The final lab of the Spring 2025 semester introduced us to real-time operating systems (RTOS) for embedded systems. We ran a series of Arduino sketches on the ESP32S3 that demonstrate essential RTOS capabilities, such as task scheduling, memory allocation, queuing, and multicore operations. The video below demonstrates the functionality of all 7 exercises, and code screenshots for each exercise can be found after the video.

Scheduling LED blinks at different speeds without using the main 

Prioritization of tasks using non-blocking logic. 

Inter-task communication to avoid stack overflows and task conflicts. 

) to control access to shared resources (e.g., global variables) 

Run tasks on multiple cores of the ESP32 to improve efficiency

This project streams live video over WiFi and simultaneously stores static images on the SD card. I was not able to use the code provided in class, so I combined the camera timer functionality from the code provided in class with an example Arduino sketch (Examples/ESP32/Camera/CameraWebServer). 

Week 14 - Real-Time Operating System (RTOS)

This lab entailed the creation of a motor controller using pulse-width modulation (PWM) to change the speed of a DC-motor.

The circuit includes the XIAO ESP32-S3, a small DC motor, one transistor (TIP120), one diode (IN914), two push buttons, one 4.7kΩ resistor, and two 1kΩ resistors (for the buttons). We also used the XIAO expansion board, which allowed us to power the motor using a dedicated LiPo battery, rather than powering it directly from the microcontroller. Our challenge was to use the push buttons to change the motor speed by adjusting the motor's duty cycle via PWM. 

The defining feature of our code was the use of interrupts to handle changes in fan speed. The interrupt routines were instantiated in the 

 function, and allowed us to control the fan speed asynchronously in response to hardware button presses. 

We had some issues getting the circuit to respond to button presses consistently, and the oscilloscope in the video shows quite a bit of noise in the circuit. This may have been due to defective buttons or loose jumper cables, but you can see the basic functionality of the system in the video below. 

The code used for our demo can be downloaded 

Week 13 - Motor Controller 

 to design a simple printed circuit board (PCB) for an LED circuit. We started the lab by creating the schematic, and concluded by generating a 3D render and exporting the files necessary to produce the PCB. 

The circuit consists of a JST connector (J1), resistor (R1), and LED (D1). We used this schematic to 

Next, we used the PCB Editor to arrange the components on the board, create a board outline, and route the traces between components.

Before exporting our PCB, we checked for errors using the Design Rules Check (DRC).

We completed the project by exporting the Gerber files necessary for production. These files include the copper layers, drill files, edge cuts, and silkscreen layers necessary to manufacture the PCB.   

KiCad also includes a feature to display a nicely rendered 3D model of the PCB design. The results of my work are shown below. 

The files I created for this lab can be downloaded 

James Cole

Week 6 - PCB Design

Schematic

PCB Layout

Finalized assets

3D Render

File download

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Week 14 - Real-Time Operating System (RTOS)

Week 13 - Motor Controller