Eagle Schematic Design Software
This is a short tutorial on using the Eagle Layout Editor from CadSoft, version 7.1.0, for
schematic entry. This software is used for entering schematic diagrams and designing printed
circuit boards (PCBs). You can download it from: http://www.cadsoftusa.com/downloadeagle/?language=en . The first time you start EAGLE, you will be asked whether you have a
personalized license disk, or whether you want to run EAGLE as Freeware. To use the Freeware
license select the “Run as freeware” button.
There are written tutorials online1; however, I found it more helpful to watch some video
tutorials. Here is a good video tutorial that covers the user interface, and shows how to draw a
schematic: https://www.youtube.com/watch?v=1AXwjZoyNno.
Creating a Schematic
Start Eagle; this will bring up the “Control Panel” window shown in Figure 1.
Figure 1 Main “Control Panel” window.
To create a schematic, select New-> Schematic. This brings up the window shown in Figure
2. We can now start inserting parts from the part libraries that are stored in Eagle’s library
directory. On my computer, this is in C:\EAGLE-7.1.0\lbr. Note that if there are folders
in that directory, it doesn’t look inside the folders (i.e., it just finds all the “*.lbr” files at the top
level).
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See http://www.cadsoft.de/wp-content/uploads/2011/05/V6_tutorial_en.pdf.
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Although there are a very large number of
parts in the directory, you may still find that
the part you need is not in the directory. You
can look to see if the manufacturer has an
Eagle library you can download; if not, you
can create your own Eagle part (described in
the next section).
To add a part, click on the “add part” icon,
which looks like this (
) or select Edit>Add. This will bring up a window showing
all the libraries that are available.
Let’s add some discrete components to our
diagram. In the search box, type “resistor”
and hit enter. This will show all parts that
have “resistor” in their name or description.
Figure 2 Schematic Entry.
In the list of parts, pick the library called “resistor” and the device called “R-US”. This will
show a bunch of variants of that device, each with a different physical package. For example,
the one selected in Figure 3 is a package that fits 2.5 mm holes.
Figure 3 Adding a resistor.
Since we are just interested in drawing a schematic diagram, we don’t really care about which
package is used, so any of these are ok. All we care about is the symbol that will appear on our
schematic diagram. Of course, if you are ultimately going to design a PCB, you do need to
select the device with the correct package type.
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Click “OK” on the window. The window will disappear and you can add the part to the
schematic diagram by clicking on the diagram. Click on the “STOP” button (
the screen to get out of the “add-a-part”
mode.
) at the top of
Now add some additional parts to the
diagram. Search for “gnd” and add that
symbol to the diagram (it doesn’t matter
which one you pick). Search for “LED” and
add an LED symbol. Many options will be
available; just pick one for which you like
the symbol. I used the device called
“LED_E” in the library “eagle-ltspice”. The
window should look something like Figure 4
(you may have to zoom in ... see the “View”
menu).
Figure 4 Schematic diagram so far.
The delete button (
) at the left side of the
screen is useful if you want to delete a part you have added. Again, to get out of that mode, hit
the STOP button. If you want to move your symbols around, hit the “Move” button (
) at the
left side of the screen. Then click on the part you want to move and move it to the new place.
Again, to get out of that mode, hit the STOP button. To rotate a part that has already been
placed, select the “Rotate” button (
another 90 degrees.
). Then click on the part to rotate it. Each click rotates
Now let’s add the symbol for our microcontroller. Recall that the microcontroller chip is on the
little daughter board (the “Nanocore” module) that plugs into the SSMI board, and the pins come
out to header H1 on the SSMI board. Instead of drawing the symbol for the microcontroller
chip, and all the circuitry on the daughterboard, we will just draw the interface to the Nanocore.
Any circuitry you develop in labs or for final projects will simply interface to the Nanocore.
We have created a symbol for the Nanocore module, which is in a library called
“EENG383.lbr”. Download this library from the course website. To tell Eagle to use this
library, select “Library->Use” from the menu at the top of the schematic entry window.
Then browse to wherever you have saved the library file, and select it.
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Select the “add a part” button again and find the “EEGN383” library from the list of libraries.
Find the device in that library called “NANOCORE”. Add that device to the schematic.
Now we want to wire up the connections to our parts.
Select the button for “Draw an electrical connection” (
) from the left side. Click once on the starting point
of the wire, and once on the ending point. Note that
you can draw a bus with a thick line using the
button. Make the connections shown in Figure 5.
We can (and should) add values for parts such as
resistors and capacitors. To do this, click on the button
for “Define the value of an object” ( ) on the left side
of the screen. Click once on the resistor. This will
bring up a pop-up window, in which you can type the
value, such as “1K”. Finally, you can add other text
labels (e.g., signal names) using the text button (
Figure 5 Final schematic. (Note – to
“move” the Nanocore symbol, you have to
click on the little “+” to the right of the
symbol, where the arrow is pointing.)
).
To include your schematic into a lab report, you can simply capture the screen (on a Windows
computer, this is the key combination ALT-PRINTSCREEN). Then paste the image into a
Microsoft Word document. You can crop the image after pasting it in, to hide the window
borders. In Word, you right click on the image and select the “crop” button, which looks like
this (
).
Creating a Part
If you need a part that is not in the library, you can always just draw it in the schematic entry
window, using the “Line” tool (
). However, it is almost as easy to create a part that can be
put into a library. This has the advantage of being able to reuse it; also it is much easier to move
it around.
To make a part, you have to define the “symbol” (which goes on the schematic diagram) and a
corresponding “package” (which specifies the physical size and layout, for the PCB). These two
are linked into a “device”.
If you want additional detail beyond this introduction, these tutorials are helpful:
 http://www.youtube.com/watch?v=RIfX3fxSpNY (Part 1, shows how to make the package)
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
http://www.youtube.com/watch?v=1z9yUyguSzA (Part 2, shows how to make the symbol)
Go back to the main “Control Panel” window and select “File->New->Library”. This
should bring up an empty library window as shown in Figure 6.
Figure 6 Library window.
Select the “Symbol” button at the top of the screen, which looks like this (
). This will bring
up another window as shown in Figure 7. Type the name of your symbol in the box. For this
tutorial, we will make a simple 3-pin part called “GP2D120”. Then click “OK”.
Figure 7 Edit window.
After clicking “OK” on the “Edit Window”, it should bring up the symbol editor window. Click
on the “Draw a pin” button on the left side, which looks like this (
screen. The result should look like Figure 8.
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). Place three pins on the
Figure 8 Symbol editor.
Select the “rotate” tool (refer to the previous section if necessary to see how to do this) and rotate
the rightmost pin 180 degrees. Move the pins if necessary to space them apart. Next, draw an
outline of the package using the “draw a line” tool (
like Figure 9.
). The result should look like something
Figure 9 Partially completed part.
Click on the “Name” button on the left (
). Click on each of the pins in turn, and rename
them, to “VCC”, “GND”, and “VOUT”, respectively.
Click on the “Text” button on the left ( ). This will bring up a window for you to type in a text
string. Type “>NAME” and click “OK”. Before placing the string onto the diagram, go to the
top of the Symbol editor window and change the layer from “Symbols” to “Names” (see Figure
10). Then place the string above or below the part. Select the “STOP” button to get out of this
mode.
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Figure 10 Selecting the "Names" layer.
Select the “Text” button again and this type create a string called “>VALUE”. Before placing
the string onto the diagram, change the layer to “Values”. Then place the string above or below
the part symbol. The final completed symbol is shown in Figure 11.
Figure 11 Final completed symbol.
This is a good time to save your work. Save the library in a location for which you have write
privileges.
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Now create a package. If you really intended to design a PCB, you would be very careful about
specifying the correct dimensions and outline for the part. However, since we are just interested
in the schematic, we don’t care about those things. The only thing we need to do is to create a
dummy package with the same number of “pads” as we have “pins” on the symbol.
On the library window, select the “Package” button at the top of the screen (
). Type a name
for the package (you can use the same name as for the symbol) and click “OK”. This will bring
up the package editor window. Select the “Draw a pad” button (
) at the left, and place three
pads on the screen. It doesn’t matter where they go. The result should look something like
Figure 12.
The default pin numbers will be
“P$1”, “P$2”, etc. To change
them to “1”, “2”, etc., do the
following. Click on the “Name”
button on the left ( ) and then
click on a pad. Change the name
to “1”. Repeat for the other two.
Save the library. Now select the
“Device” button (
) at the top
of the screen. This will bring up
a popup window, where you
Figure 12 Package editor.
enter “GP2D120” again for the
name. Then it will bring up a
device editor window, as shown in Figure 13. On the left side of the window, select the
“Symbol” button. Choose the symbol that you created above, and place the symbol onto the
screen. Next, click on the “New” button in the lower right corner of the screen, and click “OK”
on the popup window. The result should look something like Figure 13.
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Figure 13 Device editor window.
Finally, click on “Connect” at the lower right corner of the window. This will bring up a
window as shown in Figure 14. Click on “Connect” three times. This will tell Eagle to connect
the three pins from your symbol to the three pads on your package.
Figure 14 Connection window.
Click “OK” to exit this window. Save the library and exit the library window. You can now use
your device in your schematics!
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