Import code from old repository from 2018

Old repository: https://github.com/binaryDiv/z80_computer

firmware_src/uart.h

@@ -0,0 +1,22 @@
+#ifndef UART_H_
+#define UART_H_
+
+#include "config.h"
+#include <avr/io.h>
+
+// Initialize UART
+void uartInit();
+
+// Transmit a single character
+void uartPutChar(unsigned char data);
+
+// Transmit a string
+void uartPutString(char* data);
+
+// Read a single character (blocking)
+unsigned char uartGetChar();
+
+// Read a string until \n (blocking)
+uint8_t uartGetLine(char* buffer, uint8_t maxLength);
+
+#endif /* UART_H_ */