From 5e24f508fab7e8f0f7a55fd7135dded391556f8f Mon Sep 17 00:00:00 2001
From: Eggert Jung <eggert.s.jung@wischhof13.de>
Date: Thu, 28 Nov 2019 19:50:17 +0100
Subject: [PATCH] initial commit

---
 example.c |  8 ++++++++
 makefile  | 40 ++++++++++++++++++++++++++++++++++++++++
 uart.c    | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 uart.h    | 37 +++++++++++++++++++++++++++++++++++++
 4 files changed, 138 insertions(+)
 create mode 100644 example.c
 create mode 100644 makefile
 create mode 100644 uart.c
 create mode 100644 uart.h

diff --git a/example.c b/example.c
new file mode 100644
index 0000000..b7cce67
--- /dev/null
+++ b/example.c
@@ -0,0 +1,8 @@
+#include <avr/io.h>
+#include "uart.h"
+
+int main(void){
+    uart_init();
+    printf("Moin!\n\r");
+    while(1);
+}
diff --git a/makefile b/makefile
new file mode 100644
index 0000000..3ac4add
--- /dev/null
+++ b/makefile
@@ -0,0 +1,40 @@
+TARGET  = example
+FILES   = example uart
+MCU     = atmega328p 
+PROGC	= m328pb
+CC      = avr-gcc
+TOOL    = usbasp
+
+BUILDDIR = build
+
+DEFINES = -DF_CPU=16000000UL
+ 
+CFLAGS  =-mmcu=$(MCU) -O2 -Wall $(DEFINES) -std=c99 -ffunction-sections -fdata-sections
+LDFLAGS =-mmcu=$(MCU) -Wl,--gc-sections
+
+LDFILES = $(foreach FILE,$(FILES),$(BUILDDIR)/$(FILE).o)
+
+all: clean $(BUILDDIR)/$(TARGET).elf
+
+$(BUILDDIR)/%.o: %.c
+	@mkdir -p $(BUILDDIR)
+	$(CC) $(CFLAGS) -c $< -o $(BUILDDIR)/$*.o
+
+$(BUILDDIR)/$(TARGET).elf: $(LDFILES)
+	mkdir -p $(BUILDDIR)
+	$(CC) $(LDFLAGS) $(LDFILES) -o $(BUILDDIR)/$(TARGET).elf
+
+$(BUILDDIR)/$(TARGET).hex : $(BUILDDIR)/$(TARGET).elf
+	 avr-objcopy -j .data -j .text -O ihex $< $@
+
+fuse: 
+	avrdude -p $(PROGC) -c $(TOOL) -U lfuse:w:0xE8:m -U hfuse:w:0xD1:m
+
+load: $(BUILDDIR)/$(TARGET).hex
+	avrdude -p $(PROGC) -c $(TOOL) -U flash:w:$(BUILDDIR)/$(TARGET).hex -v -B 2
+	
+size: $(BUILDDIR)/$(TARGET).elf
+	avr-size -C --mcu=$(MCU) $(BUILDDIR)/$(TARGET).elf
+
+clean:
+	rm -rf $(BUILDDIR)
diff --git a/uart.c b/uart.c
new file mode 100644
index 0000000..195e9e7
--- /dev/null
+++ b/uart.c
@@ -0,0 +1,53 @@
+#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');
+}
+
+
diff --git a/uart.h b/uart.h
new file mode 100644
index 0000000..21e6e88
--- /dev/null
+++ b/uart.h
@@ -0,0 +1,37 @@
+#ifndef _UART_H_
+#define _UART_H_
+
+#include <stdio.h>
+
+#define BAUD 38400 
+#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
+
+