11. Input Devices

Reflection

Group Assignment

Attached is the link to group assignment

Individual Assignment

• ☑ Linked to the group assignment page
• ☑ Documented what you learned form interfacing an input device(s) to microcontroller and how the physical property relates to the measured results
• ☑ Documented your design and fabrication process or linked to the board you made in a previous assignment
• ☑ Explained the programming process/es you used
• ☑ Explained any problems you encountered and how you fixed them
• ☑ Included original design files and source code
• ☑ Included a 'hero shot' of your board

What I Learned from Interfacing an Input Device to a Microcontroller

I summarised the important learning to me in table below. another interesting information is that lower baud rate is better for longer distances.

Command/Function	Description	Usage Tips
pinMode()	Sets the mode of a pin as INPUT or OUTPUT.	Ensure TRIG pin is set as OUTPUT and ECHO pin as INPUT.
delayMicroseconds()	Pauses the program for the specified number of microseconds.	Use after setting TRIG pin HIGH to create the correct pulse length.
Serial.begin()	Initializes serial communication at specified baud rate.	Use to output distance readings to the Serial Monitor for debugging and monitoring.
Calculating Distance	Uses the speed of sound in air and pulse duration to calculate distance.	The distance is typically calculated as (duration in microseconds * 0.034 / 2).
Power Supply Considerations	Ensures stable voltage and sufficient current for sensor operation.	HC-SR04 typically requires 5V; .

My Design and Fabrication Process

I looked at the datasheet of HC­SR04 Ultrasonic Sensor guide and . HC­SR04 Ultrasonic Sensor data. a screenshoot of important points is listed below. I summarrized the keypoints in table below.


Aspect	Specification	Purpose	Field
Dimensions	45*20*15mm	I may need to design the space in the 3D model to fit the sensor.	3D Design
Operating Voltage	DC 5 V	To ensure the sensor receives the correct voltage for operation. Luckily that esp32 have a VCC pin that outputs 5V	Electronic Design
Working Current	15mA	Important for designing power supply and ensuring adequate current. I cant find in the working current datasheet for esp32c3 xiao specific pins. But when i search internet mentions total current output of 700mA	Electronic Design
Working Frequency	40Hz	I sends out 40 waves per second. Useful if i want to work the sensor from raw principles instead of using the library.	Programming
Measuring Angle	15 degrees	I can use it for determining the field of view in designs and for calculating distances.	3D Design
Maximum Range	4m	If I want to consider sensor's range of detection.	Programming
Minimum Range	2cm	Important forme to know the closest measurable distance.	Programming
Trigger Signal	10µs TTL pulse	Specifies the trigger signal length for activating the sensor if I want to use sensor without default lib.	Electronic Design
Echo Signal	Input TTL level pulse width proportional to range	The echo signal duration is used to calculate the distance to an object if I want to use sensor without default lib.	Programming

i connected Distance Sensor to GPIO 6 and 7 of my Esp32 C3 Xiao.


Next I head to my programming


The Programming Process I Used

For programming, I used the Arduino IDE to write and upload the C++ code to the ESP32 XIAO C3. My code initializes the sensor and controls how it sends out pulses and reads the echo to calculate distances. The continual distance reading and calculation are managed in the loop function, and results are displayed on the serial monitor to provide real-time feedback.

Source Code

The following is the source code used for controlling the servo motor in our project. It utilizes the ESP32Servo library and is written in C++ for the Arduino programming environment:

                #include 

                    // Define the connections to the HC-SR04
                    const int trigPin = 6  ; // SCL; 
                    const int echoPin = 7  ; // SDA;
                    
                    void setup() {
                      // Initialize Serial Monitor
                      Serial.begin(115200);
                    
                      // Configure the trigger and echo pins
                      pinMode(trigPin, OUTPUT);
                      pinMode(echoPin, INPUT);
                    }
                    
                    void loop() {
                      // Ensure the trigger pin is set low
                      digitalWrite(trigPin, LOW);
                      delayMicroseconds(2);
                    
                      // Trigger the sensor by setting the trigPin high for 10 microseconds
                      digitalWrite(trigPin, HIGH);
                      delayMicroseconds(10);
                      digitalWrite(trigPin, LOW);
                    
                      // Read the echoPin, returns the sound wave travel time in microseconds
                      long duration = pulseIn(echoPin, HIGH);
                    
                      // Calculate the distance
                      long distance = duration * 0.034 / 2; // Speed of sound wave divided by 2 (go and return)
                    
                      // Display the distance on the Serial Monitor
                      Serial.print("Distance: ");
                      Serial.print(distance);
                      Serial.println(" cm");
                    
                      // Delay a short period of time to ensure accurate readings
                      delay(500);
                    }
                    
            

Challenges I Encountered and My Solutions

I have a messy table. Not much problem. I previously designed and documented my onboard and placed a rotary encoder and led inside my dev board made of ATTINY1614 but as I use Arduino to programme it. Below is demonstrate of me turning the encoder and triggering the led and offing itself after time limit. But as I did not made my own programmer so i redo the board for ESPP32. Below is the recording

Hope this time ESP32 is sufficiently done! Honestly I think i have a messy table.

Original Design Files and Source Code

Refer to code above and connection in the picture.

Hero Shot of My Board

Below is a 'hero shot'.





Understanding Input Methods in Electronic Systems

Effective interaction with the external environment is crucial for electronic systems, achieved through various input methods and components. This section delves into ports, comparators, A/D converters, and I2C communication, explaining their functions and applications.

Input Method/Component	Description	Applications
Ports	Physical interface points on microcontrollers used to connect external devices and sensors.	Used for digital and analog signal inputs, allowing microcontrollers to read data from switches, sensors, and other input devices.
Comparator	An electronic component that compares two voltages and outputs a digital signal indicating the higher voltage.	Commonly used in applications requiring threshold detection, such as battery level indicators and light sensors.
A/D (Analog-to-Digital Converter)	Converts analog signals into digital data that microcontrollers can process.	Essential for applications involving analog sensors, such as temperature or light intensity measurements, allowing digital systems to interpret analog inputs.
I2C (Inter-Integrated Circuit)	A serial communication protocol that uses two wires (SDA for data, SCL for clock) to connect multiple devices.	Enables communication between microcontroller and various peripherals like displays, sensors, and other ICs with minimal wiring, facilitating complex data exchange in a multi-device setup.