Style fixes and added some comments

Makefile

@@ -8,6 +8,7 @@ CC = avr-gcc
 OBJCOPY = avr-objcopy
 AVRDUDE = avrdude
 CODE_FORMATTER = tooling/format-code.sh
+AVRSIZE = avr-size
 
 BOARD = atmega2560
 
@@ -42,13 +43,19 @@ CFLAGS =	-Wall \
 			-Werror \
 			-Wfatal-errors \
 			-Os \
+			-flto \
+			-fdata-sections \
+			-ffunction-sections \
 			-mmcu=$(BOARD) \
 			-DF_CPU=16000000UL \
 			-DGIT_DESCR=\"$(shell git describe --abbrev=6 --dirty --always --tags --long)\" \
+			-ffreestanding \
 			-std=c11
 
 # Linker flags
-LDFLAGS = -mmcu=$(BOARD)
+LDFLAGS =	-mmcu=$(BOARD) \
+			-flto \
+			-Wl,-gc-sections
 
 OBJCOPYARGS =	-O ihex \
 				-R .eeprom
@@ -62,6 +69,9 @@ AVRDUDEARGS =	-p $(BOARD) \
 				-V \
 				-D
 
+AVRSIZEARGS =	-C \
+				--mcu=$(BOARD)
+
 all: $(ELF) $(TARGET)
 
 %.o : %.c
@@ -80,9 +90,19 @@ clean:
 	rm -fr $(BUILD_LIBS_DIR)/*/*.o
 
 install:
+	@if [ ! -c "$(ARDUINO)" ]; then \
+		echo -e "\n\nEnvironment variable ARDUINO is \"$(ARDUINO)\" and that is invalid."\
+				"\nDid you do \"export ARDUINO=/dev/ttyACM0\" before running make install?"\
+				"\nAlso make sure that ARDUINO env var points to a valid tty device\n\n"; \
+		exit 1;\
+	fi
+	
 	$(AVRDUDE) $(AVRDUDEARGS) -U flash:w:$(TARGET)
 
 format:
-	$(CODE_FORMATTER) $(SRC)
+	$(CODE_FORMATTER) $(SRCDIR)/*.c
 
-.PHONY: clean install format
+size:
+	$(AVRSIZE) $(AVRSIZEARGS) $(ELF)
+
+.PHONY: clean install format size

doc/arduino-mega-lcd1602-keypad-shield-wiring.markdown

@@ -10,9 +10,21 @@ This shield consists of three logical parts:
 
 <div class=pagebreak></div>
 
+## Connection to Arduino Mega
+
+Following illustration shows how shield is connected to Arduino mega board.
+
+![arduino-mega-lcd1602-keypad-shield-placement.png](arduino-mega-lcd1602-keypad-shield-placement.png)
+
+Image source: [sainsmart.com](http://www.sainsmart.com/media/catalog/product/2/_/2_16_6.jpg)
+
+Additional installation details and tutorials can be found with help of keywords [Arduino 1602 lcd keypad shield tutorial](https://www.google.ee/webhp?q=Arduino+1602+lcd+keypad+shield+tutorial).
+
+<div class=pagebreak></div>
+
 ## Wiring illustration
 
-![Arduino Mega LCD1602 Keypad shield wiring LCD part.png](Arduino-Mega-LCD1602-keypad-shield-wiring.png)
+![arduino-mega-lcd1602-keypad-shield-wiring.png](arduino-mega-lcd1602-keypad-shield-wiring.png)
 
 Author: [Lauri Võsandi](http://lauri.võsandi.com/arduino/lcd1602-key-shield.html#hd44780)
 

doc/arduino-mega-usb-uart-wiring.markdown

@@ -6,12 +6,12 @@ This wiring schema uses only Tx from Arduino and is suitable to be used as stand
 
 ## Wiring illustration
 
-![Arduino Mega USB UART wiring.png](Arduino-Mega-USB-UART-wiring.png)
+![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 | GND |
-| Transmit data  from Arduino (TxD) | PORTJ pin 1 (TXD3) | Digital pin 14 (TX3) | TxD |
+| Transmit data  from Arduino (TxD) | PORTJ pin 1 (TXD3) | Digital pin 14 (TX3) | RxD |
 

lib/andygock_avr-uart/LICENSE.txt

@@ -0,0 +1,11 @@
+Copyright (C) 2012 Andy Gock
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.

lib/andygock_avr-uart/README.md

@@ -0,0 +1,56 @@
+avr-uart
+========
+
+An interrupt driven UART Library for 8-bit AVR microcontrollers
+
+Maintained by Andy Gock
+
+https://github.com/andygock/avr-uart
+
+Derived from original library by Peter Fleury
+
+Interrupt UART library using the built-in UART with transmit and receive circular buffers.
+
+An interrupt is generated when the UART has finished transmitting or
+receiving a byte. The interrupt handling routines use circular buffers
+for buffering received and transmitted data.
+
+## Setting up
+
+The `UART_RXn_BUFFER_SIZE` and `UART_TXn_BUFFER_SIZE` constants define
+the size of the circular buffers in bytes. Note that these constants must be a power of 2.
+You may need to adapt this constants to your target and your application by adding to your
+compiler options:
+
+	-DUART_RXn_BUFFER_SIZE=nn -DUART_TXn_BUFFER_SIZE=nn
+ 
+`RXn` and `TXn` refer to UART number, for UART3 with 128 byte buffers, add:
+
+	-DUART_RX3_BUFFER_SIZE=128 -DUART_TX3_BUFFER_SIZE=128
+
+UART0 is always enabled by default, to enable the other available UARTs, add the following
+to your compiler options (or symbol options), for the relevant USART number:
+
+	-DUSART1_ENABLED -DUSART2_ENABLED -DUSART3_ENABLED
+ 
+To enable large buffer support (over 256 bytes, up to 2^16 bytes) use:
+
+	-DUSARTn_LARGE_BUFFER
+	
+Where n = USART number.
+
+Supports AVR devices with up to 4 hardware USARTs.
+
+## Documentation
+
+Doxygen based documentation will be coming soon.
+
+## Notes
+
+### Buffer overflow behaviour
+
+When the RX circular buffer is full, and it receives further data from the UART, a buffer overflow condition occurs. Any new data is dropped. The RX buffer must be read before any more incoming data from the UART is placed into the RX buffer.
+
+If the TX buffer is full, and new data is sent to it using one of the `uartN_put*()` functions, this function will loop and wait until the buffer is not full any more. It is important to make sure you have not disabled your UART transmit interrupts (`TXEN*`) elsewhere in your application (e.g with `cli()`) before calling the `uartN_put*()` functions, as the application will lock up. The UART interrupts are automatically enabled when you use the `uartN_init()` functions. This is probably not the idea behaviour, I'll probably fix this some time.
+
+For now, make sure `TXEN*` interrupts are enabled when calling `uartN_put*()` functions. This should not be an issue unless you have code elsewhere purposely turning it off.

lib/andygock_avr-uart/uart.h

@@ -0,0 +1,415 @@
+#ifndef UART_H
+#define UART_H
+
+
+/************************************************************************
+Title:    Interrupt UART library with receive/transmit circular buffers
+Author:   Andy Gock
+Software: AVR-GCC 4.1, AVR Libc 1.4
+Hardware: any AVR with built-in UART, tested on AT90S8515 & ATmega8 at 4 Mhz
+License:  GNU General Public License 
+Usage:    see Doxygen manual
+
+Based on original library by Peter Fluery, Tim Sharpe, Nicholas Zambetti.
+
+https://github.com/andygock/avr-uart
+
+LICENSE:
+	Copyright (C) 2012 Andy Gock
+
+	This program is free software; you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation; either version 2 of the License, or
+	any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+LICENSE:
+    Copyright (C) 2006 Peter Fleury
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+    
+************************************************************************/
+
+/************************************************************************
+uart_available, uart_flush, uart1_available, and uart1_flush functions
+were adapted from the Arduino HardwareSerial.h library by Tim Sharpe on 
+11 Jan 2009.  The license info for HardwareSerial.h is as follows:
+
+  HardwareSerial.h - Hardware serial library for Wiring
+  Copyright (c) 2006 Nicholas Zambetti.  All right reserved.
+
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with this library; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+************************************************************************/
+
+/************************************************************************
+Changelog for modifications made by Tim Sharpe, starting with the current
+  library version on his Web site as of 05/01/2009. 
+
+Date        Description
+=========================================================================
+05/12/2009  Added Arduino-style available() and flush() functions for both
+			supported UARTs.  Really wanted to keep them out of the library, so
+			that it would be as close as possible to Peter Fleury's original
+			library, but has scoping issues accessing internal variables from
+			another program.  Go C!
+
+************************************************************************/
+
+/** 
+ *  @defgroup avr-uart UART Library
+ *  @code #include <uart.h> @endcode
+ * 
+ *  @brief Interrupt UART library using the built-in UART with transmit and receive circular buffers. 
+ *
+ *  This library can be used to transmit and receive data through the built in UART. 
+ *
+ *  An interrupt is generated when the UART has finished transmitting or
+ *  receiving a byte. The interrupt handling routines use circular buffers
+ *  for buffering received and transmitted data.
+ *
+ *  The UART_RXn_BUFFER_SIZE and UART_TXn_BUFFER_SIZE constants define
+ *  the size of the circular buffers in bytes. Note that these constants must be a power of 2.
+ *
+ *  You need to define these buffer sizes in uart.h
+ *
+ *  @note Based on Atmel Application Note AVR306
+ *  @author Andy Gock <andy@gock.net>
+ *  @note Based on original library by Peter Fleury and Tim Sharpe.
+ */
+ 
+/**@{*/
+#include <stdint.h>
+#include <avr/io.h>
+
+#if (__GNUC__ * 100 + __GNUC_MINOR__) < 304
+#error "This library requires AVR-GCC 3.4 or later, update to newer AVR-GCC compiler !"
+#endif
+
+/*
+ * constants and macros
+ */
+
+/* Enable USART 1, 2, 3 as required */
+#define USART0_ENABLED
+//#define USART1_ENABLED
+//#define USART2_ENABLED 
+#define USART3_ENABLED
+
+/* Set size of receive and transmit buffers */
+
+#ifndef UART_RX0_BUFFER_SIZE
+	#define UART_RX0_BUFFER_SIZE 128 /**< Size of the circular receive buffer, must be power of 2 */
+#endif
+#ifndef UART_RX1_BUFFER_SIZE
+	#define UART_RX1_BUFFER_SIZE 128 /**< Size of the circular receive buffer, must be power of 2 */
+#endif
+#ifndef UART_RX2_BUFFER_SIZE
+	#define UART_RX2_BUFFER_SIZE 128 /**< Size of the circular receive buffer, must be power of 2 */
+#endif
+#ifndef UART_RX3_BUFFER_SIZE
+	#define UART_RX3_BUFFER_SIZE 128 /**< Size of the circular receive buffer, must be power of 2 */
+#endif
+
+#ifndef UART_TX0_BUFFER_SIZE
+	#define UART_TX0_BUFFER_SIZE 128 /**< Size of the circular transmit buffer, must be power of 2 */
+#endif
+#ifndef UART_TX1_BUFFER_SIZE
+	#define UART_TX1_BUFFER_SIZE 128 /**< Size of the circular transmit buffer, must be power of 2 */
+#endif
+#ifndef UART_TX2_BUFFER_SIZE
+	#define UART_TX2_BUFFER_SIZE 128 /**< Size of the circular transmit buffer, must be power of 2 */
+#endif
+#ifndef UART_TX3_BUFFER_SIZE
+	#define UART_TX3_BUFFER_SIZE 128 /**< Size of the circular transmit buffer, must be power of 2 */
+#endif
+
+/* Check buffer sizes are not too large for 8-bit positioning */
+
+#if (UART_RX0_BUFFER_SIZE > 256 & !defined(USART0_LARGE_BUFFER))
+	#error "Buffer too large, please use -DUSART0_LARGE_BUFFER switch in compiler options"
+#endif
+
+#if (UART_RX1_BUFFER_SIZE > 256 & !defined(USART1_LARGE_BUFFER))
+	#error "Buffer too large, please use -DUSART1_LARGE_BUFFER switch in compiler options"
+#endif
+
+#if (UART_RX2_BUFFER_SIZE > 256 & !defined(USART2_LARGE_BUFFER))
+	#error "Buffer too large, please use -DUSART2_LARGE_BUFFER switch in compiler options"
+#endif
+
+#if (UART_RX3_BUFFER_SIZE > 256 & !defined(USART3_LARGE_BUFFER))
+	#error "Buffer too large, please use -DUSART3_LARGE_BUFFER switch in compiler options"
+#endif
+
+/* Check buffer sizes are not too large for *_LARGE_BUFFER operation (16-bit positioning) */
+
+#if (UART_RX0_BUFFER_SIZE > 65536)
+	#error "Buffer too large, maximum allowed is 65536 bytes"
+#endif
+
+#if (UART_RX1_BUFFER_SIZE > 65536)
+	#error "Buffer too large, maximum allowed is 65536 bytes"
+#endif
+
+#if (UART_RX2_BUFFER_SIZE > 65536)
+	#error "Buffer too large, maximum allowed is 65536 bytes"
+#endif
+
+#if (UART_RX3_BUFFER_SIZE > 65536)
+	#error "Buffer too large, maximum allowed is 65536 bytes"
+#endif
+
+/** @brief  UART Baudrate Expression
+ *  @param  xtalCpu  system clock in Mhz, e.g. 4000000L for 4Mhz          
+ *  @param  baudRate baudrate in bps, e.g. 1200, 2400, 9600     
+ */
+#define UART_BAUD_SELECT(baudRate,xtalCpu) (((xtalCpu)+8UL*(baudRate))/(16UL*(baudRate))-1UL)
+
+/** @brief  UART Baudrate Expression for ATmega double speed mode
+ *  @param  xtalCpu  system clock in Mhz, e.g. 4000000L for 4Mhz           
+ *  @param  baudRate baudrate in bps, e.g. 1200, 2400, 9600     
+ */
+#define UART_BAUD_SELECT_DOUBLE_SPEED(baudRate,xtalCpu) ((((xtalCpu)+4UL*(baudRate))/(8UL*(baudRate))-1)|0x8000)
+
+/* test if the size of the circular buffers fits into SRAM */
+
+#if defined(USART0_ENABLED) && ( (UART_RX0_BUFFER_SIZE+UART_TX0_BUFFER_SIZE) >= (RAMEND-0x60 ) )
+#error "size of UART_RX0_BUFFER_SIZE + UART_TX0_BUFFER_SIZE larger than size of SRAM"
+#endif
+
+#if defined(USART1_ENABLED) && ( (UART_RX1_BUFFER_SIZE+UART_TX1_BUFFER_SIZE) >= (RAMEND-0x60 ) )
+#error "size of UART_RX1_BUFFER_SIZE + UART_TX1_BUFFER_SIZE larger than size of SRAM"
+#endif
+
+#if defined(USART2_ENABLED) && ( (UART_RX2_BUFFER_SIZE+UART_RX2_BUFFER_SIZE) >= (RAMEND-0x60 ) )
+#error "size of UART_RX2_BUFFER_SIZE + UART_TX2_BUFFER_SIZE larger than size of SRAM"
+#endif
+
+#if defined(USART3_ENABLED) && ( (UART_RX3_BUFFER_SIZE+UART_RX3_BUFFER_SIZE) >= (RAMEND-0x60 ) )
+#error "size of UART_RX3_BUFFER_SIZE + UART_TX3_BUFFER_SIZE larger than size of SRAM"
+#endif
+
+/* 
+** high byte error return code of uart_getc()
+*/
+#define UART_FRAME_ERROR      0x0800              /**< Framing Error by UART       */
+#define UART_OVERRUN_ERROR    0x0400              /**< Overrun condition by UART   */
+#define UART_BUFFER_OVERFLOW  0x0200              /**< receive ringbuffer overflow */
+#define UART_NO_DATA          0x0100              /**< no receive data available   */
+
+/* Macros, to allow use of legacy names */
+
+#define uart_init(b)      uart0_init(b)
+#define uart_getc()       uart0_getc()
+#define uart_putc(d)      uart0_putc(d)
+#define uart_puts(s)      uart0_puts(s)
+#define uart_puts_p(s)    uart0_puts_p(s)
+#define uart_available()  uart0_available()
+#define uart_flush()      uart0_flush()
+
+/*
+** function prototypes
+*/
+
+/**
+   @brief   Initialize UART and set baudrate 
+   @param   baudrate Specify baudrate using macro UART_BAUD_SELECT()
+   @return  none
+*/
+extern void uart0_init(uint16_t baudrate);
+
+
+/**
+ *  @brief   Get received byte from ringbuffer
+ *
+ * Returns in the lower byte the received character and in the 
+ * higher byte the last receive error.
+ * UART_NO_DATA is returned when no data is available.
+ *
+ *  @return  lower byte:  received byte from ringbuffer
+ *  @return  higher byte: last receive status
+ *           - \b 0 successfully received data from UART
+ *           - \b UART_NO_DATA           
+ *             <br>no receive data available
+ *           - \b UART_BUFFER_OVERFLOW   
+ *             <br>Receive ringbuffer overflow.
+ *             We are not reading the receive buffer fast enough, 
+ *             one or more received character have been dropped 
+ *           - \b UART_OVERRUN_ERROR     
+ *             <br>Overrun condition by UART.
+ *             A character already present in the UART UDR register was 
+ *             not read by the interrupt handler before the next character arrived,
+ *             one or more received characters have been dropped.
+ *           - \b UART_FRAME_ERROR       
+ *             <br>Framing Error by UART
+ */
+extern uint16_t uart0_getc(void);
+
+/**
+ *  @brief   Peek at next byte in ringbuffer
+ *
+ * Returns the next byte (character) of incoming UART data without removing it from the
+ * internal ring buffer. That is, successive calls to uartN_peek() will return the same
+ * character, as will the next call to uartN_getc().
+ *
+ * UART_NO_DATA is returned when no data is available.
+ *
+ *  @return  lower byte:  next byte in ringbuffer
+ *  @return  higher byte: last receive status
+ *           - \b 0 successfully received data from UART
+ *           - \b UART_NO_DATA           
+ *             <br>no receive data available
+ *           - \b UART_BUFFER_OVERFLOW   
+ *             <br>Receive ringbuffer overflow.
+ *             We are not reading the receive buffer fast enough, 
+ *             one or more received character have been dropped 
+ *           - \b UART_OVERRUN_ERROR     
+ *             <br>Overrun condition by UART.
+ *             A character already present in the UART UDR register was 
+ *             not read by the interrupt handler before the next character arrived,
+ *             one or more received characters have been dropped.
+ *           - \b UART_FRAME_ERROR       
+ *             <br>Framing Error by UART
+ */
+extern uint16_t uart0_peek(void);
+
+/**
+ *  @brief   Put byte to ringbuffer for transmitting via UART
+ *  @param   data byte to be transmitted
+ *  @return  none
+ */
+extern void uart0_putc(uint8_t data);
+
+
+/**
+ *  @brief   Put string to ringbuffer for transmitting via UART
+ *
+ *  The string is buffered by the uart library in a circular buffer
+ *  and one character at a time is transmitted to the UART using interrupts.
+ *  Blocks if it can not write the whole string into the circular buffer.
+ * 
+ *  @param   s string to be transmitted
+ *  @return  none
+ */
+extern void uart0_puts(const char *s );
+
+
+/**
+ * @brief    Put string from program memory to ringbuffer for transmitting via UART.
+ *
+ * The string is buffered by the uart library in a circular buffer
+ * and one character at a time is transmitted to the UART using interrupts.
+ * Blocks if it can not write the whole string into the circular buffer.
+ *
+ * @param    s program memory string to be transmitted
+ * @return   none
+ * @see      uart0_puts_P
+ */
+extern void uart0_puts_p(const char *s );
+
+/**
+ * @brief    Macro to automatically put a string constant into program memory
+ * \param    __s string in program memory
+ */
+#define uart_puts_P(__s)       uart0_puts_p(PSTR(__s))
+#define uart0_puts_P(__s)      uart0_puts_p(PSTR(__s))
+
+/**
+ *  @brief   Return number of bytes waiting in the receive buffer
+ *  @return  bytes waiting in the receive buffer
+ */
+extern uint16_t uart0_available(void);
+
+/**
+ *  @brief   Flush bytes waiting in receive buffer
+ */
+extern void uart0_flush(void);
+
+
+/** @brief  Initialize USART1 (only available on selected ATmegas) @see uart_init */
+extern void uart1_init(uint16_t baudrate);
+/** @brief  Get received byte of USART1 from ringbuffer. (only available on selected ATmega) @see uart_getc */
+extern uint16_t uart1_getc(void);
+/** @brief  Peek at next byte in USART1 ringbuffer */
+extern uint16_t uart1_peek(void);
+/** @brief  Put byte to ringbuffer for transmitting via USART1 (only available on selected ATmega) @see uart_putc */
+extern void uart1_putc(uint8_t data);
+/** @brief  Put string to ringbuffer for transmitting via USART1 (only available on selected ATmega) @see uart_puts */
+extern void uart1_puts(const char *s );
+/** @brief  Put string from program memory to ringbuffer for transmitting via USART1 (only available on selected ATmega) @see uart_puts_p */
+extern void uart1_puts_p(const char *s );
+/** @brief  Macro to automatically put a string constant into program memory */
+#define uart1_puts_P(__s)       uart1_puts_p(PSTR(__s))
+/** @brief   Return number of bytes waiting in the receive buffer */
+extern uint16_t uart1_available(void);
+/** @brief   Flush bytes waiting in receive buffer */
+extern void uart1_flush(void);
+
+
+/** @brief  Initialize USART2 (only available on selected ATmegas) @see uart_init */
+extern void uart2_init(uint16_t baudrate);
+/** @brief  Get received byte of USART2 from ringbuffer. (only available on selected ATmega) @see uart_getc */
+extern uint16_t uart2_getc(void);
+/** @brief  Peek at next byte in USART2 ringbuffer */
+extern uint16_t uart2_peek(void);
+/** @brief  Put byte to ringbuffer for transmitting via USART2 (only available on selected ATmega) @see uart_putc */
+extern void uart2_putc(uint8_t data);
+/** @brief  Put string to ringbuffer for transmitting via USART2 (only available on selected ATmega) @see uart_puts */
+extern void uart2_puts(const char *s );
+/** @brief  Put string from program memory to ringbuffer for transmitting via USART2 (only available on selected ATmega) @see uart_puts_p */
+extern void uart2_puts_p(const char *s );
+/** @brief  Macro to automatically put a string constant into program memory */
+#define uart2_puts_P(__s)       uart2_puts_p(PSTR(__s))
+/** @brief   Return number of bytes waiting in the receive buffer */
+extern uint16_t uart2_available(void);
+/** @brief   Flush bytes waiting in receive buffer */
+extern void uart2_flush(void);
+
+
+/** @brief  Initialize USART3 (only available on selected ATmegas) @see uart_init */
+extern void uart3_init(uint16_t baudrate);
+/** @brief  Get received byte of USART3 from ringbuffer. (only available on selected ATmega) @see uart_getc */
+extern uint16_t uart3_getc(void);
+/** @brief  Peek at next byte in USART3 ringbuffer */
+extern uint16_t uart3_peek(void);
+/** @brief  Put byte to ringbuffer for transmitting via USART3 (only available on selected ATmega) @see uart_putc */
+extern void uart3_putc(uint8_t data);
+/** @brief  Put string to ringbuffer for transmitting via USART3 (only available on selected ATmega) @see uart_puts */
+extern void uart3_puts(const char *s );
+/** @brief  Put string from program memory to ringbuffer for transmitting via USART3 (only available on selected ATmega) @see uart_puts_p */
+extern void uart3_puts_p(const char *s );
+/** @brief  Macro to automatically put a string constant into program memory */
+#define uart3_puts_P(__s)       uart3_puts_p(PSTR(__s))
+/** @brief   Return number of bytes waiting in the receive buffer */
+extern uint16_t uart3_available(void);
+/** @brief   Flush bytes waiting in receive buffer */
+extern void uart3_flush(void);
+
+/**@}*/
+
+#endif // UART_H 
+

src/hmi_msg.h

@@ -2,17 +2,18 @@
 #ifndef _HMI_MSG_H_
 #define _HMI_MSG_H_
 
-const char PROG_VERSION[]  PROGMEM = "Version: %s built on: %s %s\n";
-const char LIBC_VERSION[]  PROGMEM = "avr-libc version: %s\n";
-const char STUD_NAME[]     PROGMEM = "Arti Zirk";
-const char GET_MONTH_MSG[] PROGMEM = "Enter Month name first letter >";
-const char ENG_MONTH[6][9] PROGMEM = {
-                                        "January",
-                                        "February",
-                                        "March",
-                                        "April",
-                                        "May",
-                                        "June",
-                                      };
+#define PROG_VERSION "Version: %S built on: %S %S"
+#define LIBC_VERSION "avr-libc version: %S"
+#define STUD_NAME "Arti Zirk"
+#define GET_MONTH_MSG "Enter Month name first letter >"
+#define UPTIME_MSG "Uptime: %lu s"
 
+const char m1[] PROGMEM = "January";
+const char m2[] PROGMEM = "February";
+const char m3[] PROGMEM = "March";
+const char m4[] PROGMEM = "April";
+const char m5[] PROGMEM = "May";
+const char m6[] PROGMEM = "June";
+
+PGM_P const months[] PROGMEM = {m1,m2,m3,m4,m5,m6};
 #endif /* _HMI_MSG_H_ */

src/main.c

@@ -1,69 +1,128 @@
 #include <stdio.h>
 #include <string.h>
+#include <time.h>
 #include <avr/io.h>
+#include <avr/interrupt.h>
 #include <avr/pgmspace.h>
 #include <util/delay.h>
 #include "hmi_msg.h"
-#include "uart.h"
+#include "../lib/andygock_avr-uart/uart.h"
+#include "uart_wrap.h"
 #include "print_helper.h"
 #include "../lib/hd44780_111/hd44780.h"
 
-#define BLINK_DELAY_MS 100
+#define BAUDRATE 9600
 
-int main (void)
+// For configuring arduino mega pin 25
+#define LED_INIT DDRA |= _BV(DDA3);
+#define LED_TOGGLE PORTA ^= _BV(PORTA3)
+
+static inline void init_system_clock(void)
 {
-    /* Init */
-    DDRA |= _BV(DDA3);
-    uart0_init();
-    uart3_init();
+    TCCR5A = 0; // Clear control register A
+    TCCR5B = 0; // Clear control register B
+    TCCR5B |= _BV(WGM52) | _BV(CS52); // CTC and fCPU/256
+    OCR5A = 62549; // 1 s
+    TIMSK5 |= _BV(OCIE5A); // Output Compare A Match Interrupt Enable
+}
+
+static inline void init_hw (void)
+{
+    // IO init
+    /// Set arduino pin 25 as output
+    LED_INIT;
+
+    // System clock
+    init_system_clock();
+
+    // UART init
+    uart0_init(UART_BAUD_SELECT(BAUDRATE, F_CPU));
+    uart3_init(UART_BAUD_SELECT(BAUDRATE, F_CPU));
     stdout = stdin = &uart0_io;
     stderr = &uart3_out;
+
+    // LCD init
     lcd_init();
     lcd_clrscr();
-    /* End init */
 
-    /* Print version info to stderr */
-    fprintf_P(stderr, PROG_VERSION, GIT_DESCR, __DATE__, __TIME__);
-    fprintf_P(stderr, LIBC_VERSION, __AVR_LIBC_VERSION_STRING__);
-    /* End version print */
+    // Enable interupts
+    sei();
+}
 
-    fprintf_P(stdout, STUD_NAME);
-    fputc('\n', stdout); /* Add a new line to the uart printout */
-    lcd_puts_P(STUD_NAME);
-    lcd_goto(0x40); /* Got to the beginning of the next line */
+static inline void start_ui (void)
+{
+    // Print program and libc versions
+    fprintf_P(stderr, PSTR(PROG_VERSION "\n"),
+              PSTR(GIT_DESCR), PSTR(__DATE__), PSTR(__TIME__));
+    fprintf_P(stderr, PSTR(LIBC_VERSION "\n"), PSTR(__AVR_LIBC_VERSION_STRING__));
 
-    /* ASCII table print */
+    // print student name
+    fprintf_P(stdout, PSTR(STUD_NAME));
+    fputc('\n', stdout); // Add a new line to the uart printout
+    lcd_puts_P(PSTR(STUD_NAME));
+
+    // ASCII table print
     print_ascii_tbl(stdout);
-    unsigned char ascii[128] = {0};
+    unsigned char ascii[128];
     for (unsigned char i = 0; i < sizeof(ascii); i++) {
         ascii[i] = i;
     }
     print_for_human(stdout, ascii, sizeof(ascii));
 
-    while (1) {
-        /* set pin 3 high to turn led on */
-        PORTA |= _BV(PORTA3);
-        _delay_ms(BLINK_DELAY_MS);
+    // Bootstrap search_month message
+    fprintf_P(stdout, PSTR(GET_MONTH_MSG));
+}
 
-        /* Month search and print */
-        char month_first_leter;
-        fprintf_P(stdout, GET_MONTH_MSG);
-        fscanf(stdin, "%c", &month_first_leter);
-        fprintf(stdout, "%c\n", month_first_leter);
-        for (int i = 0; i < 6; i++) {
-            if (!strncmp_P(&month_first_leter, ENG_MONTH[i], 1)) {
-                fprintf_P(stdout, ENG_MONTH[i]);
-                fputc('\n', stdout);
-                lcd_puts_P(ENG_MONTH[i]);
-                lcd_putc(' ');
-            }
+static inline void search_month (void)
+{
+    char letter;
+
+    fscanf(stdin, "%c", &letter);
+    fprintf(stdout, "%c\n", letter);
+    lcd_goto(0x40); // Got to the beginning of the next line
+    for (int i = 0; i < 6; i++) {
+        if (!strncmp_P(&letter, (PGM_P)pgm_read_word(&months[i]), 1)) {
+            fprintf_P(stdout, (PGM_P)pgm_read_word(&months[i]));
+            fputc('\n', stdout);
+            lcd_puts_P((PGM_P)pgm_read_word(&months[i]));
+            lcd_putc(' ');
         }
-        lcd_puts_P(PSTR("                ")); /* Clear the end of the line */
-        lcd_goto(0x40); /* Got to the beginning of the next line */
+    }
 
+    // this is fine because even when the hd44780 address counter goes over 0xf4
+    // we still have quite a few addresses left until address counter overflow
+    // and we also dont care about the data that is at the end of the ddram
+    lcd_puts_P(PSTR("                ")); // Clear the end of the line
+    fprintf_P(stdout, PSTR(GET_MONTH_MSG));
+}
 
-        /* set pin 3 low to turn led off */
-        PORTA &= ~_BV(PORTA3);
-        _delay_ms(BLINK_DELAY_MS);
+static inline void heartbeat (void)
+{
+    static time_t time_prev;
+    time_t time_cur = time(NULL);
+    if (time_cur <= time_prev) {
+        return;
+    }
+    time_prev = time_cur;
+    fprintf_P(stderr, PSTR(UPTIME_MSG "\n"), time_cur);
+    LED_TOGGLE;
+}
+
+int main (void)
+{
+    init_hw();
+    start_ui();
+
+    while (1) {
+        heartbeat();
+        if (uart0_available()) {
+            search_month();
+        }
     }
 }
+
+// System clock
+ISR(TIMER5_COMPA_vect)
+{
+    system_tick();
+}

src/print_helper.c

@@ -1,27 +1,33 @@
 #include <stdio.h>
+#include <avr/pgmspace.h>
 #include "print_helper.h"
 
-int print_ascii_tbl (FILE *stream) {
+int print_ascii_tbl (FILE *stream)
+{
     for (char c = ' '; c <= '~'; c++) {
-        if(!fprintf(stream, "%c ", c)) {
+        if (!fprintf(stream, "%c ", c)) {
             return 0;
         }
     }
+
     return fprintf(stream, "\n");
 }
 
 
-int print_for_human (FILE *stream, const unsigned char *array, const int len) {
+int print_for_human (FILE *stream, const unsigned char *array, const int len)
+{
     for (int i = 0; i < len; i++) {
-        if (array[i] >= ' ' && array[i] <= '~') {
-            if(!fprintf(stream, "%c", array[i])) {
+        unsigned char c = array[i];
+        if (c >= ' ' && c <= '~') {
+            if (!fprintf(stream, "%c", c)) {
                 return 0;
             }
         } else {
-            if(!fprintf(stream, "\"0x%02x\"", array[i])) {
+            if (!fprintf(stream, "\"0x%02x\"", c)) {
                 return 0;
             }
         }
     }
-    return fprintf(stream, "\n");;
+
+    return fprintf(stream, "\n");
 }

src/uart.c

@@ -1,72 +0,0 @@
-#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

@@ -1,17 +0,0 @@
-#ifndef _UART_H_
-#define _UART_H_
-
-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);
-
-#endif /* _UART_H_ */

src/uart_wrap.c

@@ -0,0 +1,37 @@
+#include <avr/io.h>
+#include <stdio.h>
+#include "../lib/andygock_avr-uart/uart.h"
+
+int uart0_putc_wrap(char c, FILE *stream)
+{
+    (void) stream;
+
+    if (c == '\n') {
+        uart0_putc_wrap('\r', stream);
+    }
+
+    uart0_putc(c);
+    return 0;
+}
+
+int uart0_getc_wrap(FILE *stream)
+{
+    (void) stream;
+    // Probabbly should add some error checking in here but because
+    // this function is only called out when there is at least one character
+    // available in the input buffer (see main.c line 114) then error checking
+    // is not currently necessary.
+    return (char)uart0_getc();
+}
+
+int uart3_putc_wrap(char c, FILE *stream)
+{
+    (void) stream;
+
+    if (c == '\n') {
+        uart3_putc_wrap('\r', stream);
+    }
+
+    uart3_putc(c);
+    return 0;
+}

src/uart_wrap.h

@@ -0,0 +1,15 @@
+#ifndef _UART_WRAP_H_
+#define _UART_WRAP_H_
+
+int uart0_putc_wrap(char c, FILE *stream);
+int uart0_getc_wrap(FILE *stream);
+
+int uart3_putc_wrap(char c, FILE *stream);
+
+
+/* http://www.ermicro.com/blog/?p=325 */
+
+FILE uart0_io = FDEV_SETUP_STREAM(uart0_putc_wrap, uart0_getc_wrap, _FDEV_SETUP_RW);
+FILE uart3_out = FDEV_SETUP_STREAM(uart3_putc_wrap, NULL, _FDEV_SETUP_WRITE);
+
+#endif /* _UART_WRAP_H_ */

tooling/format-code.sh

@@ -18,10 +18,8 @@ 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 \