you can do so from my site at www.ArduinoFun.com or in the back of this book is a listing of several sites that sell Arduino related items.
* See note about the TTL-232R
cable in programming options before
purchasing.
Build Your Own Arduino
Project #1 Step by Step
The first thing you need to do is set up power. With your breadboard and
components in front of you… let’s get started!
With this step, you will be setting the breadboard Arduino up for constant
+5Volts power using a 7805 voltage regulator.
Figure 1-2: Power setup with LED indicator.
In order for the voltage regulator to work, you need to provide more than
5V power. A typical 9V battery with a snap connector would work just
fine for this.
Power is going to come into the breadboard where you see the red and
black + and – squares. Then add one of the 10uF capacitors. The longer
leg is the Anode (Positive) and the shorter leg is the Cathode (Negative).
Most capacitors are also marked with a stripe down the negative side.
Across the empty space on the breadboard (the channel) you will need to
place two hook-up wires for positive (red) and ground (black) to jump
power from one side of the breadboard to the other.
Now add the 7805 voltage regulator. The 7805 has three legs. If you are
looking at it from the front, the left leg is for voltage in (Vin) the middle leg
is for ground (GND) and the third leg is for voltage out (Vout). Make sure
the left leg is lined up with your positive power in, and the second pin to
ground.
Coming out of the voltage regulator and going to the power rail on the
side of the breadboard you need to add a GND wire to the ground rail and
then the Vout wire (3rd leg of the voltage regulator) to the positive rail.
Add the second 10uF capacitor to the power rail. Paying attention to the
Positive and Negative sides.
It’s a good idea to include an LED status indicator which can be used for
troubleshooting. To do this you need to connect the right side power rail
with the left power rail. Add positive to positive and negative to negative
wires at the bottom of your breadboard.
Figure 1-3: Left and Right Power Rail Connections.
Having power on the left and right power rail will also help to keep your
breadboard organized when providing power to the various components.
Figure 1-4: For the LED status indicator, connect
a 220Ω resistor (colored as: red, red, brown)
from power to the anode of the LED (positive
side, longer leg) and then a GND wire to the
cathode side.
Congratulations, now your breadboard is set up for +5V power. You can
move onto the next step in the circuit design.
Now we want to prepare the ATmega168 or 328 chip. Before we begin,
let’s take a look at what each pin on the chip does in relationship to the
Arduino functions. NOTE: The ATmega328 runs pretty much the same
speed, with same pinout, but features more than twice the flash memory
(30k vs 14k) and twice the EEPROM (1Kb vs 512b).
Figure 1-5: Arduino Pin Mapping
The ATmega168 chip is created by Atmel. If you look up the datasheet
you won’t find that the above references are the same. This is because
the Arduino has its own functions for these pins, and I have provided
them only on this illustration. If you would like to compare or need to
know the actual references for the chip, you can download a copy of the
datasheet at www.atmel.com. Now that you know the layout of the pins,
we can start hooking up the rest of the components.
To start, we will build the supporting circuitry for one side of the chip and
then move on to the other side. Pin one on most chips has an identifier
marker. Looking at the ATmega168 or 328 you will notice a u-shaped
notch at the top as well as a small dot. The small dot indicates that this is
pin 1.
Figure 1-6: Supporting circuitry pins 15-28
From the GND power bus, add a jumper wire to pin 22. Next, from the
positive power bus, add jumper wires to pin 20 (AVCC - Supply voltage
for the ADC converter. Needs to be connected to power if ADC isn't being
used and to power via a low-pass filter if it is (a low pass filter is a circuit
that cleans out noise from the power source, we aren't using one)
Then add a jumper wire from the positive bus to pin 21 (Analog reference
pin for ADC).
On the Arduino, pin 13 is the LED pin. Note that on the actual chip the
pin is number 19. When uploading your sketch code and for all projects
you will still reference this as Pin 13.
To hook up the LED, add a 220Ω resistor from GND to the cathode of the
LED. Then from the anode of the LED add a jumper wire to pin 19.
Now we can move onto the other side of the chip. You are almost
finished!
Figure 1-6: Supporting circuitry pins 1-14
Above the ATmega168 chip near the pin 1 identifier, place the small tact
switch. This switch is used for resetting the Arduino. Right before you
upload a new sketch to the chip you will want to press this once. Now
add a small jumper wire from pin 1 to the bottom leg of the switch then
add the 10K resistor from power to the pin 1 row on the breadboard.
Finally add a GND jumper wire to the top leg of the switch.
Add power and GND jumpers to pin 7(VCC) and pin 8 (GND). Add the
16MHz clock crystal to pin 9 and 10 and then the two .22pF capacitors
from pins 9 and 10 to GND. (See note below for alternative method).
Your basic breadboard arduino is now complete. You could stop right
here if you wanted to and swap an already programmed chip from your
Arduino board to the breadboard, but since you came this far, you might
as well finish off by adding some programming pins. This will allow you to
program the chip from the breadboard.
NOTE: Instead of using the 16MHz clock crystal, you can use a 16 MHz
ceramic resonator with built-in capacitors, three-terminal SIP package.
You will have to arrange your breadboard a little differently, the resonator
has three legs. The middle leg will go to ground and the other two legs
will go to pins 9 & 10 on the ATmega168 chip.
Referring to Figure 1-6, locate a spot where you have 6 columns on the
breadboard that are not in contact with anything else. Place a row of six
male header pins here.
With the breadboard facing you, the connections are as follows:
GND, NC, 5V, TX, RX, NC, I am also calling these pins 1,2,3,4,5,6. From
your power bus rail, add the GND wire to pin 1 and a wire from power for
pin 3. NC means not connected, but you can connect these to GND if
you want to.
From pin 2 on the ATmega168 chip, which is the Arduino RX pin, you will
connect a wire to pin 4 (TX) of your programming headers. On the
ATmega168 chip, pin 3 Arduino TX gets connected to pin 5 (RX) on your
header pins.
The communication looks like this: ATmega168 RX to Header Pin TX,
and ATmega168 TX to Header Pin RX.
Now you can program your breadboard Arduino.
Programming Options
The first option is to buy a TTL-232R 3.3V USB – TTL Level Serial Cable.
These can be purchased at www.adafruit.com or www.ftdichip.com
The other two options, which I prefer are to buy one of two breakout
boards from SparkFun.com. They are:
FT232RL USB to Serial Breakout Board, SKU: BOB-0071 (This
option takes up more space on your breadboard)
FTDI Basic Breakout - 3.3V SKU: DEV-08772 (This option, and
using right angle male headers works the best out of all three
because it is secured better on the breadboard)
Build Your Own Arduino
Project #1 Programming the ATmega168 chip
Double check your connections, make sure your 9V battery is not
connected and hook up your programming option. Open up the Arduino
IDE and in the Example sketch files, under Digital, load the Blink sketch.
Under the file option Serial Port, select the COM port that you are using
with your USB cable. i.e. COM1, COM9, etc.
Under the file option Tools/Board, select either:
Arduino Duemilanove w/ATmega328
Arduino Decimila, Duemilanove or Nano w/ATmega128
(depending on which chip you are using with your breadboard Arduino)
Now press the upload icon and then hit the reset button on your
breadboard. If you are using one of the SparkFun breakout boards, you
will see the RX and TX lights blink. This lets you know that the data is
being sent. Sometimes you need to wait a few seconds after pressing the
upload button before pressing the reset switch. If you have trouble, just
experiment a little with how fast you go between the two.
This sketch if uploaded properly will blink the LED on pin 13 on for one
second, off for one second, on for one second… until you either upload a
new sketch or turn off the power.
Once you have uploaded the code, you can disconnect the programming
board and use your 9V battery for power.
Troubleshooting
No Power – Make sure your source power is above 5V.
Power but nothing works – recheck all your connection points.
Uploading error – Refer to www.arduino.cc and do a search on the
particular error message you receive. Also check the forums as
there is a lot of great help there.
1 Cup Grapes
