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 

This project used the sensing and wireless capabilities of the 

 to create a data logging system. A key feature of the design was the inclusion of a voltage divider, allowing us to monitor the battery power to halt or continue data logging relative to the voltage provided by the battery. 

We implemented voltage divider comprised of three resistors rated at 680Ω, 2.2kΩ, and 10kΩ. Two resistors are connected together in series, while the third resistor is connected to ground.

This is how we calculated the voltage for our battery monitor. 

The image below shows how the circuit was implemented on a breadboard.

The function on the next page uses the reading from pin 

 to calculate the battery voltage from the analog-to-digital converter (ADC) and prints the system status on the OLED. Our full code can be 

These screenshots show how our sensor readings and system status messages are printed to the serial monitor and written to the SD card. The 

Displaying battery voltage and data logging status on the OLED

James Cole

Weeks 3 and 4 - Smart Environmental and Activity Logger

Voltage Divider

Data logging

Bluetooth connectivity

Voltage measurement and sensor output

Demo

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Week 14 - Real-Time Operating System (RTOS)

Week 13 - Motor Controller