Fab Academy 2026

Group work only

Week summary

In this group assignment, we used laboratory measurement tools to observe the electrical behavior of a microcontroller board. We first checked the power rails with a multimeter and then used an oscilloscope to measure the output signal generated by a Seeed Studio XIAO RP2040.

Group assignment requirement: use test equipment in the lab to observe the operation of a microcontroller circuit board and document the work on the group page.

Quick data

Topic: Electronics Design
Student: Carmen Elena Gutierrez Apolinario, David Avila Pimentel, Esteban M. Valladares, Jianfranco Bazan J., Mario Chong, Rocio Maravi, Grace Schwan, Cindy Marilyn Crispin, Jennifer Wong.
Equipment: Oscilloscope and multimeter
Board: Custom PCB with Seeed Studio XIAO RP2040

Assignment and deliverable

Use the test equipment in your lab to observe the operation of a microcontroller circuit board.
As a minimum, demonstrate the use of a logic analyzer or equivalent signal observation workflow.
Document the work on the group work page.

Goal

The goal of this group assignment was to observe and analyze the electrical behavior of a microcontroller board using laboratory measurement tools. We focused on verifying stable power delivery and confirming that the board can generate a reliable digital signal.

Equipment used

Oscilloscope: GW Instek GDS-1152A (150 MHz, 2 channels)
Multimeter: PR-75 Digital Multimeter
Microcontroller board: Custom PCB with Seeed Studio XIAO RP2040
Power: USB

Equipment table

Tool	Model	How we used it
Digital oscilloscope	GW Instek GDS-1152A (Digital Storage Oscilloscope, 150 MHz, 2 channels)	Visualize waveforms over time, verify voltage levels, and check frequency stability.
Digital multimeter	PR-75	Check power rails (VCC/GND), confirm 3.3V logic level, and rule out shorts.
Microcontroller board	Custom PCB with Seeed Studio XIAO RP2040	Generate a digital GPIO signal to measure with the oscilloscope.
Power	USB	Power and program the board.

Procedure

1. Multimeter pre-check

Before connecting the oscilloscope, we used the multimeter to:

Verify the board was receiving correct power.
Measure voltage between GND and VCC.
Confirm the 3.3V logic level was stable.
Check continuity to rule out shorts before probing signals.

This step is important to ensure the board is safe and to avoid measuring a circuit with an accidental short.

2. Oscilloscope setup

We connected the oscilloscope as follows:

Ground clip (black) → board GND
Probe tip → output GPIO pin

Settings used:

Channel: CH1
Voltage scale: 1V/div
Time scale: 1ms/div
Trigger: Edge mode (CH1)
Auto Set for initial calibration

3. Signal observation

After programming the RP2040 to generate a square wave, we observed:

A clear digital square wave.
Voltage levels from 0V to approximately 3.3V.
Stable frequency according to the programmed timing.

This confirmed:

Correct microcontroller execution.
Proper GPIO output behavior.
Stable voltage regulation.

Code used (Arduino IDE - XIAO RP2040)

This code generates a square wave on a GPIO pin. Update PIN_OUT to match the pin used (D0, D1, etc.).

// Fab Academy - Week 6 (Group)
// Square wave test for oscilloscope / logic analyzer
// Board: Seeed Studio XIAO RP2040

const int PIN_OUT = D0;   // <-- CHANGE THIS PIN (D0, D1, etc.)
const int T_US    = 500;  // HIGH/LOW microseconds (500us+500us ≈ 1kHz)

void setup() {
  pinMode(PIN_OUT, OUTPUT);
  digitalWrite(PIN_OUT, LOW);
}

void loop() {
  digitalWrite(PIN_OUT, HIGH);
  delayMicroseconds(T_US);
  digitalWrite(PIN_OUT, LOW);
  delayMicroseconds(T_US);
}

Tip: If you want a slower signal to view more easily, increase T_US or use delay().

Results

The oscilloscope displayed a clean square wave signal, confirming that the microcontroller clock and firmware execution were working properly, the digital GPIO switched correctly between LOW and HIGH, and the board power supply remained stable during operation.

What we learned

How to connect an oscilloscope properly to an electronic board.
Why a solid GND reference is required for stable measurements.
The difference between measuring voltage with a multimeter and visualizing signals with an oscilloscope.
How real digital signals look in hardware.

Difficulties we faced

At first, it was not easy to get a clean and stable waveform on the oscilloscope. These were the main issues we ran into and how we solved them:

Ground not properly connected: the signal looked noisy or unstable when the probe ground clip was loose or connected to the wrong reference. Once we attached the ground clip firmly to the board GND, the waveform became stable.
Probing the wrong pin: at first we measured a pin that was not the GPIO configured in the code. We double-checked PIN_OUT and the board pin labels, then moved the probe to the correct GPIO output.
TIME/DIV and VOLTS/DIV not set correctly: with an incorrect time base, the square wave did not fit on the screen. After adjusting to around 1 ms/div and using 1 V/div, the waveform became clear.
Trigger settings: without a proper trigger, the waveform kept moving. After setting Edge trigger on CH1 and adjusting the trigger level, the waveform locked and became easy to read.
Probe attenuation mismatch: we checked the probe switch (x1/x10) and matched it with the oscilloscope channel setting to correct the voltage readings.
AUTOSET was not enough: it helped as a starting point, but we still needed manual tuning.

After fixing GND connection, confirming the correct GPIO pin, and setting trigger and scales properly, we finally observed a clean square wave around 0–3.3V with stable frequency.

Tips and recommendations

Multimeter first

Check VCC and GND to confirm the board is powered correctly.
Use continuity mode to rule out shorts between VCC and GND.
Make sure the board GND is accessible and clearly identified.

Oscilloscope setup

Always connect GND first.
Start with safe scales: around 1 V/div and 1 ms/div.
Use Edge Trigger on CH1 so the waveform stays stable.
Check probe setting (x1 / x10).
Use AUTOSET as a starting point, then fine-tune manually.

Key lesson: Multimeter first for power and no shorts, then oscilloscope with proper GND, scales, and trigger to quickly get a clean square wave.

Evidence gallery

Conclusion

This group assignment helped us understand how to safely verify a board before measuring signals, how to correctly connect the oscilloscope, and how to interpret a real digital signal in hardware. We also learned that proper grounding, correct GPIO selection, and good trigger and scale settings are essential to obtain a stable waveform and validate the operation of the microcontroller board.