Group Assignment

This week focused on hands-on use of professional lab equipment to analyze, debug, and understand real microcontroller-based circuits. The goal was to measure electrical parameters, visualize signals, and interpret communication between devices using industry-standard tools.

You can access the group assignment here.

Lab Equipment Used

Digital Multimeter

Used to measure voltage, current, resistance, frequency, and continuity. It was essential for verifying PCB traces, checking 5V and 3.3V power rails, testing components, and detecting short circuits before powering boards.

Digital Oscilloscope

Used to visualize real-time waveforms and analyze signal behavior. We measured frequency, amplitude, duty cycle, and waveform shape. It helped us understand PWM signals, timing behavior, and signal stability.

Logic Analyzer

Used to capture and decode digital communication protocols such as UART and I²C. It allowed us to observe real data transmission, analyze timing relationships, and decode serial communication automatically.

Function Generator

Used to generate controlled sine, square, and triangle waveforms across different frequencies and amplitudes. It was tested using a piezoelectric crystal to observe vibration and sound generation at various frequencies.

Programmable Bench Power Supply

Provided regulated DC power with adjustable voltage and current limiting. It was used to safely power microcontroller boards, measure current consumption, and protect circuits from overcurrent damage.

Practical Experiments

We used a Seeed Studio XIAO RP2040 to generate PWM-based waveforms such as sine, square, triangle, sawtooth, ramp, and pulse. The oscilloscope was used to visualize and verify the signals, while the logic analyzer decoded UART and I²C communication from the board.

History of Electronics

Introduction

Electronics is the science and technology of controlling electric current to do useful tasks. This includes things like amplifying sound, switching signals, processing information, and controlling machines. Modern electronics is everywhere — in phones, computers, cars, and even household appliances. But it wasn’t always this small and powerful. Let’s start from the beginning.

1. Early Electronics: Vacuum Tubes

In the early 1900s, the main electronic devices were vacuum tubes. These are glass tubes with electrodes inside that can control the flow of electricity. They could:

• Amplify weak signals (make radios louder)
• Act as switches to control electricity

Image taken from : Vacuum Tube

Vacuum tubes made early radios, televisions, and the first computers possible. But they had big problems:

• Very large and heavy
• Generated a lot of heat
• Broke easily and used a lot of power

Because of these issues, engineers wanted a smaller, more reliable alternative.

2. The Birth of the Transistor

In 1947, scientists at Bell Labs invented the transistor. A transistor is a tiny device that can:

• Amplify signals, just like vacuum tubes
• Act as a switch to turn electricity on or off

Image taken from : Transistor

Transistors are made of semiconductors, usually silicon. They are:

• Much smaller than vacuum tubes
• More reliable and energy-efficient
• Cheaper to produce

Transistors completely changed electronics. Radios, computers, and many other devices became smaller, faster, and more practical. Today, billions of transistors fit on a single tiny chip.

3. Integrated Circuits (ICs)

By the 1960s, engineers realized that connecting lots of transistors together on a circuit board was still bulky and complicated. The solution was the Integrated Circuit (IC):

• Many transistors, resistors, and capacitors built on a single small silicon chip
• Made electronics smaller, faster, and cheaper

Image taken from : Integrated Circuit | IC Definition, Types & Advantages

ICs are used in almost every electronic device today. For example:

• Microchips in computers and smartphones
• Embedded controllers in washing machines or cars
• Memory chips for storing data

Thanks to ICs, devices that once filled entire rooms could now fit in your pocket.

Embedded Microcontroller Simulation

Embedded microcontroller simulation is the process of testing and running a microcontroller-based system in a virtual environment before building the physical hardware. It allows designers to verify circuit connections, program behavior, and overall system functionality without using real components.

Wokwi

The objective of this task was to simulate and test a microcontroller circuit using an online simulator before building it on physical hardware. Instead of directly connecting components on a real board, I first verified the circuit design and program behavior in a virtual environment to reduce errors and avoid damaging components.

For this purpose, I used the Wokwi Online Simulator.

Creating a New Project

Next, I created a new project in the simulator. I first clicked on the Profile section and navigated to My Projects. From there, I selected the New Project option to start a fresh design. I then chose the Raspberry Pi Pico board from the available hardware options and selected Arduino as the programming environment. This set up a new workspace with the required board and code editor ready for development.

Understanding the Setup

After creating the project, the simulator automatically generated:

• A Raspberry Pi Pico board
• A default Arduino sketch file
• A simulation environment with wiring view

Writing the Code

I modified the default Arduino code to test basic functionality such as blinking an LED.

            void setup() {
                pinMode(5, OUTPUT); // Built-in LED pin for Raspberry Pi Pico
            }

            void loop() {
                digitalWrite(5, HIGH);
                delay(1000);
                digitalWrite(5, LOW);
                delay(1000);
            }
            

I clicked the Start Simulation button. The built-in LED connected to GPIO 5 started blinking, confirming that the code was working correctly.

Observation

The simulation successfully demonstrated the basic operation of the Raspberry Pi Pico using Arduino code. The LED blinked at a 1000 ms interval, confirming correct pin configuration and program execution.

Learning Outcome

• Understood how to create a new microcontroller project in Wokwi.
• Learned how to simulate Raspberry Pi Pico using Arduino framework.
• Verified code functionality before physical implementation.
• Understood GPIO pin control and timing using delay().

Conclusion

Using Wokwi allowed me to safely test and debug my microcontroller code without requiring physical hardware. This helps reduce errors before implementing the design in a real embedded system.

Pushbutton with OLED

Objective

To interface a pushbutton and an OLED display with a Raspberry Pi Pico and display different messages on the screen depending on the button state.

Components Used

• Raspberry Pi Pico
• Pushbutton
• SSD1306 128x64 I2C OLED display
• Connecting wires
• Wokwi simulator

Working Principle

The pushbutton is configured as a digital input using the INPUT_PULLUP mode. In this configuration:

• The input pin remains HIGH by default.
• When the button is pressed, the pin connects to GND.
• The pin then reads LOW.

The OLED display communicates with the Raspberry Pi Pico using the I2C communication protocol. The program continuously reads the button state. If the button is pressed, a specific message is displayed on the OLED. If the button is not pressed, a different message is displayed.

Circuit Connections

Pushbutton Connections

One terminal of the pushbutton is connected to GPIO 2.
The other terminal is connected to GND.
No external resistor is required because the internal pull-up resistor is enabled in the program.

OLED Display Connections (I2C)

Program Code

            #include <Arduino.h>
            #include <U8g2lib.h>
            #include <Wire.h>

            U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE);

            const int buttonPin = 2;

            void setup() {
                pinMode(buttonPin, INPUT_PULLUP);
                u8g2.begin();
            }

            void loop() {
                int buttonState = digitalRead(buttonPin);

                u8g2.clearBuffer();
                u8g2.setFont(u8g2_font_ncenB08_tr);

                if (buttonState == LOW) {
                    u8g2.drawStr(0, 30, "Button Pressed!");
                } 
                else {
                    u8g2.drawStr(0, 30, "Press the Button");
                }

                u8g2.sendBuffer();
                }
            

Code Explanation

In the setup function, the button pin is configured as INPUT_PULLUP and the OLED display is initialized using the U8g2 library.

In the loop function, the program reads the button state. The display buffer is cleared before writing new content. If the button is pressed (LOW), the display shows "Button Pressed!". If the button is not pressed (HIGH), the display shows "Press the Button". The buffer is then sent to the display.

Expected Result

When the button is not pressed, the OLED displays:
Press the Button

When the button is pressed, the OLED displays:
Button Pressed!

Electronic Design

KiCad

KiCad is a free and open-source Electronic Design Automation (EDA) software suite used for designing electronic schematics and printed circuit boards (PCBs).

The software includes several integrated tools, such as:

Create a New Project

1. Click File in the top left corner.
2. Select New Project.
3. Choose the folder where you want to save your project.
4. Enter your project name.
5. Click Save.

When a new project is created in KiCad, the software automatically generates several important files. Each file serves a specific purpose in the design process.

Kicad Project Manager

The KiCad Project Manager is the main control window that appears when you open a KiCad project. It acts as the central hub for managing all files and tools related to a specific electronic design project.

In the Project Manager window, locate the Schematic Editor icon, and click it to open the Schematic Editor.

Schematic Editor (Eeschema)

To begin designing the circuit, the Schematic Editor must be opened from the KiCad Project Manager.

When you open Eeschema, a new window appears with a blank schematic sheet. You will see options such as Add Components, Place Wire, Net Label, and other tools.

Add Components

1. Press A on your keyboard.
2. Or click the Add Symbol icon in the right toolbar.

A window called Choose Symbol will open. On the left side, you will see different libraries. On the right side, you will see the available components (symbols) from the selected library.

Use the search bar at the top of the Choose Symbol window.

You can further filter the results by using keywords or by selecting a specific library name.

• Type the component name:
  • R → Resistor
  • C → Capacitor
  • D → Diode
  • LED → Light Emitting Diode
  • GND → Ground
  • Microcontroller name (example: ATtiny, STM32, etc.)
• You can filter by keyword or library name.

Click on a symbol to see its preview. Check the pin count, pin names, and symbol type to ensure it matches your requirement. After verifying the details, click OK to select the symbol.

Move your cursor to the schematic sheet and left click to place the component. You can place multiple copies by clicking again at different locations. Press Esc to stop placing the component.

We decided to recreate the ATtiny412 Blink board from the Embedded Programming week, made by Neil. Working from that reference schematic, I recreated the circuit in KiCad using components sourced from the Fab library.

ATtiny Datasheet

KiCad Library Management

To streamline the design process and ensure access to common mechanical and electrical components, I utilized the KiCad Plugin and Content Manager.

Installing KiCad FabLib

Make sure you have KiCad 8 or later installed before proceeding with the installation.

KiCad FabLib on GitHub

Go to:
Tools → Plugin and Content Manager

or press:
Ctrl + M

Click on the Libraries tab.

Look for "KiCad FabLib" in the list of available libraries under the Libraries tab.

Click the Install button next to KiCad FabLib.

After installation, click Apply Pending Changes to complete the process.

When searching for components in the schematic or PCB editor, installed fab library components appear with the prefix fab in the search results.

So I imported the needed components from the Fablab library.

Rotating and Flipping Before Placement

• Press R to rotate 90°.
• Press X to flip horizontally.
• Press Y to flip vertically.

Adding Values to Symbols

Think of the Value as the price tag on a component. It tells you what that component is. For example, a resistor worth 10k ohms, a capacitor of 100nF, or a chip called AMS1117-3.3. Without a value, the symbol is just a shape with no meaning.

Method 1 — Double-click the symbol

1. Place the symbol on the schematic.
2. Double-click it to open the Symbol Properties dialog.

3. Find the Value row in the fields table.
4. Click the cell in the Value column and type the component value (example: 10k, 100nF, 2N2222).

5. Click OK to apply.

Method 2 — Double-click the value text directly

1. On the schematic, find the value text sitting below or beside the symbol (it shows the current value, for example R or C by default).
2. Double-click that text label.
3. A small edit box appears — type the new value directly.
4. Press Enter to confirm.

Method 3 — Press E with the symbol selected

1. Single-click the symbol to select it.
2. Press E on the keyboard.
3. The Symbol Properties dialog opens — edit the Value field.
4. Click OK.

Editing Other Component Properties

• Double-click the placed component.
• Edit:
  • Reference (Example: R1, C1)
  • Value (Example: 10k, 100nF)
  • Footprint (Important for PCB design)
  • Datasheet link (optional)

What is a Footprint?

A footprint defines the physical layout of a component on the PCB. It includes pad size, pad spacing, drill holes, and overall package shape. The schematic symbol and PCB footprint are separate and must be linked.

Wiring and Electrical Checks

Add Wires

1. Press W.
2. Click from one pin to another.
3. Press Esc to stop wiring.

We added the ATtiny412 directly from the fab library.

We added a push button to the circuit.

Global Labels

A Global Label is like a name tag you stick on a wire. If two pins have the same name tag, KiCad treats them as connected even if they are far apart or on completely different schematic sheets. No wire needs to be drawn between them.

How to place a Global Label:

1. Move your cursor to the pin or wire end where you want to attach the label.
2. Press Ctrl + L, or go to Place Global Label in the rightmost toolbar.

3. In the dialog that appears, type the label name (example: SDA, VCC, UART_TX).

4. Choose the Connection Type:
   • Input — signal enters this component through this pin.
   • Output — signal leaves this component through this pin.
   • Bidirectional — signal can travel in either direction (common for data lines).
   • Tri-state — pin can be driven high, low, or left floating.
   • Passive — direction is not specified (use for power or generic nets).
5. Click OK.
6. Click at the exact end of a pin or wire to attach the label. The label must snap to a pin or wire endpoint — a dangling label is flagged as an ERC error.
7. Press Esc to stop placing labels.

To create the matching connection on another component or sheet, repeat the same steps and type the identical label name. KiCad treats all global labels with the same name as one continuous net.

I used this website to calculate the resistor value for the LED: LED Resistor Calculator

Run Electrical Rules Check (ERC)

Click on ERC in the top toolbar or go to Inspect → Electrical Rules Checker.

In the ERC window, click Run to analyze the schematic for electrical issues.

Review all reported errors and warnings. Double-click on each issue to locate it in the schematic and correct the problem.

Repeat the process until no unresolved errors or critical warnings remain.

PCB Design

Once the schematic is verified, open the PCB Editor from the KiCad Project Manager by clicking on PCB Editor.

To transfer the design from the schematic to the PCB layout, return to the Schematic Editor and select Tools → Update PCB from Schematic. In the update window that appears, click Update PCB.

PCB Trace (Routing Tracks) in KiCad

A PCB trace is a copper path that electrically connects component pads on the PCB. It replaces the wires from your schematic.

1. Update PCB from schematic.
2. Arrange all component footprints properly.

To do this, you can click and drag them to the desired positions.


3. Set proper track width (based on current requirements).

Setting Constraints in the PCB Editor

Constraints tell KiCad the rules your board must follow. Things like how thick a copper track must be, how much space to leave between tracks, and how large drill holes should be. Getting these right before you start routing saves you from having to redo everything later.

Go to File → Board Setup (or press Ctrl + Shift + P).

This opens the Board Setup window. The constraints you need are under Design Rules → Constraints in the left sidebar.

• Minimum track width — the thinnest a copper track can be. For PCB milling in a Fab Lab, use 0.4 mm or wider. Thinner tracks break easily when milled.
• Minimum clearance — the smallest gap allowed between any two copper shapes. Use 0.4 mm for milling; commercial fabs can go as low as 0.1 mm.
• Minimum annular width — the ring of copper around a drill hole. A value of 0.3 mm is a safe minimum.
• Copper to edge clearance — how far copper must stay from the board edge. Use at least 0.5 mm to avoid shorts during milling.

How to set a constraint

1. Find the constraint you want to change (e.g. Minimum track width).
2. Click the value next to it and type your new number.
3. Click OK to save and close.

Routing Traces

Step 1: Select Route Tool

1. Open PCB Editor.
2. Press X on your keyboard.
3. Or click the Route Tracks icon from the right toolbar.

Step 2: Start Routing

Click on the target pad and drag the mouse.

Click again when you reach the destination pad.

• Follow the white ratsnest line as a guide.

Routing Tips

• Keep traces short and clean.
• Avoid sharp angles (use 45° angles).
• Avoid crossing traces on the same layer.
• Maintain proper spacing between tracks.

Deleting a Trace

• Click on the trace.
• Press Delete.

Dragging or Adjusting Trace

• Hover over the trace.
• Press G to drag while keeping connections.

Edge Cut in KiCad PCB Editor

1. Select Edge.Cuts layer

2. Select 'Draw Rectangle' tool
3. Draw board boundary
4. Ensure closed shape

Alternative Method: Draw Rectangle Using Lines

1. Select Add Graphic Line.
2. Click to draw the first edge.
3. Draw four lines (top, right, bottom, left).
4. Ensure the final line connects exactly to the starting point.

• The shape must be fully closed with no gaps.

Check Design Rules

1. Click Inspect → Design Rules Checker (DRC).

2. Fix any clearance or connection errors.

The Edge.Cuts layer defines the physical boundary of the PCB. This outline tells the manufacturer where the board should be cut. The shape must always be a fully closed loop.

3D Viewer in KiCad PCB Editor

The 3D Viewer allows you to see your PCB in a realistic 3D model. It helps you check component placement, board shape, and overall design appearance before fabrication.

Step 1: Open PCB Editor

1. Open your project.
2. Click PCB Editor.

Step 2: Open 3D Viewer

1. Click View in the top menu.
2. Select 3D Viewer.
3. Or press Alt + 3 (shortcut).

A new window will open showing your PCB in 3D.

Basic Controls in 3D Viewer

• Left Mouse Button: Rotate the board.
• Middle Mouse Button: Pan (move view).
• Mouse Scroll: Zoom in/out.
• Right Mouse Button: Context options.

If Components Do Not Appear in 3D

• Footprints may not have 3D models assigned.
• Open footprint properties.
• Assign a 3D model file (.step or .wrl).

Individual Project

Overview

For the individual assignment, I designed a PCB for the LED blinker circuit I had previously built and simulated during the Electronics week. This board was built on Xiao RP2040. The goal was to take that design and turn it into a real, fabrication ready PCB layout using KiCad.

XIAO Wiki

Downloading Additional Components

Not all components are available in KiCad's default library. For this project, I needed a S4B-PH-SM4-TB connector, which was not available in KiCad. I downloaded it from SnapMagic, a library of ready-to-use schematic symbols and footprints. This is a useful method whenever a component is missing from KiCad's built-in libraries.

Adding the Component to KiCad

Once downloaded, I imported the component into KiCad by adding it to a local library. The downloaded package includes both the schematic symbol and the PCB footprint, so it can be used directly in the schematic editor and then carried through to the PCB layout.

Design Rules Check (DRC)

Once routing was complete, I ran the Design Rules Checker (DRC) in KiCad to do a full automated inspection of the routed board. DRC compares every copper feature, pad, via, and board outline against the constraint values set in the Board Setup, such as minimum trace width (0.4 mm for the Fab Lab Roland MDX milling machine) and minimum clearance between copper objects (0.4 mm). Any violation is flagged with its exact location on the canvas so it can be found and fixed immediately.

The DRC report covered the following checks:

• Clearance violations — two copper features closer than the allowed minimum, which would merge during milling and cause shorts.
• Unconnected nets — pads that the schematic says must be connected but have no routed trace yet.
• Minimum trace width — traces too narrow for the mill bit to cut cleanly without breaking.
• Board outline integrity — missing or overlapping segments in the Edge.Cuts layer that would confuse the milling path.
• Footprint courtyard overlaps — component keep-out areas that overlap, indicating components placed too close to solder cleanly.

After running DRC, I addressed each flagged item, adjusting trace routes or clearances as needed, until the checker reported zero errors. Only then did I proceed to measure board dimensions and export for fabrication.

Routing Traces

With all components placed in the schematic, I opened the PCB Editor and arranged them within the board outline. I kept the layout compact while maintaining enough clearance between parts for reliable fabrication.

I routed all the copper traces manually, connecting the pads according to the ratsnest (the unconnected net lines from the schematic). I used appropriate trace widths for power and signal lines to ensure the board meets fabrication requirements.

3D Preview

I used KiCad's 3D Viewer to do a final visual check of the board — confirming component placement, orientation, and the overall footprint of the design before exporting.

Exporting Gerber to PNG

Before using Fab Mods, I exported the PCB layers from KiCad as Gerber files, then converted them to high-resolution PNG images, the format required by Fab Mods to generate milling toolpaths.

Step 1: Open Fabrication Outputs

In the PCB Editor, go to File → Fabrication Outputs → Gerbers (.gbr)

Step 2: Configure the Plot (Gerber) settings

The Plot dialog opens. Check the following settings before clicking Plot:

• Plot format — make sure it is set to Gerber.
• Output directory — choose a folder where the files will be saved.
• Include Layers — tick the layers you need. At minimum:
  • F.Cu — front copper (your traces)
  • B.Cu — back copper (if double-sided)
  • F.Mask / B.Mask — solder mask openings
  • F.Silkscreen / B.Silkscreen — component labels
  • Edge.Cuts — board outline (required)
• Coordinate format — leave at 4.6, unit mm.
• Keep Use extended X2 format and Generate Gerber job file ticked.

Click Plot. The Output Messages box at the bottom will show Done. for each layer when it finishes.

Step 3: Generate Drill Files

After plotting the Gerbers, click Generate Drill Files... at the bottom right of the Plot dialog. A new window opens.

• Output folder — use the same folder as your Gerber files.
• Format — leave as Excellon (the standard for most fabs and milling machines).
• Units — set to Millimeters.
• Zeros — leave as Decimal format (recommended).
• Origin — leave as Absolute.

Click Generate. Two drill files are created: PTH.drl (plated through-holes) and NPTH.drl (non-plated holes).

Step 4: Check the output files

Open the output folder. You should see a set of .gbr files (one per layer) and two .drl drill files:

• hw-F_Cu.gbr — front copper layer (traces)
• hw-B_Cu.gbr — back copper layer
• hw-F_Mask.gbr / hw-B_Mask.gbr — solder mask layers
• hw-F_Paste.gbr / hw-B_Paste.gbr — solder paste layers
• hw-F_Silkscreen.gbr / hw-B_Silkscreen.gbr — silkscreen labels
• hw-Edge_Cuts.gbr — board outline
• hw-job.gbrjob — job file that groups all Gerbers together
• hw-PTH.drl — plated drill holes
• hw-NPTH.drl — non-plated drill holes

Zip all these files together and send them to your PCB manufacturer, or load them into a Gerber viewer (like KiCad's built-in viewer or Fab Mods) to verify before fabrication.