usart character output

platformio.ini

@@ -11,7 +11,7 @@
 [env:pro16MHzatmega328]
 platform = atmelavr
 board = pro16MHzatmega328
-monitor_speed = 115200
+monitor_speed = 9600
 lib_deps =
     https://github.com/Sylaina/bme280.git
 

src/main.c

@@ -3,12 +3,38 @@
  * See LICENSE for details.
  */
 
+#define F_CPU 16000000UL
+#define BAUD 9600
+
 #include <avr/io.h>
 #include <util/delay.h>
+#include <util/setbaud.h>
 
 #include "bme280.h"
 #include <stdio.h>
 
+
+void uart_init(void) {
+    // Set baud rate
+    UBRR0H = UBRRH_VALUE;
+    UBRR0L = UBRRL_VALUE;
+
+    // Don't use double rate
+    UCSR0A &= ~(1 << U2X0);
+
+    // Enable rx and tx
+    UCSR0B = (1 << TXEN0) | (1 << RXEN0);
+
+    // Set frame format: 8-N-1
+    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);
+}
+
+void uart_putchar(char c) {
+    while(!(UCSR0A & (1 << UDRE0)));
+
+    UDR0 = c;
+}
+
 int main(void)
 {
     // make the LED pin an output for PORTB5
@@ -24,12 +50,14 @@ int main(void)
     pressure = bme280_readPressure(0);
     humidity = bme280_readHumidity(0);
 
+    uart_init();
 
     while (1)
     {
         _delay_ms(1000);
+        uart_putchar('!');
 
-        printf("Temp: %f\tPressure: %f\tHumidity: %f\n", temp, pressure, humidity);
+        //printf("Temp: %f\tPressure: %f\tHumidity: %f\n", temp, pressure, humidity);
 
         // toggle the LED
         PORTB ^= 1 << 5;