Group Assignment

For this week group assignment we should use the test equipment in your lab to observe the operation of a microcontroller circuit board. The complete group testing report is available on the Fablab Dilijan Group Assignment Page. I'm using Siglent SDS 1202x-e digital oscilloscope for testing arduino uno board two led digitalwrite to digitalwriteFast comparison.

Siglent SDS 1202x-e Specifications:

• Bandwidth: 200 MHz
• Channels: 2 Analog
• Sample Rate: 1 GSa/s (Max)
• Memory Depth: 14 Mpts
• Waveform Capture Rate: 100,000 wfm/s (Normal mode)
• Serial Decoding: Free standard support for I2C, SPI, UART, CAN, and LIN.
• Display: 7-inch color TFT-LCD with 256-level intensity grading.

I used two led bulbs with 200 ohm resistors and connected it to 3-4 digital pins on arduino uno board. I've installed digitalWriteFast by Watterott library
and used this code to compare digitalwrite and digitalwriteFast.

	#include "digitalWriteFast.h"
	void setup() {
	// put your setup code here, to run once:
	pinMode(3,OUTPUT); // led 1 pin
	pinMode(4,OUTPUT); // led 2 pin
	}

	void loop() {
	// Test Digitalwrite on led 1
	digitalWrite(3, HIGH);
	digitalWrite(3, LOW);
	// Test DigitalWriteFast on led 2

	digitalWriteFast(4,HIGH);
	digitalWriteFast(4,LOW);

	}

	

Oscilloscope Setup:

• Grounding: Connect the probe’s ground clip to the Arduino GND.
• Coupling: Use DC Coupling.
• Horizontal Scale (Timebase): Start at 5us for standard digitalWrite and dial down to 100ns for the fast version.
• Trigger: Set the trigger to Rising Edge and adjust the level to about 1.5V.

Test Results:

Device	DigitalWrite Speed	DigitalWriteFast Speed	Speed Factor
Arduino Uno	~6000 ns	~125 ns	~48x faster
ESP32	~500 ns	~50 ns	~10x faster

Individual Assignment

The goal this week was to design a custom development board from scratch. The board must include a microcontroller and peripherals to allow for interaction (input/output) and communication (serial/programming).

I chose KiCad 9.0 as my EDA (Electronic Design Automation) tool, because i had a little experience with Easyeda and wanted to try something new.
Before designing, I integrated the Fab Academy 2026 library to ensure all parts used are available in our lab's inventory.

• Symbols: Preferences > Manage Symbol Libraries -> Added fab.kicad_sym.
• Footprints: Preferences > Manage Footprint Libraries -> Added fab.pretty.

I designed a board based on the Seeed Studio XIAO ESP32C3 (or your preferred MCU from the inventory). Components Used:

• Microcontroller: Seeed Studio XIAO ESP32C3.
• Input: 1x Push Button (OMRON B3F-1000).
• Output: 1x LED (1206 SMD) with a 330 ohm current-limiting resistor.
• Power: $10\mu F$ Decoupling Capacitor to stabilize the voltage.
• Connectors: 1x6 Pin Header for external communication/FTDI.

To verify the circuit before fabrication, I simulated the LED trigger logic.
I also exported the netlist to LTspice to perform a more granular stress test on the power regulation, simulating the voltage drop when the ESP32 switches from Sleep to Active mode.

Schematic Design in KiCad

I connected the XIAO pins to peripherals: GPIO2 is mapped to the output LED, GPIO3 to the input push button (with an internal pull-up resistor enabled in software), and the UART TX/RX pins are routed to the 1x6 header for serial debugging and firmware flashing.

PCB Layout & Routing

• Assigning Footprints: I matched schematic symbols to hand-solderable 1206 SMD footprints from the Fab library.
• Routing Traces: I used a 0.4mm trace width to ensure traces can be milled reliably on our CNC router without lifting. Power traces (VCC and GND) were routed with 0.6mm width to support higher current spikes.
• Design Rule Check (DRC): Configured minimum clearance to 0.4mm (based on our 1/64" PCB milling bit size) and ran the DRC. No errors or disconnected nets were found.

Original Design Files

Download the KiCad project files and schematic exports below:

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Week 6 — Summary

This week focused on EDA schematics, routing constraints, and testing. Here is a summary of the accomplishments: