Printable

This is a continuation of the previous Pad2Pad tutorial. In this lesson, we will continue with the Project 1 circuit board, learning how to use the Via tool, adjust the layers, and label the board.

At the end of the tutorial, there is a link to open a printable version of this tutorial.

If you have any suggestions on improving this or other tutorials, would like to see another added or even have one ready that you would like to add to the site, send the webmaster an email with the description and, if applicable, a copy of the tutorial you wish to submit.

Start by creating a net to connect the negative battery through hole connection to the top pad of C1 and label the net GND. Follow with connecting pin 3 (the large pad) of the voltage regulator, the top pad of C2, and pins 6, 18, 28, and 39 of the Atmega 16.

Figure 11.1

Create traces for the negative leads in the same manner as you did for the positive lead from the negative through hole connector to the top pad of C2.

Figure 11.2

Now we will go over how to cross over traces without causing a short. To do this, you will need to use the Via Tool button. The via tool drops through board via to connect traces from one side of the board to the other.

Figure 11.3

Click the Via Tool and drop two via on the board, one on each side of the 5vcc trace running from C2 to the Atmega microcontroller. Draw a trace from the top pad of C2 to the first via.

Figure 11.4

Now drop another via on the other side of the 5vcc trace. Connect the two via with a trace set to the bottom layer.

Figure 11.5

You now have crossed the 5vcc trace on the bottom of the board without shorting the circuit. Continue drawing the remaining traces to the GND pins of the Atmega 16 using the through hole via when you need to cross another trace.

Figure 11.6

Notice how I removed the second via from the right side of the 5vcc trace and added 4 via to the inside of the microcontroller. I also rearranged the 5vcc via inside the microcontroller to better accommodate the GND connections. You will have to make many adjustments when you are designing your project's board.

Now that we have traces on both sides of the board, the view can become pretty cluttered, making it difficult to determine if your traces on the bottom side of the board are overlapping or just look the way you intend. To see more clearly an element, click on View, then Layers. A window will open for you to adjust the colors of the individual layer components, such as the yellow top silk screen color or the red top trace color. To remove the view of the items cluttering the screen, just click on the check mark next to the item to remove it from view. When you want the items to return to view, simply reopen the screen and recheck the layers.

Figure 11.7

This is the view without the top layers cluttering the screen.

Figure 11.8

Connect the switches and switch resistors to the microcontroller in the same logical order that you had them connected on the prototype board. Start with switch one. The switches used in this example are normally open, momentary switches which means when left alone the circuit is open. When the button is pressed, the switch connects the pins from side A to side B. You cannot put two different circuits on one switch because both side A pins are a single circuit as is the same with side B.

Consulting the pin layout in the Atmega 16 data sheet, we see that PortB.2 through PortB.5 are pins 42, 43, 44, and pin 1 respectively. Draw a net from the Atmega pin 42 to the bottom pad of R3. Name that net portb2. Draw a separate net from the top pad of R3 to a B side pin on switch 1. Name that net switch1. Draw the final net for the switch 1 circuit from an A side pin to any ground. That net will already be named GND and will not ask you to rename it.

Figure 11.9

Now create your traces for the nets you dust drew.

Figure 11.10

Finish the switches, connecting switch 2 to pin 43, switch 3 to pin 44, and switch 4 to pin 1. Make sure you save your board often. If the software crashes, you will lose all of your work since your last save.

Figure 11.11

Next we will connect the LEDs. When connecting them, use the narrow end of the LED outline as the Cathode, or positive end. Start by drawing a net from pin 40 to the top pad of R1. Name that net portb0. Draw a separate net from the bottom pad of R1 to the square end pad of the LED. Name that net LED1. Draw the final net from the narrow end of the LED to pin 3 of the voltage regulator. That net will already be named.

Figure 11.12

Now connect the nets with traces. Do the same operations for LED2 from pin 41.

Figure 11.13

Identifying the board

Now we will identify the board. If it is an original board of your design, you will want to include a copyright statement on the drawing. Also, if you have submitted for a patent or provisional patent, you will want to post a 'PATENT PENDING' statement on the board. Use the Text Tool button and either the silk screen layer, the top trace layer, or the bottom trace layer to have your statement written on the board. Also, include a model number as your identifier for the board. If it is done with a trace layer, your board will be identified with copper beneath the mask. That is a more permanent identifying mark.

Figure 11.14

I used the bottom trace layer. There was more room for the statement on the bottom of the board. When viewing it from the software, the writing will be in reverse. It will print correctly on the boards you order.