I2C SENSOR (RTC)

CODE

#include <stdio.h>
#include "hardware/i2c.h"
#include "pico/binary_info.h"

// Hardware Configuration
#define I2C_PORT i2c1
#define PIN_SDA 6
#define PIN_SCL 7
#define DS3231_ADDR 0x68

// BCD conversion functions
uint8_t bcdToDec(uint8_t val) { return ((val / 16 * 10) + (val % 16)); }

void setup() {
  Serial.begin(115200);
  
// Wait for serial monitor
  while (!Serial && millis() < 3000);

// Initialize I2C
  i2c_init(I2C_PORT, 100 * 1000);
  gpio_set_function(PIN_SDA, GPIO_FUNC_I2C);
  gpio_set_function(PIN_SCL, GPIO_FUNC_I2C);
  
// Active pull-ups
  gpio_pull_up(PIN_SDA);
  gpio_pull_up(PIN_SCL);

  Serial.println("--- MODO LECTURA: Reloj DS3231 Activo ---");
}

void loop() {
  uint8_t reg = 0x00; // Start recording (seconds)
  uint8_t data[3];    // Buffer for [0]=sec, [1]=min, [2]=hours


  i2c_write_blocking(I2C_PORT, DS3231_ADDR, ®, 1, true);
  

  int bytes_read = i2c_read_blocking(I2C_PORT, DS3231_ADDR, data, 3, false);

  if (bytes_read < 0) {
    Serial.println("Error: No se detecta el reloj. Revisa cables.");
  } else {
// Convert data from BCD to Decimal
    uint8_t segundos = bcdToDec(data[0]);
    uint8_t minutos  = bcdToDec(data[1]);
    uint8_t horas    = bcdToDec(data[2] & 0x3F); // Mask for 24h format


    Serial.print("\nHora actual: ");
    
    if (horas < 10) Serial.print('0');
    Serial.print(horas);
    Serial.print(':');
    
    if (minutos < 10) Serial.print('0');
    Serial.print(minutos);
    Serial.print(':');
    
    if (segundos < 10) Serial.print('0');
    Serial.print(segundos);
    

    Serial.print("\t");
  }

  delay(1000);
}


 

RESULT

ANALOGIC SENSOR

The Sharp sensor is connected as follows: the blue arrow can also be connected to a programming pin so that we can activate and deactivate it in operation; having it connected to VCC, the sensor will always be active.

CODE

  
const int sensorPin = A2;

void setup() {
  Serial.begin(115200);
  
  // Use the native resolution of the RP2350 (12-bit)
  analogReadResolution(12); 
  
  pinMode(sensorPin, INPUT);
  Serial.println("GP2Y0E02A Sensor ready...");
}

void loop() {
  // 1. Read raw value (0 - 4095)
  int rawValue = analogRead(sensorPin);
  
  // 2. Convert to Voltage (3.3V Reference)
  float voltage = rawValue * (3.3 / 4095.0);

  // 3. Calculate distance in cm using the datasheet slope
  // Using the linear equation: y = mx + b
  // Based on datasheet points: (0.55V, 50cm) and (2.2V, 4cm)
  float distanceCm = (voltage - 2.2) * (50.0 - 4.0) / (0.55 - 2.2) + 4.0;

  Serial.print("Voltage: ");
  Serial.print(voltage, 2);
  Serial.print("V | Distance: ");
  
  // 4. Range validation and output
  if (distanceCm > 55) {
    Serial.println("Fuera de rango (Lejos)");
  } else if (distanceCm < 3) {
    Serial.println("Fuera de rango (Cerca)");
  } else {
    Serial.print(distanceCm, 1);
    Serial.println(" cm");
  }

  delay(100); 
}

  

RESULT

STEP RESPONSE

I made this sensor with the help of Adrian Torres' documentation and Neil Gershenfeld's examples. What this sensor does is that its value increases when our hand approaches because the space between the two pieces of copper is reduced, which causes the capacitance to change.

The first thing I did was design a PCB to connect my sensor; we need two pins to connect our XIAO, which are an analog pin and a digital pin.

One of the copper plates is connected to two 1M ohm resistors that must go one to VCC and the other to GND; this connection goes to the analog pin, and the other copper plate goes to the digital pin.

This is the schematic of my board; the files to manufacture this board can be found in the files section.

CODE

long result;            // Stores the total sum of samples
int analog_pin = A2;    // Receiver pin where capacitance is measured
int tx_pin = D10;       // Transmitter pin 
 
void setup() {
  // Configures the transmitter pin as data output
  pinMode(tx_pin, OUTPUT);      
  
  Serial.begin(115200);
  
  delay(1000); 
}
 
long tx_rx() {
  int read_high;    // Variable for reading with active pulse
  int read_low;     // Variable for reading with deactivated pulse
  int diff;         // Difference between charge and discharge
  long sum = 0;     // Accumulator for all samples
  int N_samples = 100; // Number of measurements to average and reduce noise
 
  for (int i = 0; i < N_samples; i++) {
    
    digitalWrite(tx_pin, HIGH);
    read_high = analogRead(analog_pin);
    
    delayMicroseconds(100); 
 
    digitalWrite(tx_pin, LOW);
    read_low = analogRead(analog_pin);
    
    diff = read_high - read_low;
 
    sum += diff;
  }
  
  return sum; // Returns the total of the 100 samples
}
 
void loop() {
  result = tx_rx();
 
  // Converts the summed value (approx range 15000-25000) to a scale of 0 to 1024
  long mapped_result = map(result, 15000, 25000, 0, 1024); 
 
  Serial.print("Raw (Crudo): ");
  Serial.print(result);
  Serial.print(" | Mapped (Escalado): ");
  Serial.println(mapped_result);
 
  delay(50); 
}
      
      

RESULT