Create library in CadSoft (Eagle) by using existing library

*** Thanks for Kevin Bolding ***

Copying a Symbol from another Library

The first step in copying a symbol is to open up the library that has the existing part.  Use File/Open to open the 74XX-US.lbr library.  Choose the Edit Symbol tool  and select the symbol 7400.  We are going to copy this into our library to make a new gate called the 999.  First, make sure all layers are visible by choosing the Layers button and selecting All.  Now, make the entire symbol into a group by using the Group tool  and drawing a rectangle around everything visible.  Finally, select the Cut tool  to and click on the group to copy the group onto the clipboard.

Now we can copy the symbol into our own library.  Open up your custom library.  Click on Edit Symbol  and enter “999” for the new symbol name.  Now, use the Paste tool  to paste a copy of the 7400 Nand gate into the new symbol.  You may now edit it as you like (for instance, change one of the input pins to be inverted by using the Change tool  to change the function from None to Dot.  Click one of the pins and it will change as shown below:

You may now save your symbol and use it as part of other devices.

Copying a Package  from another Library

Most common packages (such as the DIL8 we just made) already are defined in some library or another.  You’ll find it easiest to copy them rather than re-make them.  Copying packages is the same as copying symbols.  You might want to try copying the DIL8 package from the 74XX-US library into your new library.  (Of course, you won’t want to copy over your existing DIL8, so name the copy DIL8A.)

Ps: Select all layers before group select, and cut group then.

Putting Gates and Packages Together Into Devices

The final task in making a part is to create a device that has information on how symbols are placed inside of a package.  For many devices, there will be only one symbol.  However, many devices contain multiple symbols, as well as hidden power pins.  This is the case for the Gizmo device, which contains three Gizmogates and hidden power pins.

Make a new device by clicking on the Device button .  Enter “GIZMO” in the New field.  Now, add three copies of the Gizmo symbol, since the Gizmo device will contain three Gizmo gates.  Change the names of the three Gizmos to “A”, “B” and “C” by clicking the Names tool .

Since the Gizmo package will have Power and Ground pins, but the symbols don’t include the pins explicitly, we need to add a Power/Ground symbol to the device as well.  To save some time, we’ll copy thePWRN symbol from another library and use it instead of creating a new symbol.  Follow the directions for copying a symbol from another library above and copy the symbol PWRN from the library 74XX-US.lbr.  Give the new symbol the name PWRN in your library.  Now you can put the PWRN symbol in the Gizmo package by using the Add tool .  Give the symbol the name PWR by using the Name tool.

Since there are multiple symbols in this package, we need to specify how they are added to a schematic.  Normally, we just add the next symbol as needed.  In other words, the first symbol is Gizmogate A, then Gizmogate B, and so on.  To specify this, change the Add level to “Next” by using the Change tool  and selecting AddLevel Next.  Click on the three Gizmogates to change their Add levels to Next. The PWRN symbol usually is hidden on a schematic, so we don’t want to add it like we add the Gizmogates.  Change its Add level to Request to indicate that it will only be added if specifically requested by the designer.  It will still be in the gate, but it won’t appear on the schematic.

The final step in making a device is to specify a package and the connections from symbol pins to package pads.  First, we’ll want to specify the package we just designed, the DIL8.  Click on the NEW button at the bottom of the screen under the package variant window. Select your new package, the DIL8.  You may also want to assign a prefix of “GZ” to the symbols in this package - that way the first symbol you add will be GZ1, the next GZ2, and so on.  Use the Prefix button to change the prefix.

Now we can complete the device by assigning symbol pins to package pads.  Click on the Connect button  and a window will pop up to allow you to connect pins to pads.  Since there are three Gizmogates, you’ll see three sets of IN and OUTB pins for gates A, B, and C.  There are also the GND and VCC pins as well.  Start by connecting A.IN to pad P$1 by selecting both and pressing Connect. Connect the remaining pins to pads as follows:


Your final device should look like the following diagram: 

We’re finally done with the device.  Save it!