Change serial baud to 500k at double-speed; but add cmake option for serial rxmode

src/com232.c

@@ -20,9 +20,6 @@
     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
-#define USART_BAUD_RATE(BAUD_RATE)                                             \
-  (uint16_t)((float)(F_CPU * 64 / (16 * (float)BAUD_RATE)) + 0.5)
-
 #include <avr/interrupt.h>
 #include <avr/io.h>
 #include <avr/sfr_defs.h>
@@ -31,6 +28,15 @@
 #include "com232.h"
 #include "timing.h"
 
+#if USART_RXMODE == USART_RXMODE_CLK2X_gc
+#define RXMODE_S 9
+#elif USART_RXMODE == USART_RXMODE_NORMAL_gc
+#define RXMODE_S 16
+#endif
+
+#define USART_BAUD_RATE(BAUD_RATE)                                             \
+  (uint16_t)((float)(F_CPU * 64 / (USART_RXMODE * (float)BAUD_RATE)) + 0.5)
+
 uint8_t RS232_RxCharBuffer[25], RS232_RxCharBegin, RS232_RxCharEnd;
 uint8_t readkey;
 
@@ -44,11 +50,11 @@ void RS232_Init(void) {
 
   USART0.CTRLA = USART_RXCIE_bm;                 // Enable receive interrupts
   USART0.CTRLB = USART_RXEN_bm | USART_TXEN_bm | // Enable Rx/Tx and set receive
-                 USART_RXMODE_NORMAL_gc;         //  mode normal
+                 USART_RXMODE;                   //  mode
   USART0.CTRLC = USART_CMODE_ASYNCHRONOUS_gc | USART_PMODE_DISABLED_gc |
                  USART_CHSIZE_8BIT_gc |
                  USART_SBMODE_1BIT_gc; // Async UART with 8N1 config
-  USART0.BAUD = USART_BAUD_RATE(250000);
+  USART0.BAUD = USART_BAUD_RATE(500000);
 }
 
 ISR(USART0_RXC_vect) {