added arduino, modified build

lib.h

@@ -0,0 +1,26 @@
+void uart_init() {
+    // Upper and lower bytes of the calculated prescaler value for baud.
+    UBRR0H = UBRRH_VALUE;
+    UBRR0L = UBRRL_VALUE;
+
+    // Configure data frame size to 8-bits.
+    UCSR0C = _BV(UCSZ01) | _BV(UCSZ00);
+
+    // Configure to enable transmitter.
+    UCSR0B = _BV(TXEN0);
+}
+
+void uart_putchar(char c) {
+    // Wait until the register to write to is free.
+    loop_until_bit_is_set(UCSR0A, UDRE0);
+
+    // Write the byte to the register.
+    UDR0 = c;
+}
+
+void uart_putstr(char *data) {
+    // Loop until end of string writing char by char.
+    while(*data){
+        uart_putchar(*data++);
+    }
+}