Splitting code

i2c.c

@@ -0,0 +1,44 @@
+#include <avr/io.h>
+#include <util/delay.h>
+#include "i2c.h"
+
+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;
+}

i2c.h

@@ -0,0 +1,7 @@
+#pragma once
+
+void initI2C();
+void I2C_start();
+void I2C_stop();
+void I2C_write(uint8_t data);
+uint8_t I2C_read(uint8_t ack);

makefile

@@ -12,7 +12,7 @@ QEMU_MACHINE_NAME = uno
 CFLAGS = -std=c2x -Wall -Wno-array-bounds -mmcu=$(MCU) -DF_CPU=16000000UL -O3
 
 # Source files
-SRCS = main.c
+SRCS = $(wildcard *.c)
 
 # Object files
 OBJS = $(SRCS:.c=.o)

uart.c

@@ -0,0 +1,32 @@
+#include "uart.h"
+#include <avr/io.h>
+#include <util/delay.h>
+
+// 9600 seems to be the highest the ATmega328P can handle in this config
+#define BAUD 9600  
+#include <util/setbaud.h>
+
+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');
+}

uart.h

@@ -0,0 +1,7 @@
+#pragma once
+
+#include <stdint.h>
+
+void initUART();
+void UART_transmit(uint8_t data);
+void UART_println(const char *str);