Output devices

• Group assignment:
• Measure the energy consumption of an output device.
• Document your work on the group work page and reflect on what you learned on your individual page.
• Individual assignment:
• Add an output device to a microcontroller board you've designed and program it to do something.

GROUP ASSIGNMENT

Link to group assignment

https://fabacademy.org/2026/labs/lima/Weeks/Week10/Week10.html

Aim

Characterize the energy consumption of an output device by measuring voltage and current, interpreting its influence on system performance and its integration within a microcontroller-based architecture.

Measuring energy consumption

To determine the energy consumption of the system, two fundamental variables were measured: voltage (V) and current (I), using a digital multimeter.

The electrical power was calculated using the following relationship:

P = V × I

Procedure

• The multimeter was connected in series to measure the current of the operating system
• The voltage was measured in parallel at the power supply terminals
• Measurements were taken with the system active to obtain real consumption values

Results

• Voltage: 5V
• Current: ~11.2 mA
• Power:56.16 mW

Analysis

The results show reduced energy consumption, characteristic of optimized embedded systems. This power level allows the system to be powered by low-capacity sources, such as batteries or portable modules.

Furthermore, it is observed that consumption depends directly on the state of the output device and the active components in the circuit, which highlights the importance of properly selecting each element based on energy efficiency.

Learning Achieved

Through the group assignment, I learned how to measure and analyze the energy consumption of an output device by calculating voltage, current, and power. I understood the importance of energy efficiency in embedded systems and how power consumption affects system stability, autonomy, and performance. This activity also strengthened my understanding of integrating output devices into microcontroller-based applications while considering real-world energy requirements.

INDIVIDUAL ALLOCATION

Aim

Design and implement the control of an output device on a board based on XIAO ESP32-C3, with the purpose of representing processed information from the system in real time, validating the integration between input, processing and output in a functional embedded system.

My process

Output device used

AOLED display with I2C communicationas an output device, allowing real-time visualization of the data processed by the microcontroller.

Technical specifications:

• Power supply: 3.3V (compatible with XIAO ESP32-C3 logic)
• Communication interface: I2C (SDA / SCL)

Low energy consumption compared to other screens

• High resolution and contrast for clear viewing

Selection justification:

An OLED screen was chosen due to its energy efficiency, ease of integration via I2C, and ability to represent information more fully than simple output devices (such as LEDs).

Function within the system:

The screen acts as a user interface, displaying the soil moisture status (DRY / WET), allowing immediate interpretation of the information processed by the microcontroller.

Integration with the board (XIAO ESP32-C3)

The OLED screen was integrated directly onto the circuit board designed based onXIAO ESP32-C3, without the use of a protoboard, fulfilling the requirement of electronic manufacturing and connection in real hardware.

Connection implemented:

• VCC → 3.3V (regulated output of the XIAO)
• GND → GND (common reference)
• SDA → XIAO SDA pin (I2C data line)
• SCL → XIAO SCL pin (I2C clock line)

Technical considerations:

• We worked with the logic of3.3Vensuring electrical compatibility between the display and the microcontroller
• The protocol was usedI2Callowing a reduction in the number of pins and simplifying the circuit design
• A guarantee was providedcommon ground reference (GND)to avoid communication errors
• The correct I2C address of the device was verified for its initialization in the code

Integration criteria:

The direct connection to the board allows for greater system stability, reducing interference and common errors associated with temporary connections. Furthermore, this integration validates the previous electronic design and its functionality in a real-world environment.

Programming and control

A program was developed in the Arduino environment compatible with theXIAO ESP32-C3, using specific libraries for managing the OLED screen via I2C protocol.

#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);
const int sensorPin = 2;

void setup() {
  pinMode(sensorPin, INPUT);
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    while(true);
  }
  display.clearDisplay(); 
  display.setTextSize(1);
  display.setTextColor(WHITE);
}

void loop() {
  int state = digitalRead(sensorPin);
  display.clearDisplay(); 
  display.setCursor(0,10);
  if(state == HIGH){
    display.println("WET");
  } else {
    display.println("DRY");
  }
  display.display(); 
  delay(500);
}

Operating logic:

• The microcontrollerXIAO ESP32-C3It performs the digital reading of the sensor through the pin configured as input.

The received signal (HIGH/LOW) is interpreted as soil moisture condition

• Depending on the state, the system executes a conditional structure that defines the information to be displayed.
• The bookstoreAdafruit_SSD1306It manages I2C communication and screen writing.
• An internal graphics memory buffer is used, which is updated using display.display()

Relevant technical aspects:

• Use of the protocolI2Cthrough the Wire library for efficient communication

Device address:0x3C, previously verified

• Graphics buffer management to prevent flickering or rendering errors

Update frequency controlled by delay(500) for visual stability

Programming criteria:

The code is structured to maintain a continuous sensor reading and a periodic interface update, ensuring a real-time response without overloading the system.

System validation

The system was validated through functional tests and verification of the coherence between the input signal and the response of the output device.

Tests performed:

• Sensor activation under conditions ofwet and dry ground
• Continuous reading of the digital signal (HIGH / LOW)
• Observing the response on the OLED screen

Results obtained:

• The OLED screen responded correctly to the sensor's state changes.
• The information was updated in real time without significant delays.
• Consistency was maintained between the input signal and the display (WET / DRY)
• No I2C communication errors were detected during operation

Validation criteria:

• Stability:The system maintains continuous operation without failures
• Precision:The output corresponds correctly to the measured physical state.

Answer:The update time is adequate for the application

• Integrity:There are no signal losses or display errors.

Technical conclusion:

The validation confirms that the integration between sensor, microcontroller (XIAO ESP32-C3The output device is functional, stable, and suitable for real-time monitoring applications.

Final result – HERO SHOT

The developed system consists of a functional humidity monitoring solution, effectively integratinginput, processing and outputin a microcontroller-based architecture.

System capabilities:

• Soil moisture detection using HL-69 sensor
• Digital signal processing with the microcontrollerXIAO ESP32-C3
• Real-time information display via OLED screen
• Execution of conditional logic for data interpretation
• Complete integration of hardware and software on a functional board

Value of the result:

The project demonstrates the ability to design and implement a complete embedded system, where environmental data is captured, processed, and communicated to the user in a clear and efficient manner.

Problems and solutions

Problem 1: The LED did not light up

Solution:

The polarity of the LED and the pin connections in the circuit were checked.

Problem 2: The buzzer did not emit sound

Solution:

The output pin programming and the correct connection of the buzzer were verified.

Problem 3: The OLED screen was not displaying information

Solution:

The I2C connections and the screen address in the code were checked.

Learning achieved

During this week, we were able to understand the importance of output devices within an embedded system, understanding that their function is not limited to simply executing actions, but also to communicating information clearly and efficiently to the user.

We learned how to integrate and program an OLED screen using I2C communication with the XIAO ESP32-C3 microcontroller, correctly configuring the SDA and SCL connections, as well as the device address and the libraries necessary for its operation.

Furthermore, knowledge of Arduino IDE programming, handling conditional structures, and real-time information updates through graphical interfaces was strengthened. The relationship between input, processing, and output within a functional electronic system was also understood.

At a practical level, the system's operation was validated through soil moisture tests, observing how the microcontroller processes the sensor signal and represents the state on the OLED screen in a stable and accurate manner.

Furthermore, measuring energy consumption made it possible to understand the importance of designing efficient systems, especially in IoT applications and portable devices.

where controlling electricity consumption is fundamental to ensuring autonomy and stability.

📋 Check-off List

1. Linked to the group assignment page?

Yes. The link to the group page where the energy consumption measurement of the output device and the system analysis were performed was included.

2. Did you document how you and your group determined the energy consumption of an output device?

Yes. The measurement procedure was explained using a multimeter to obtain voltage and current, applying the power formula:

P=V×IP = V \times IP=V×I

In addition, the results obtained were documented: 5V, 11.2 mA and an approximate power of 56.16 mW.

3. Did you document what you learned by interfacing the output devices with the microcontroller and controlling them?

Yes. The integration of an I2C OLED display with the XIAO ESP32-C3 was documented, as well as how the microcontroller processes the sensor signal to display real-time information.

4. Is it linked to the board made previously, or did you document your design and manufacturing process?

Yes. We worked on the previously designed PCB with the XIAO ESP32-C3, directly integrating the OLED screen and other output devices.

5. Did he explain how his code works?

Yes. The program's operation in the Arduino IDE was explained, including sensor reading, conditional logic, and I2C communication with the OLED screen using the libraries.Wire,Adafruit_GFXandAdafruit_SSD1306.

6. Did you explain any problems encountered and how you resolved them?

Yes. Issues such as LED, buzzer, and OLED display failures were documented and resolved by checking polarity, connections, and I2C address.

7. Does it include original source code and new design files?

Yes. The source code used to control the OLED screen and the corresponding files for the electronic design integrated into the PCB were included.

8. Does it include a 'hero shot' on your board?

Yes. The hero shot was added showing the complete system in operation, with the moisture sensor, the XIAO ESP32-C3, and the OLED screen displaying the soil condition in real time.

❓ Frequently Asked Questions

1. Is it sufficient to use a simple LED as an output device for this task?

Answer:
No. In my case, I understood that a basic LED didn't meet the required level of complexity, since the task aimed to demonstrate a more complete system output. Therefore, I used devices like an I2C OLED display and also tested outputs such as a buzzer and LED within my Xiaomi ESP32-C3-based board, which allowed me to visualize real-time information and not just a simple status.

2. Can I use a breadboard to connect my output devices?

Answer:
No. During my development, I avoided using a breadboard and connected the output devices directly to the PCB I designed. This was important because the goal was to validate a real embedded system, not a temporary simulation. The OLED display and other components were soldered and connected directly to the board.