AVR-Playground/main.c

/*
 * This code utilizes the AVR libraries for I2C and UART communication.
 * Make sure to connect the SDA and SCL pins of the ATmega328P to the
 * corresponding pins of your I2C temperature sensor. Additionally, you might
 * need pull-up resistors for the I2C lines.
 */

#include <avr/io.h>
#include <util/delay.h>
#include <math.h>

#define LED_PIN PB5  // Define the pin connected to the LED
#define TEMP_SENSOR_ADDR 0x48
#define TEMP_REG_ADDR 0x00
#define BAUD 9600

void initI2C() {
    // Set the prescaler to 1
    TWSR &= ~(1 << TWPS0);
    TWSR &= ~(1 << TWPS1);
    // Set the bit rate to 100kHz
    TWBR = ((F_CPU / 100000) - 16) / 2;
}

void I2C_start() {
    // Send the start condition
    TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
    // Wait for the start condition to be sent
    while (!(TWCR & (1 << TWINT)))
        ;
}

void I2C_stop() {
    // Send the stop condition
    TWCR = (1 << TWINT) | (1 << TWSTO) | (1 << TWEN);
    // Wait for the stop condition to be sent
    while (TWCR & (1 << TWSTO));
}

void I2C_write(uint8_t data) {
    // Load the data into the data register
    TWDR = data;
    // Start transmission of data
    TWCR = (1 << TWINT) | (1 << TWEN);
    // Wait for the data to be sent
    while (!(TWCR & (1 << TWINT)));
}

uint8_t I2C_read(uint8_t ack) {
    // Enable TWI, generate ACK (if ack = 1) and clear TWI interrupt flag
    TWCR = (1 << TWINT) | (1 << TWEN) | (ack << TWEA);
    // Wait until TWI finish its current job (read operation)
    while (!(TWCR & (1 << TWINT)));
    // Return received data
    return TWDR;
}

void initUART() {
    // Set baud rate
    UBRR0H = (uint8_t)(F_CPU / (BAUD * 16UL) - 1) >> 8;
    UBRR0L = (uint8_t)(F_CPU / (BAUD * 16UL) - 1);
    // Enable receiver and transmitter
    UCSR0B |= (1 << RXEN0) | (1 << TXEN0);
    // Set frame format: 8 data, 1 stop bit
    UCSR0C |= (1 << UCSZ01) | (1 << UCSZ00);
}

void UART_transmit(uint8_t data) {
    // Wait for empty transmit buffer
    while (!(UCSR0A & (1 << UDRE0)));
    // Put data into buffer, sends the data
    UDR0 = data;
}

void UART_println(const char *str) {
    // Transmit each character until NULL character is encountered
    while (*str) UART_transmit(*str++);
    // Transmit carriage return and line feed characters
    UART_transmit('\r');
    UART_transmit('\n');
}

float readTemperature() {
    uint16_t temperature;

    // Send start condition
    I2C_start();
    // Send device address with write operation
    I2C_write((TEMP_SENSOR_ADDR << 1) | 0);
    // Send temperature register address
    I2C_write(0x00);
    // Repeat start
    I2C_start();
    // Send device address with read operation
    I2C_write((TEMP_SENSOR_ADDR << 1) | 1);
    // Read temperature data MSB
    temperature = (uint16_t)(I2C_read(1)) << 8;
    // Read temperature data LSB
    temperature |= I2C_read(0);
    // Send stop condition
    I2C_stop();

    // Convert raw data to temperature in Celsius
    return (float)temperature * 0.0625;
}

int main(void) {
    initI2C();
    initUART();

    float temperature;

    while (1) {
        temperature = readTemperature();
        // Print temperature over UART
        UART_println("Temperature: ");
        UART_transmit((uint8_t)(temperature / 10.0) + '0');
        UART_transmit((uint8_t)fmod(temperature, 10.0) + '0');
        UART_println(" °C");
        _delay_ms(1000);  // Delay for 1 second
    }

    return 0;
}

void blink() {
    // Set the LED pin as output
    DDRB |= (1 << LED_PIN);

    while (1) {
        // Turn on the LED by setting the pin high
        PORTB |= (1 << LED_PIN);
        // Delay for 500 milliseconds
        _delay_ms(500);

        // Turn off the LED by setting the pin low
        PORTB &= ~(1 << LED_PIN);
        // Delay for 500 milliseconds
        _delay_ms(500);
    }
}