code/modbus.h

@@ -52,7 +52,7 @@ THE POSSIBILITY OF SUCH DAMAGE.
 
 /* define baudrate of modbus */
 #ifndef BAUD
-#define BAUD 115200L
+#define BAUD 38400L
 #endif
 
 /*

code/uart.c

@@ -0,0 +1,52 @@
+#include <avr/io.h>
+#include "uart.h"
+
+static int uart_putchar(char c, FILE *stream);
+
+FILE uart_output = FDEV_SETUP_STREAM(uart_putchar, NULL, _FDEV_SETUP_WRITE);
+
+void uart_init()
+{
+    DDRD |= 1 << 1; // TX
+    UART_BAUD_REGH  = (BAUDRATE>>8);
+    UART_BAUD_REGL  = BAUDRATE;               // set baud rate
+
+    UART_CTRL_REGB |= (1<<UART_TXEN_BM)
+                     //|(1<<UART_RXEN_BM)
+                     |(1<<UART_RXCIE_BM);     // enable receiver and transmitter
+
+    UART_CTRL_REGC |= (1<<UART_URSEL_BM)
+                     |(1<<UART_UCSZ0_BM)
+                     |(1<<UART_UCSZ1_BM);             // 8bit data format
+
+    stdout = &uart_output;
+}
+
+static int uart_putchar(char c, FILE *stream) {
+    if (c == '\n') {
+        uart_putchar('\r', stream);
+    }
+    loop_until_bit_is_set(UART_CTRL_REGA, UART_UDRE_BM);
+    UART_DATA_REG = c;
+    return 0;
+}
+
+void read_sync(char buffer[], uint8_t buffersize, uint8_t * bufferindex){
+    for(int i=0; i < buffersize; i++){
+        buffer[i]=0;
+    }
+    *bufferindex=0;
+
+    char input;
+    do{
+        while ((UART_CTRL_REGA & (1 << UART_RXC_BM)) == 0);
+        input = UART_DATA_REG;
+
+        putchar(input); //echo
+        buffer[*bufferindex]=input;
+        *bufferindex=*bufferindex+1;
+    }while(!(input == '\n' || input == '\r'));
+    buffer[*bufferindex]=0;
+    putchar('\n');
+}
+

code/uart.h

@@ -0,0 +1,37 @@
+#ifndef _UART_H_
+#define _UART_H_
+
+#include <stdio.h>
+
+#define BAUD 9600 
+#define BAUDRATE ((F_CPU)/(BAUD*16UL)-1)
+
+#define UART_BAUD_REGH UBRR0H
+#define UART_BAUD_REGL UBRR0L
+
+#define UART_CTRL_REGA UCSR0A
+#define UART_CTRL_REGB UCSR0B
+#define UART_CTRL_REGC UCSR0C
+
+// UCSRA
+#define UART_UDRE_BM UDRE0
+#define UART_RXC_BM RXC0
+
+// UCSRB
+#define UART_TXEN_BM TXEN0
+#define UART_RXEN_BM RXEN0
+#define UART_RXCIE_BM RXCIE0
+
+// UCSRC
+#define UART_URSEL_BM 0 /* only for old atmega */
+#define UART_UCSZ0_BM UCSZ00
+#define UART_UCSZ1_BM UCSZ01
+
+#define UART_DATA_REG UDR0
+
+void uart_init (void);
+void read_sync(char buffer[], uint8_t buffersize, uint8_t * bufferindex);
+
+#endif
+
+