Fix uart3_init comment

.gitignore

@@ -1,6 +1,9 @@
 # Build artefacts
 bin/*
 
+# astyle formatter preserved files
+*.orig
+
 #
 # Templates from https://github.com/github/gitignore
 #

Makefile

@@ -0,0 +1,86 @@
+###############################################################################
+#
+# Simple Makefile for Arduino MEGA 2560 C projects
+#
+###############################################################################
+
+CC = avr-gcc
+OBJCOPY = avr-objcopy
+AVRDUDE = avrdude
+CODE_FORMATTER = tooling/format-code.sh
+
+BOARD = atmega2560
+
+# Use shell command export to define it
+# Example: export ARDUINO=/dev/ttyACM0
+DEVICE = $(ARDUINO)
+
+# Build artifacts
+BINDIR = bin
+TARGET = $(BINDIR)/$(BOARD)-user-code.ihx
+ELF = $(BINDIR)/$(BOARD)-user-code.elf
+
+# Source files. wildard "uses" all .c files in src directory
+SRCDIR = src
+SRC = $(wildcard $(SRCDIR)/*.c)
+
+# Define object files from .c files defined above
+OBJ=$(SRC:.c=.o)
+
+# Compiler flags
+# Note that those beginning with -D are acctually pre-processor macros
+# -Wall ... -Wfatal-errors All possible warning options
+# -Os Optimize code. The special option -Os is meant to turn on all -O2
+# optimizations that are not expected to increase code size.
+# -std=c11 use C11 standard
+CFLAGS =	-Wall \
+			-Wextra \
+			-Wpedantic \
+			-Wformat \
+			-pedantic-errors \
+			-Werror \
+			-Wfatal-errors \
+			-Os \
+			-mmcu=$(BOARD) \
+			-DF_CPU=16000000UL \
+			-DGIT_DESCR=\"$(shell git describe --abbrev=6 --dirty --always --tags --long)\" \
+			-std=c11
+
+# Linker flags
+LDFLAGS = -mmcu=$(BOARD)
+
+OBJCOPYARGS =	-O ihex \
+				-R .eeprom
+
+# FIXME Find out why some Arduinos require -D to write code
+AVRDUDEARGS =	-p $(BOARD) \
+				-c wiring \
+				-F \
+				-P $(DEVICE) \
+				-b 115200 \
+				-V \
+				-D
+
+all: $(ELF) $(TARGET)
+
+%.o : %.c
+	$(CC) -c $(CFLAGS) -o $*.o $<
+
+$(ELF): $(OBJ)
+	$(CC) $(LDFLAGS) $^ -o $@
+
+$(TARGET):
+	$(OBJCOPY) $(OBJCOPYARGS) $(ELF) $(TARGET)
+
+clean:
+#Do not remove .placeholder in BINDIR
+	find $(BINDIR) -type f -not -name '.placeholder' -print0 | xargs -0 rm -f --
+	rm -f $(SRCDIR)/*.o
+
+install:
+	$(AVRDUDE) $(AVRDUDEARGS) -U flash:w:$(TARGET)
+
+format:
+	$(CODE_FORMATTER) $(SRC)
+
+.PHONY: clean install format

doc/Arduino-Mega-USB-UART-wiring.markdown

@@ -0,0 +1,17 @@
+# Arduino Mega USB UART converter wiring
+
+## Introduction
+
+This wiring schema uses only Tx from Arduino and is suitable to be used as standard error console.
+
+## Wiring illustration
+
+![Arduino Mega USB UART wiring.png](Arduino-Mega-USB-UART-wiring.png)
+
+## Wiring table
+
+| Signal | ATMega2560 port and pin | Arduino Mega 2560 pin | USB UART converter pin |
+| --- | --- | --- | --- |
+| Ground (GND) | - | GND | GND |
+| Transmit data  from Arduino (TxD) | PORTJ 1 (TXD3) | 14 (TX3) | TxD |
+

src/main.c

@@ -1,18 +1,47 @@
+#include <stdio.h>
 #include <avr/io.h>
 #include <util/delay.h>
+#define __ASSERT_USE_STDERR
+#include <assert.h>
+#include "uart.h"
 
-#define BLINK_DELAY_MS  1000
+#define BLINK_DELAY_MS 100
 
 int main (void)
 {
-    /*  set pin 25 of PORTB for output*/
+    /* set pin 3 of PORTA for output*/
     DDRA |= _BV(DDA3);
-    while(1) {
+    /* Init error console as stderr in UART3 and print user code info */
-        /*  set pin 25 high to turn led on  */
+    uart3_init();
+    stderr = &uart3_out;
+    fprintf(stderr, "Version: %s built on: %s %s\n",
+            GIT_DESCR, __DATE__, __TIME__);
+    fprintf(stderr, "avr-libc version: %s\n", __AVR_LIBC_VERSION_STRING__);
+    /*End UART3 init and info print */
+    /* Test assert - REMOVE IN FUTURE LABS */
+    char *array;
+    uint32_t i = 1;
+    extern int __heap_start, *__brkval;
+    int v;
+    array = malloc( i * sizeof(char));
+    assert(array);
+    /* End test assert */
+
+    while (1) {
+        /* set pin 3 high to turn led on */
         PORTA |= _BV(PORTA3);
         _delay_ms(BLINK_DELAY_MS);
-        /*  set pin 25 low to turn led off */
+        /* Test assert - REMOVE IN FUTURE LABS */
-        PORTA   &=  ~_BV(PORTA3);
+        /* Increase memory allocated for array by 100 chars
+         * until we have eaten it all and print space between Stack and Heap.
+         * Thats how assert works in run-time */
+        array = realloc( array, (i++ * 100) * sizeof(char));
+        fprintf(stderr, "%d ",
+                (int) &v - (__brkval == 0 ? (int) &__heap_start : (int) __brkval));
+        assert(array);
+        /* End test assert */
+        /* set pin 3 low to turn led off */
+        PORTA &= ~_BV(PORTA3);
         _delay_ms(BLINK_DELAY_MS);
     }
 }

src/uart.c

@@ -0,0 +1,72 @@
+#include <avr/io.h>
+#include <stdio.h>
+
+#ifndef F_CPU
+#define F_CPU 16000000UL
+#endif
+
+#ifndef BAUD
+#define BAUD 9600
+#endif
+#include <util/setbaud.h>
+
+/* http://www.cs.mun.ca/~rod/Winter2007/4723/notes/serial/serial.html */
+
+void uart0_init(void)
+{
+    UBRR0H = UBRRH_VALUE;
+    UBRR0L = UBRRL_VALUE;
+#if USE_2X
+    UCSR0A |= _BV(U2X0);
+#else
+    UCSR0A &= ~(_BV(U2X0));
+#endif
+    UCSR0C = _BV(UCSZ01) | _BV(UCSZ00); /* 8-bit data */
+    UCSR0B = _BV(RXEN0) | _BV(TXEN0);   /* Enable RX and TX */
+}
+
+void uart3_init(void)
+{
+    UBRR3H = UBRRH_VALUE;
+    UBRR3L = UBRRL_VALUE;
+#if USE_2X
+    UCSR3A |= _BV(U2X3);
+#else
+    UCSR3A &= ~(_BV(U2X3));
+#endif
+    UCSR3C = _BV(UCSZ31) | _BV(UCSZ30); /* 8-bit data */
+    UCSR3B = _BV(TXEN3);   /* Enable TX */
+}
+
+int uart0_putchar(char c, FILE *stream)
+{
+    (void) stream;
+
+    if (c == '\n') {
+        uart0_putchar('\r', stream);
+    }
+
+    loop_until_bit_is_set(UCSR0A, UDRE0);
+    UDR0 = c;
+    return 0;
+}
+
+int uart3_putchar(char c, FILE *stream)
+{
+    (void) stream;
+
+    if (c == '\n') {
+        uart3_putchar('\r', stream);
+    }
+
+    loop_until_bit_is_set(UCSR3A, UDRE3);
+    UDR3 = c;
+    return 0;
+}
+
+int uart0_getchar(FILE *stream)
+{
+    (void) stream;
+    loop_until_bit_is_set(UCSR0A, RXC0);
+    return UDR0;
+}

src/uart.h

@@ -0,0 +1,12 @@
+int uart0_putchar(char c, FILE *stream);
+int uart0_getchar(FILE *stream);
+
+int uart3_putchar(char c, FILE *stream);
+
+void uart0_init(void);
+void uart3_init(void);
+
+/* http://www.ermicro.com/blog/?p=325 */
+
+FILE uart0_io = FDEV_SETUP_STREAM(uart0_putchar, uart0_getchar, _FDEV_SETUP_RW);
+FILE uart3_out = FDEV_SETUP_STREAM(uart3_putchar, NULL, _FDEV_SETUP_WRITE);

tooling/format-code.sh

@@ -0,0 +1,48 @@
+#!/bin/bash
+
+# Simple script for code formatting in 1tbs
+# See http://astyle.sourceforge.net/astyle.html for syntax and defaults
+
+MINPARAMS=1
+ORIG_SUFFIX=orig
+
+if [ $# -lt "$MINPARAMS" ]
+then
+    echo "This script needs C source files passed as arguments"
+    echo "USAGE: format-code.sh src/main.c src/somecode.c ..."
+    exit 1
+fi
+
+# 
+for FILE in "$@"
+do
+    RESULT="$(astyle    --style=1tbs \
+                        --indent-col1-comments \
+                        --break-blocks \
+                        --pad-oper \
+                        --pad-header \
+                        --delete-empty-lines \
+                        --add-brackets \
+                        --convert-tabs \
+                        --max-code-length=80 \
+                        --break-after-logical \
+                        --mode=c \
+                        --suffix=.$ORIG_SUFFIX \
+                        --lineend=linux \
+                        $FILE)"
+
+    # if file unchanged print unchanged result message
+    if [[ "$RESULT" = Unchanged* ]]
+    then
+        echo "$RESULT"
+    fi
+
+    # if file formatted print result and renamed file name
+    if [[ "$RESULT" = Formatted* ]]
+    then
+        echo "$RESULT"
+        echo "Original code was preserved in file $FILE.$ORIG_SUFFIX"
+    fi
+done
+
+exit 0