This article is a basic tutorial of EAGLE CAD software. EAGLE stands for Easily Applicable Graphical Layout Editor. EAGLE is rapidly becoming popular CAD/CAM software among professionals, students and hobbyists. EAGLE is an Electronic Design Automation (EDA) application for Windows. Linux and Mac operating systems. Using platform of 16/32/64 bit.
You have to download the free version of EAGLE CAD software from here https://www.autodesk.com/products/eagle/free-download
Now we will use PTH components and make 2-sided board.
Create New Project: First of all create a project. Go to start menu control panel then create new project.
File -> New-> Project
Rename the Project: The green circle next to the project name shows that the project is open. Click it to close the project if required.
Right-Click -> Rename
New Schematics: Now after renaming the project you can right click it again to create new schematics
Right Click over Project name -> New -> Schematics
The schematic window will appear.
The free version of EAGLE has limitation of single sheet per design. The board size is also limited to 100mm x 80mm.
Save: Select suitable name for your schematics and click to save in .sch format.
File -> Save as
EAGLE Component Libraries are open so it is easy to select your electronic component. The best practice is to first of all place / add all components from library to schematics. Next you wire up all components together. Another way is to place some parts then wire up then again some parts then wire up again thus completing the whole schematics.
If have finished the schematics and doing PCB layout and want to delete the component on board, then you have to delete that component from schematics first. The EAGLE CAD also gives the undo tool.
Edit -> Undo (Or simply Ctrl + Z). This will undo any changes made.
Under the Edit Menu on the left tool bar, this add tool appear. Click this and the following window will open.
When you select the part, it will be highlighted and start hovering with your mouse cursor. Left click once and drop the part on schematics. After placing the component/part, the add tool will think that you will place the same part on schematic again. To avoid this and exit add mode, simply press "ESC" key twice. Or you can choose other tool to exit from add tool.
Now we place a frame. The frame is red color border and bottom right box detailing the designer's name, date and project title.
Now save your schematics again by clicking this blue icon. Just after saving the file, your frame title will be updated automatically on the bottom right corner.
Add Power Ports:
The power inputs VCC and GND are added to the schematics on the top left portion. You can drag the component over the schematics by clicking this tool found on the left tool bar or directly under edit menu. To pick the part/component up left click once and then hover the mouse on + sign and then left click again to release the part on schematics where you want.
Placement of Microprocessor and Supporting Parts:
Place the processor in the middle of schematics and supporting electronics on the bottom right corner as shown in the diagram. You can also rotate the component by selecting one of the four options given in the orientation or rotation toolbar.
Placement of Connectors
Now we will place 8 pin connector for analog ports, (2x3) ICSP programming header and serial programming port (6 pin).
Connecting the Components:
At this stage we have all the components placed/added on the schematics. Now we will connect them or wire them up together according to our design.
We will use NET button instead of Wire button. The wire button is used to simply draw the line whereas the net button will actually create nodes and connection between the components and also draw a green color line.
The net tool is located on the left tool bar in the bottom. Click on it and hover upon the edge of the pin and left click once now a line (green color) will start to follow your cursor now click on the other edge of another pin or any node or net to make a connection between them.
As we can be seen, the thin red color line shows the “pins” of the connector and component. A small green dot represents a “node”
The green color line is interconnection/wire or “net”
In this way you complete all the connections and do wiring of the schematics. The finished schematics with wiring and components placed will look like this
Making NET Stubs:
Sometimes we see in schematics that two pins that needs to be connected are on the two ends of the schematics sheet. That is they are at far distance and the net route will be long enough to see ugly. In EAGLE, the problem is solved by making NET stubs.
Let us take connector JP2 in our example and make net stubs. We will make short wire connection on each six pins of JP2. Starting from GND pin edge click once and leaving few grids away left click once again. The short is created now press ESC button to exit wire mode. Now do this for all other five pins. The result will be like that shown on right. These green lines are actually nets with no name and labels.
NAME and LABEL Tools:
- 1- Now we will select NAME tool from left tool bar and click on GND net on top and a dialog box will open then we will give name to the net “GND”. EAGLE will show warning to connect this net to all other nets named GND. Click OK. (Same is the case for VCC)
- 2- After this we will select the LABEL Tool. This tool is used to add “text” to the net we just named. Click on label tool and then click the net, a text “GND” (same as the NAME) will appear as label. Left click and drop the label on top of the net.
- 3- Repeat NAME and LABEL for all 6 pins of JP2 to get look like this. (Please note that RX and TX are connected in cross connection)
Now we have to make other end of NET Stubs. The other end of DTR, RX and TX will be in micro-controller inputs.
The same steps from 1-3 will be followed but this time on the controller side. According to your design, where you want the net to be connected, connect the net stubs accordingly. The resultant will be like this
Note that there is no green line/wire/net present between these NET stubs. This is the advantage that the schematics looks clean and tidy while also connecting the desired pins according to design.
The same steps will be followed for programming port (2x3). The resultant for J2 programming port will look like this
Now make the other end of these net stubs of J2 on the micro-controller side. In the same way/steps as followed above. This will look like this
The schematics is done. The final schematics looks like this