init

1 files changed, 74 insertions, 0 deletions

diff --git a/src/uart.c b/src/uart.c
new file mode 100644
index 0000000..3ba75db
--- /dev/null
+++ b/src/uart.c
@@ -0,0 +1,74 @@
+#include <avr/io.h>
+#include <stdio.h>
+#include <util/setbaud.h>
+
+/** UART notes
+ * UCSR0A:
+ *  0: MP communication mode
+ *  1: U2X (double trans speed)
+ *  2: USART parity error
+ *  3: Data overrun (udr0 not read before next frame)
+ *  4: Frame error
+ *  5: Data register empty (new data can be transmitted)
+ *  6: USART transmit complete
+ *  7: USART recieve complete
+ * ____________________________________________________________
+ * UCSR0B:
+ *  0: transmit data bit 8
+ *  1: recieve data bit 8
+ *  2: USART char size 0 (used with UCSZ01 and UCSZ00 to set data frame size)
+ *  3: Transmitter enable
+ *  4: Reciever  enable
+ *  5: USART data reg empty interrupt table
+ *  6: TX complete int enable
+ *  7: RX complete int enable
+ * ____________________________________________________________
+ * UCSR0C:
+ *  0: Clock polarity (1: falling edge trasmit, recieve rising edge)
+ *  1: USART char size 0
+ *  2: USART char size 1
+ *  3: USART stop bit select (1: 1 stop bit, 0: 2 stop bits)
+ *  4: USART parity mode (00: async, 01: sync)
+ *  5: USART Parity mode (02: master SPI)
+ *  6: USART mode select (00: async 01: sync)
+ *  7: USART mode select (02: master SPI)
+ * ____________________________________________________________
+ * UBRR0(H,L): baudrates
+ *
+ **/
+
+//TODO replace with static void and just use high level functions?
+void uart_sendbyte(uint8_t byte) { 
+  if(byte == '\n') uart_sendbyte('\r');
+  loop_until_bit_is_set(UCSR0A, UDRE0); 
+  UDR0 = byte; 
+}
+
+//TODO replace with static void and just use high level functions?
+uint8_t uart_recvbyte() {
+  loop_until_bit_is_set(UCSR0A, RXC0);
+  return UDR0;
+}
+
+void uart_init() {
+  //set baud rate
+  UBRR0H = UBRRH_VALUE;
+  UBRR0L = UBRRL_VALUE;
+
+
+/**
+TODO figure out why USE_2X is enable when it shoudn't be
+   //set baud rate
+#ifdef USE_2X //is set by header
+  UCSR0A |= _BV(U2X0);
+#else
+  UCSR0A &= ~(_BV(U2X0));
+#endif
+**/ 
+
+  UCSR0A &= ~(_BV(U2X0));
+
+  UCSR0C = ((_BV(UCSZ01)) | _BV(UCSZ00)); // set 8 bit char size, yes the '=' is intentional
+  UCSR0B = (_BV(RXEN0) | _BV(TXEN0));
+
+}