6. Electronics Design¶

Individual Assignment¶

Use an EDA tool to design a development board that uses parts from the inventory to interact and communicate with an embedded microcontroller

Software¶

I decided to use KiCad to design my PCB because I have some prior experience using KiCad. KiCad has a Schematic Editor and a PCB Editor. In the schematic editor, you have to add all the components you want in your PCB and connect them, but it does not matter what the connections look like. In the PCB Editor, you lay out all the components exactly how you want it to be made, and the connections are already made from the Schematic Editor. I wanted to start out by making a simple PCB that could make an LED blink using a button using surface-mount components since that is what I did in the Embedded Programming, and I felt pretty confident making this circuit.

Typically, to design a PCB in KiCad, you start out by designing the schematic in the Schematic Editor. To do that, you have to press the Symbol Library browser and select all the components you want in yout design.

Then, you need to draw all the connections in the Schematic Editor and ensure each component has the correct footprint.

Next, you need to go to the PCB Editor and press Update PCB from Schematic to get the component footprints to appear.

You have to organize and draw the traces of the PCB exactly how you want it to look on the copper. I did all my traces in the F. Cu. layer. Then, when it is all organized, you need to go to the Edge Cuts layer and draw the outline of the PCB. Last but not least, you need to export the design. To do this, I selected Fabrication Outputs and exported the F. Cu. and Edge Cuts layers as Gerber files.

This is what the entrance screen looks like in KiCad right after creating a new project:

Schematic Editor¶

First, I needed to add the Fablab library to the Schematic Editor, so I would have the right components that my school lab has. I followed this tutorial to learn how to do this.

Initially, I considered using an ATTiny412 since I wanted to make such a simple design, and the ATTiny would be fully capable of making an LED blink using a button.

I ended up changing my time because I wanted to continue exploring the Xiao RP2040 since that is most likely the microcontroller I will use for my final project, and I wanted to practice making a PCB with it. Every time I added a component I needed to ensure that it had the correct footprint assigned to it. Most of them defaulted to the correct footprint, but it was important to double check. I learned the hard way that if a component does not have a footprint or does not have the correct footprint, it will appear incorrectly in the PCB Editor or will not appear at all.

This is the footprint I used for the RP2040:

This is a screenshot of me designing the schematic:

This is the final schematic:

I did not know exactly which components to choose because there were several options for things like resistors, so i looked at Angelina Yang’s Fab Documentation to see which ones she used. I started out following her documentation, but then, I decided it would be easier just to figure it out myself.

PCB Editor¶

Next, I navigated over to the PCB Editor. First, I had to make sure I had the Fab library, which I did because I did that first. Then, I had to press the Update PCB from Schematic button to make the components I added in the Schematic Editor appear. After that, since the connections already existed, I just had to add the PCB traces. I made sure I was on the correct layer, which was F. Cu since I wanted front cuts and then used the trace tool to connect the components the way I wanted. It is very important that there are NO RIGHT ANGLES because current does not flow well in right angled traces. Also, it is important that no traces overlap unless you mean for them to because that can cause issues when using the PCB. I also had to change the size of the traces to 0.75 mm I believe.

To make the outline of the PCB, I then went to the Edge Cuts layer. I just wanted a simple rectangle-shaped PCB, so I used the rectangle tool to make a box around the components. I found it helpful to do this step last because typically, you want the outline to be as close to the components as possible in order to save copper.

This is a screenshot of my final PCB design in the PCB Editor:

3D Viewer¶

There is also an option to view the PCB design in the 3D Viewer, which is very helpful because it gives a rough idea of what the final product might look like. This tool was also helpful when picking components because you can see what the components look like.

This is a screenshot of my final PCB design in the 3D Viewer:

Exporting the Design¶

The last thing I needed to do in KiCad was export the design. This step is very important to do correctly because you have to make sure to export the correct layers.

This is a screenshot of the settings I used when exporting my PCB design from KiCad:

Since all the components of my design were surface mount, I did not need to export the through hole file, which I have done in the past when designing through hole PCBs.

This is what the gbr file for the front cuts (FCu) looks like:

Final PCB¶

This is my milled and soldered PCB working correctly:

To see my milling and soldering process, you can visit my Electronics production page.

Group Assignment¶

Our group assignment for this week was to use the test equipment in our lab to observe the operation of a microcontroller circuit board using, as a minimum, a multimeter and oscilloscope and then document our work. My partner for this week was Zaina Gibrine, and we worked pretty well together. We worked together on all parts of this group project and just divided up the documentation. I documented the multimeter and logic analyzer sections. Here is a link to the full group documentation for this week.

Multimeter¶

First, we tried performing several tests with a multimeter. We asked ChatGPT for some examples of tests we could perform and ended up just choosing two.

This is the blink code we used:

#define LED_PIN 0  // D0

void setup() {
  pinMode(LED_PIN, OUTPUT);
}

void loop() {
  // Gradually dim the LED
  for (int brightness = 255; brightness >= 0; brightness--) {
    analogWrite(LED_PIN, brightness);
    delay(10); // Adjust speed of fading
  }

  delay(500); // Wait before repeating
}

This is a video of the circuit blinking:

Test GPIO Pin Outputs¶

This is the test ChatGPT recommended we perform:

We followed ChatGPT’s instructions and used the simple Arduino blink code to blink the LED.

Test Power Supply¶

This is the test ChatGPT recommended we perform:

To know which multimeter setting to use, we found this image on Google:

This was probably my favorite test we tried to conduct. It was really cool to see how the 3.3 and 5 Voltage pins on the microcontroller showed up on the multimeter.

To know which multimeter setting to use, we found this image on Google:

This is an image of us testing the 3.3V pin:

This is an image of us testing the 5V pin:

We attempted to do a few other tests, but these tests were probably the most helpful and the most useful when making circuits later on, especially if we solder the board ourselves. When soldering, it can be easy to create a tiny solder bridge or other soldering mistake, and using a multimeter, you can find where the mistake is.

Oscilloscope¶

Zaina wrote this part of the group documentation.

What is an Oscilloscope?¶

An Oscilloscope is an electronic test instrument that allows you to visualize and analyze electrical signals in real time. It displays voltage as a function of time on a screen, typically using a graph with the x-axis representing time and the y-axis representing voltage.

What are Oscilloscopes used for?¶

Troubleshooting circuits in electronics and electrical engineering. Measuring signal properties like amplitude, frequency, and phase. Observing waveforms from components like sensors, transistors, and microcontrollers. Testing and debugging communication signals

What was Observed?¶

Garrett Nelson helped us set this tool up. The LED is turned on and off at regular intervals, creating a waveform alternating between high, 3v3 or 5v, and low, 0v. This creates a square pattern on the oscilloscope.

We tested 2 different frequencies on our LED to observe on the Oscilloscope. The waves were square, had a long period, and the pulses were widely spaced. To the human eye, the LED always appeared to be on. However, it was densely packed square wave with very short transitions.

We also made a fade code that made the LED fade using ChatGPT:

Here are two videos and a picture of us using the oscilloscope:

Logic Analyzer¶

We also used a logic analyzer this week. A logic analyzer is an electronic instrument used to capture and analyze digital signals in a circuit. It monitors multiple channels at the same time, displaying signal timing and logic states to help find communication errors, timing issues, and protocol violations. Unlike an oscilloscope, which measures analog waveforms, a logic analyzer focuses on digital signals, interpreting high and low states over time. Logic analyzers are also very useful when testing circuits and debugging because they can help find your issue quickly when used with the correct settings (ChatGPT and I collaborated on that description).

Here is a video of us testing our simple blink circuit with the logic analyzer:

Reflection¶

This week was not too difficult because I have used KiCad before. I later went on to mill this board and was happily surprised that it worked first try! To see my milling process, you can visit my Electronics production page. I enjoyed the group portion of the project this week because, although it was not the most exciting, I learned a lot about testing electronics, which I think will come in handy when I am working on my final project. I have worked with multimeters before, and they are very helpful with testing electronics because they can be used to find the errors in circuits, whether it is a burnt out LED or a wire that does not work. I will definitely be using a multimeter again, and I will definitely use KiCad to design the PCB for my final project.