Colony

/**

 * Copyright (c) 2007 Colony Project

 * 

 * Permission is hereby granted, free of charge, to any person

 * obtaining a copy of this software and associated documentation

 * files (the "Software"), to deal in the Software without

 * restriction, including without limitation the rights to use,

 * copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following

 * conditions:

 * 

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 * 

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES

 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT

 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,

 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

 * OTHER DEALINGS IN THE SOFTWARE.

 **/

/** @file i2c.h

 *  @brief Header file for I2C

 *

 *  Contains functions for I2C.

 *

 *  @author Kevin Woo and Suresh Nidhiry, Colony Project, CMU Robotics Club

 **/

#ifndef _I2C_H_

#define _I2C_H_

#include <stddef.h>

/** @brief Address of slave receive handler function **/

typedef void (*fun_srecv_t)(char);

/** @brief Address of master receive handler function**/

typedef int (*fun_mrecv_t)(char);

/** @brief Address of slave send handler function**/

typedef char (*fun_send_t)(void);

int i2c_init(char addr, fun_mrecv_t master_recv, fun_srecv_t slave_recv, fun_send_t slave_send);

int i2c_send(char dest, char* data, size_t bytes);

int i2c_request(char dest);

void i2c_packet_rec (char i2c_byte);

void i2c_packet_sniff(char data);

#endif

#include <dragonfly_lib.h>

int main(void) {

	dragonfly_init(ALL_ON);

	return 0;

}

# Hey Emacs, this is a -*- makefile -*-

#----------------------------------------------------------------------------

# WinAVR Makefile Template written by Eric B. Weddington, J?rg Wunsch, et al.

#

# Released to the Public Domain

#

# Additional material for this makefile was written by:

# Peter Fleury

# Tim Henigan

# Colin O'Flynn

# Reiner Patommel

# Markus Pfaff

# Sander Pool

# Frederik Rouleau

#

#----------------------------------------------------------------------------

# On command line:

#

# make all = Make software.

#

# make clean = Clean out built project files.

#

# make coff = Convert ELF to AVR COFF.

#

# make extcoff = Convert ELF to AVR Extended COFF.

#

# make program = Download the hex file to the device, using avrdude.

#                Please customize the avrdude settings below first!

#

# make debug = Start either simulavr or avarice as specified for debugging, 

#              with avr-gdb or avr-insight as the front end for debugging.

#

# make filename.s = Just compile filename.c into the assembler code only.

#

# make filename.i = Create a preprocessed source file for use in submitting

#                   bug reports to the GCC project.

#

# To rebuild project do "make clean" then "make all".

#----------------------------------------------------------------------------

# MCU name

MCU = atmega164p

# Processor frequency.

#     This will define a symbol, F_CPU, in all source code files equal to the 

#     processor frequency. You can then use this symbol in your source code to 

#     calculate timings. Do NOT tack on a 'UL' at the end, this will be done

#     automatically to create a 32-bit value in your source code.

F_CPU = 5000000

# Output format. (can be srec, ihex, binary)

FORMAT = ihex

# Target file name (without extension).

TARGET = timerBlink

# List C source files here. (C dependencies are automatically generated.)

SRC = $(TARGET).c

# List Assembler source files here.

#     Make them always end in a capital .S.  Files ending in a lowercase .s

#     will not be considered source files but generated files (assembler

#     output from the compiler), and will be deleted upon "make clean"!

#     Even though the DOS/Win* filesystem matches both .s and .S the same,

#     it will preserve the spelling of the filenames, and gcc itself does

#     care about how the name is spelled on its command-line.

ASRC = 

# Optimization level, can be [0, 1, 2, 3, s]. 

#     0 = turn off optimization. s = optimize for size.

#     (Note: 3 is not always the best optimization level. See avr-libc FAQ.)

OPT = s

# Debugging format.

#     Native formats for AVR-GCC's -g are dwarf-2 [default] or stabs.

#     AVR Studio 4.10 requires dwarf-2.

#     AVR [Extended] COFF format requires stabs, plus an avr-objcopy run.

DEBUG = dwarf-2

# List any extra directories to look for include files here.

#     Each directory must be seperated by a space.

#     Use forward slashes for directory separators.

#     For a directory that has spaces, enclose it in quotes.

#EXTRAINCDIRS = C:\WinAVR\include\fwr

# Compiler flag to set the C Standard level.

#     c89   = "ANSI" C

#     gnu89 = c89 plus GCC extensions

#     c99   = ISO C99 standard (not yet fully implemented)

#     gnu99 = c99 plus GCC extensions

CSTANDARD = -std=gnu99

# Place -D or -U options here

CDEFS = -DF_CPU=$(F_CPU)UL

# Place -I options here

CINCS =

#---------------- Compiler Options ----------------

#  -g*:          generate debugging information

#  -O*:          optimization level

#  -f...:        tuning, see GCC manual and avr-libc documentation

#  -Wall...:     warning level

#  -Wa,...:      tell GCC to pass this to the assembler.

#    -adhlns...: create assembler listing

CFLAGS = -g$(DEBUG)

CFLAGS += $(CDEFS) $(CINCS)

CFLAGS += -O$(OPT)

CFLAGS += -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums

CFLAGS += -Wall -Wstrict-prototypes

CFLAGS += -Wa,-adhlns=$(<:.c=.lst)

CFLAGS += $(patsubst %,-I%,$(EXTRAINCDIRS))

CFLAGS += $(CSTANDARD)

#---------------- Assembler Options ----------------

#  -Wa,...:   tell GCC to pass this to the assembler.

#  -ahlms:    create listing

#  -gstabs:   have the assembler create line number information; note that

#             for use in COFF files, additional information about filenames

#             and function names needs to be present in the assembler source

#             files -- see avr-libc docs [FIXME: not yet described there]

ASFLAGS = -Wa,-adhlns=$(<:.S=.lst),-gstabs 

#---------------- Library Options ----------------

# Minimalistic printf version

PRINTF_LIB_MIN = -Wl,-u,vfprintf -lprintf_min

# Floating point printf version (requires MATH_LIB = -lm below)

PRINTF_LIB_FLOAT = -Wl,-u,vfprintf -lprintf_flt

# If this is left blank, then it will use the Standard printf version.

PRINTF_LIB = 

#PRINTF_LIB = $(PRINTF_LIB_MIN)

#PRINTF_LIB = $(PRINTF_LIB_FLOAT)

# Minimalistic scanf version

SCANF_LIB_MIN = -Wl,-u,vfscanf -lscanf_min

# Floating point + %[ scanf version (requires MATH_LIB = -lm below)

SCANF_LIB_FLOAT = -Wl,-u,vfscanf -lscanf_flt

# If this is left blank, then it will use the Standard scanf version.

SCANF_LIB = 

#SCANF_LIB = $(SCANF_LIB_MIN)

#SCANF_LIB = $(SCANF_LIB_FLOAT)

MATH_LIB = -lm

#---------------- External Memory Options ----------------

# 64 KB of external RAM, starting after internal RAM (ATmega128!),

# used for variables (.data/.bss) and heap (malloc()).

#EXTMEMOPTS = -Wl,-Tdata=0x801100,--defsym=__heap_end=0x80ffff

# 64 KB of external RAM, starting after internal RAM (ATmega128!),

# only used for heap (malloc()).

#EXTMEMOPTS = -Wl,--defsym=__heap_start=0x801100,--defsym=__heap_end=0x80ffff

EXTMEMOPTS =

#---------------- Linker Options ----------------

#  -Wl,...:     tell GCC to pass this to linker.

#    -Map:      create map file

#    --cref:    add cross reference to  map file

LDFLAGS = -Wl,-Map=$(TARGET).map,--cref

LDFLAGS += $(EXTMEMOPTS)

LDFLAGS += $(PRINTF_LIB) $(SCANF_LIB) $(MATH_LIB)

#---------------- Programming Options (avrdude) ----------------

# Programming hardware: alf avr910 avrisp bascom bsd 

# dt006 pavr picoweb pony-stk200 sp12 stk200 stk500

#

# Type: avrdude -c ?

# to get a full listing.

#

AVRDUDE_PROGRAMMER = avrisp

# com1 = serial port. Use lpt1 to connect to parallel port.

AVRDUDE_PORT = com1

# programmer connected to serial device

AVRDUDE_WRITE_FLASH = -b 4800 -U flash:w:$(TARGET).hex

#AVRDUDE_WRITE_EEPROM = -U eeprom:w:$(TARGET).eep

# Uncomment the following if you want avrdude's erase cycle counter.

# Note that this counter needs to be initialized first using -Yn,

# see avrdude manual.

#AVRDUDE_ERASE_COUNTER = -y

# Uncomment the following if you do /not/ wish a verification to be

# performed after programming the device.

#AVRDUDE_NO_VERIFY = -V

# Increase verbosity level.  Please use this when submitting bug

# reports about avrdude. See <http://savannah.nongnu.org/projects/avrdude> 

# to submit bug reports.

#AVRDUDE_VERBOSE = -v -v

AVRDUDE_FLAGS = -p $(MCU) -P $(AVRDUDE_PORT) -c $(AVRDUDE_PROGRAMMER)

AVRDUDE_FLAGS += $(AVRDUDE_NO_VERIFY)

AVRDUDE_FLAGS += $(AVRDUDE_VERBOSE)

AVRDUDE_FLAGS += $(AVRDUDE_ERASE_COUNTER)

#---------------- Debugging Options ----------------

# For simulavr only - target MCU frequency.

DEBUG_MFREQ = $(F_CPU)

# Set the DEBUG_UI to either gdb or insight.

# DEBUG_UI = gdb

DEBUG_UI = insight

# Set the debugging back-end to either avarice, simulavr.

DEBUG_BACKEND = avarice

#DEBUG_BACKEND = simulavr

# GDB Init Filename.

GDBINIT_FILE = __avr_gdbinit

# When using avarice settings for the JTAG

JTAG_DEV = /dev/com1

# Debugging port used to communicate between GDB / avarice / simulavr.

DEBUG_PORT = 4242

# Debugging host used to communicate between GDB / avarice / simulavr, normally

#     just set to localhost unless doing some sort of crazy debugging when 

#     avarice is running on a different computer.

DEBUG_HOST = localhost

#============================================================================

# Define programs and commands.

SHELL = sh

CC = avr-gcc

OBJCOPY = avr-objcopy

OBJDUMP = avr-objdump

SIZE = avr-size

NM = avr-nm

AVRDUDE = avrdude

REMOVE = rm -f

COPY = cp

WINSHELL = cmd

# Define Messages

# English

MSG_ERRORS_NONE = Errors: none

MSG_BEGIN = -------- begin --------

MSG_END = --------  end  --------

MSG_SIZE_BEFORE = Size before: 

MSG_SIZE_AFTER = Size after:

MSG_COFF = Converting to AVR COFF:

MSG_EXTENDED_COFF = Converting to AVR Extended COFF:

MSG_FLASH = Creating load file for Flash:

MSG_EEPROM = Creating load file for EEPROM:

MSG_EXTENDED_LISTING = Creating Extended Listing:

MSG_SYMBOL_TABLE = Creating Symbol Table:

MSG_LINKING = Linking:

MSG_COMPILING = Compiling:

MSG_ASSEMBLING = Assembling:

MSG_CLEANING = Cleaning project:

# Define all object files.

OBJ = $(SRC:.c=.o) $(ASRC:.S=.o) 

# Define all listing files.

LST = $(SRC:.c=.lst) $(ASRC:.S=.lst) 

# Compiler flags to generate dependency files.

GENDEPFLAGS = -MD -MP -MF .dep/$(@F).d

# Combine all necessary flags and optional flags.

# Add target processor to flags.

ALL_CFLAGS = -mmcu=$(MCU) -I. $(CFLAGS) $(GENDEPFLAGS)

ALL_ASFLAGS = -mmcu=$(MCU) -I. -x assembler-with-cpp $(ASFLAGS)

# Default target.

all: begin gccversion sizebefore build sizeafter end

build: elf hex eep lss sym

elf: $(TARGET).elf

hex: $(TARGET).hex

eep: $(TARGET).eep

lss: $(TARGET).lss 

sym: $(TARGET).sym

# Eye candy.

# AVR Studio 3.x does not check make's exit code but relies on

# the following magic strings to be generated by the compile job.

begin:

	@echo

	@echo $(MSG_BEGIN)

end:

	@echo $(MSG_END)

	@echo

# Display size of file.

HEXSIZE = $(SIZE) --target=$(FORMAT) $(TARGET).hex

ELFSIZE = $(SIZE) -A $(TARGET).elf

AVRMEM = avr-mem.sh $(TARGET).elf $(MCU)

sizebefore:

	@if test -f $(TARGET).elf; then echo; echo $(MSG_SIZE_BEFORE); $(ELFSIZE); \

	$(AVRMEM) 2>/dev/null; echo; fi

sizeafter:

	@if test -f $(TARGET).elf; then echo; echo $(MSG_SIZE_AFTER); $(ELFSIZE); \

	$(AVRMEM) 2>/dev/null; echo; fi

# Display compiler version information.

gccversion : 

	@$(CC) --version

# Program the device.  

program: $(TARGET).hex $(TARGET).eep

	$(AVRDUDE) $(AVRDUDE_FLAGS) $(AVRDUDE_WRITE_FLASH) $(AVRDUDE_WRITE_EEPROM)

# Generate avr-gdb config/init file which does the following:

#     define the reset signal, load the target file, connect to target, and set 

#     a breakpoint at main().

gdb-config: 

	@$(REMOVE) $(GDBINIT_FILE)

	@echo define reset >> $(GDBINIT_FILE)

	@echo SIGNAL SIGHUP >> $(GDBINIT_FILE)

	@echo end >> $(GDBINIT_FILE)

	@echo file $(TARGET).elf >> $(GDBINIT_FILE)

	@echo target remote $(DEBUG_HOST):$(DEBUG_PORT)  >> $(GDBINIT_FILE)

ifeq ($(DEBUG_BACKEND),simulavr)

	@echo load  >> $(GDBINIT_FILE)

endif	

	@echo break main >> $(GDBINIT_FILE)

debug: gdb-config $(TARGET).elf

ifeq ($(DEBUG_BACKEND), avarice)

	@echo Starting AVaRICE - Press enter when "waiting to connect" message displays.

	@$(WINSHELL) /c start avarice --jtag $(JTAG_DEV) --erase --program --file \

	$(TARGET).elf $(DEBUG_HOST):$(DEBUG_PORT)

	@$(WINSHELL) /c pause

else

	@$(WINSHELL) /c start simulavr --gdbserver --device $(MCU) --clock-freq \

	$(DEBUG_MFREQ) --port $(DEBUG_PORT)

endif

	@$(WINSHELL) /c start avr-$(DEBUG_UI) --command=$(GDBINIT_FILE)

# Convert ELF to COFF for use in debugging / simulating in AVR Studio or VMLAB.

COFFCONVERT=$(OBJCOPY) --debugging \

--change-section-address .data-0x800000 \

--change-section-address .bss-0x800000 \

--change-section-address .noinit-0x800000 \

--change-section-address .eeprom-0x810000 

coff: $(TARGET).elf

	@echo

	@echo $(MSG_COFF) $(TARGET).cof

	$(COFFCONVERT) -O coff-avr $< $(TARGET).cof

extcoff: $(TARGET).elf

	@echo

	@echo $(MSG_EXTENDED_COFF) $(TARGET).cof

	$(COFFCONVERT) -O coff-ext-avr $< $(TARGET).cof

# Create final output files (.hex, .eep) from ELF output file.

%.hex: %.elf

	@echo

	@echo $(MSG_FLASH) $@

	$(OBJCOPY) -O $(FORMAT) -R .eeprom $< $@

%.eep: %.elf

	@echo

	@echo $(MSG_EEPROM) $@

	-$(OBJCOPY) -j .eeprom --set-section-flags=.eeprom="alloc,load" \

	--change-section-lma .eeprom=0 -O $(FORMAT) $< $@

# Create extended listing file from ELF output file.

%.lss: %.elf

	@echo

	@echo $(MSG_EXTENDED_LISTING) $@

	$(OBJDUMP) -h -S $< > $@

# Create a symbol table from ELF output file.

%.sym: %.elf

	@echo

	@echo $(MSG_SYMBOL_TABLE) $@

	$(NM) -n $< > $@

# Link: create ELF output file from object files.

.SECONDARY : $(TARGET).elf

.PRECIOUS : $(OBJ)

%.elf: $(OBJ)

	@echo

	@echo $(MSG_LINKING) $@

	$(CC) $(ALL_CFLAGS) $^ --output $@ $(LDFLAGS)

# Compile: create object files from C source files.

%.o : %.c

	@echo

	@echo $(MSG_COMPILING) $<

	$(CC) -c $(ALL_CFLAGS) $< -o $@ 

# Compile: create assembler files from C source files.

%.s : %.c

	$(CC) -S $(ALL_CFLAGS) $< -o $@

# Assemble: create object files from assembler source files.

%.o : %.S

	@echo

	@echo $(MSG_ASSEMBLING) $<

	$(CC) -c $(ALL_ASFLAGS) $< -o $@

# Create preprocessed source for use in sending a bug report.

%.i : %.c

	$(CC) -E -mmcu=$(MCU) -I. $(CFLAGS) $< -o $@ 

# Target: clean project.

clean: begin clean_list end

clean_list :

	@echo

	@echo $(MSG_CLEANING)

	$(REMOVE) $(TARGET).hex

	$(REMOVE) $(TARGET).eep

	$(REMOVE) $(TARGET).cof

	$(REMOVE) $(TARGET).elf

	$(REMOVE) $(TARGET).map

	$(REMOVE) $(TARGET).sym

	$(REMOVE) $(TARGET).lss

	$(REMOVE) $(OBJ)

	$(REMOVE) $(LST)

	$(REMOVE) $(SRC:.c=.s)

	$(REMOVE) $(SRC:.c=.d)

	$(REMOVE) .dep/*

# Include the dependency files.

-include $(shell mkdir .dep 2>/dev/null) $(wildcard .dep/*)

# Listing of phony targets.

.PHONY : all begin finish end sizebefore sizeafter gccversion \

build elf hex eep lss sym coff extcoff \

clean clean_list program debug gdb-config

/**

 * Copyright (c) 2007 Colony Project

 * 

 * Permission is hereby granted, free of charge, to any person

 * obtaining a copy of this software and associated documentation

 * files (the "Software"), to deal in the Software without

 * restriction, including without limitation the rights to use,

 * copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following

 * conditions:

 * 

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 * 

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES

 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT

 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,

 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR

 * OTHER DEALINGS IN THE SOFTWARE.

 **/

/**

 * @file i2c.c

 * @brief Implemenation of I2C communications protocol

 * 

 * In the case where you have master sends and then a master request to the same

 * address, you will not give up control of the line because the send and

 * request addresses are seen as different addresses. In between it will send a

 * restart but will not give up the line.

 *

 * @author CMU Robotics Club, Kevin Woo, Sursh Nidhiry

 * @bug Not tested.

 */

#include <avr/interrupt.h>

#include <util/twi.h>

#include "i2c.h"

#include "ring_buffer.h"

/**

 * @defgroup i2c I2C 

 *

 * @brief Provides Inter-Interconnected-Communications (I2C)

 * 

 * Initiates I2C functions on an ATMega128 which has a fully hardware Two Wire 

 * Interface (TWI) module. Any Atmel chip with this hardware should be able to

 * use the software.

 *

 * This code will operate in a multi-master enviornment and can be either a

 * slave or a master at any time (as long as they are not one or the other at

 * the moment. You can queue up multiple transmission modes in the buffer up to 

 * the buffer size. The buffer is implemented as a ring buffer.

 *

 * It is implemented using callback functions. Whenever you want to send a packet

 * you can call the built in send function (as a master) and it will send an array

 * of bytes. Master recieve and slave send/receive are all handled by the call back

 * functions. It is up to the end user to create functions that will handle the

 * receiving of packets. Their functions will be called with every byte recieved

 * so you must either buffer the inputs or handle each one separately.

 *

 * On errors we will simply flush the entire buffer.

 * 

 * For information on how I2C operates, read the wikipedia article

 * http://en.wikipedia.org/wiki/I2c

 * for a good explanation of how it works.

 * @{

 */

/** 

 * @brief Set bit rate 12 = 100kbit/s (max speed setting is 10 for an

 *  8 MHz clock). It is a divider, so the lower the number the faster the speed.

 */

#define I2C_BIT_RATE_DIVIDER 0x0C

static int start_flag;

static fun_mrecv_t master_recv_function;

static fun_srecv_t slave_recv_function;

static fun_send_t slave_send_function;

RING_BUFFER_NEW(i2c_buffer, 128, char, i2c_write_buff, i2c_addr_buff);

/**

 * @brief Initializes the i2c module.

 *

 * Initializes the I2C module to start listening on the i2c lines. If the callback functions

 * are not set to null they will be called when that transmission mode is called. The address

 * is your address that you will listen to when you are not the master.

 *

 * @param addr 			Your address on the I2C bus.

 * @param master_recv 	The address of the function to call when you receive a byte when you are a

 *                    	master.

 * @param slave_recv 	The address of the function to call when you are a slave you receive data

 *								from the master

 * @param slave_send		The address of the function to call when you are a slave and the master

 *								requests data from you.

 *

 * @return 0 for success, nonzero for failure

 **/

int i2c_init(char addr, fun_mrecv_t master_recv, fun_srecv_t slave_recv, fun_send_t slave_send) {

    master_recv_function = master_recv;

    slave_recv_function = slave_recv;

    slave_send_function = slave_send;

    RING_BUFFER_CLEAR(i2c_write_buff);

    RING_BUFFER_CLEAR(i2c_addr_buff);

    /* enables twi interrupt, automatic ack sending, and all twi hardware */

    TWCR =  (_BV(TWEA) | _BV(TWEN) | _BV(TWIE));

    /* sets the bit rate of data transmission */

    TWBR = I2C_BIT_RATE_DIVIDER;

    /* sets the address (it is stored in the 7 most significant bits) and allows

     * global messages to be accepted */

    TWAR = (addr << 1) | 1;

    return 0;

}

/**

 * @brief Sends a byte array over I2C as a master

 *

 * Will perform a send over I2C to the destination from data for the ammount of

 * bytes that bytes is.

 *

 * @param dest		Destination address of the data on the I2C bus.

 * @param data 	The pointer to the byte array of data

 * @param bytes	The amount of bytes long that the byte array is. This is how

 *						many bytes from the array that the function will send.

 *

 * @return zero for success, nonzero for failure

 **/

int i2c_send(char dest, char *data, size_t bytes) {

    int i;

    /* adding data to be sent to ring buffers is not atomic,

     * so disable interrupts */

    cli();

    for(i = 0; i < bytes; i++) {

        if(RING_BUFFER_FULL(i2c_write_buff)) {

            sei();

            return -1;

        }

        RING_BUFFER_ADD(i2c_write_buff, data[i]);

        RING_BUFFER_ADD(i2c_addr_buff, dest << 1);

    }

    /* re-enable the interrupts */

    sei();

    /* send the start bit, only if this device is not currently master */

    if(!start_flag) {

        start_flag = 1;

        TWCR |= _BV(TWSTA);

        TWCR |= _BV(TWINT);

    }

    return 0;

}

/**

 * @brief Send a master request to the destination

 *

 * Sends a request of data from the target address and calls

 * the callback function to handle data as it comes in. This function will

 * not work if the slave has not informationt to send or has nothing implemented

 * to send it.

 *

 * @param dest		The destination that we want to receive information from.

 *

 * @return 0 for success, nonzero for failure

 **/ 

int i2c_request(char dest) {

    if(RING_BUFFER_FULL(i2c_write_buff))

        return -1;

    RING_BUFFER_ADD(i2c_write_buff, 0);

    RING_BUFFER_ADD(i2c_addr_buff, (dest << 1) | 1);

    if(!start_flag) {

        start_flag = 1;

        TWCR |= _BV(TWSTA);

        TWCR |= _BV(TWINT);

    }

    return 0;

}

/** @} **/

/**

 * @brief Interrupt to handle I2C interrupts from the I2C hardware.

 * 

 * Uses the status codes from the I2C register to handle the events

 * needed to advance in I2C stages. For instance, you will get a bit for

 * receiving a start ack, then a address ack, then a data ack, etc.

 * The events are handled in each switch case. The status codes are defined

 * by avr-gcc in /util/twi.h but are the same codes as the Atmel documentation.

 *

 * Bytes are sent by popping off the ring buffer. It also will keep track

 * of what modes the send is in.

 *

 * Errors are handled here as well.

 **/ 

ISR(TWI_vect) {

	static char data_to_send;

	static char addr_to_send = -1;

	char addr, statusCode;

	//Get status code (only upper 5 bits)

	statusCode = (TWSR & 0xF8);

    switch (statusCode) {

        //Start sent successfully

        case TW_START:

        case TW_REP_START:

            /* Send address and write

             * ring_buffer will not be empty */

            RING_BUFFER_REMOVE(i2c_addr_buff, addr_to_send);

            RING_BUFFER_REMOVE(i2c_write_buff, data_to_send);

            /* first send the address */

            TWDR = addr_to_send; 

            //Turn off start bits

            TWCR &= ~_BV(TWSTA);

            break;

        //Master Transmit - Address sent succesfully

        case TW_MT_SLA_ACK:

        //Send byte

            TWDR = data_to_send;

            PORTG &= ~_BV(PG2);

            break;

        //Master Transmit - Data sent succesfully

        case TW_MT_DATA_ACK:    

            //If there is still data to send

            if(!RING_BUFFER_EMPTY(i2c_write_buff)) {

                RING_BUFFER_PEEK(i2c_addr_buff, addr);

                //Still data for this address

                if (addr == addr_to_send) {

                    RING_BUFFER_REMOVE(i2c_addr_buff, addr);

                    RING_BUFFER_REMOVE(i2c_write_buff, TWDR);

                    break;

                //No more data for this address, data for another address -> resend start

                } else {

                    TWCR |= _BV(TWSTA);

                    break;

                }

            }

            /* there are no bytes to send */

            TWCR |= _BV(TWSTO);

            start_flag = 0;

            break; 

        //Master Transmit - Slave sends a nack, transmit is done

        case TW_MT_DATA_NACK:

            PORTG |= _BV(PG2);

            TWCR |= _BV(TWSTO);

            start_flag = 0;

            break;

        //Master Receive - Address sent succesfully

        case TW_MR_SLA_ACK:

            PORTG |= _BV(PG2);

            break;

        //Master Receive - Data received succesfully

        case TW_MR_DATA_ACK:

            if(master_recv_function) {

                if(!master_recv_function(TWDR)) {

                    TWCR &= ~_BV(TWEA);

                }

            }

            break;

        //Master Receive - Slave sends a nack, transmission is done    

        case TW_MR_DATA_NACK:

            TWCR |= _BV(TWEA);

            //If there is still data to send

            if(!RING_BUFFER_EMPTY(i2c_write_buff)) {

                TWCR |= _BV(TWSTA);

                break;

            }

            /* there are no bytes to send */

            TWCR |= _BV(TWSTO);

            start_flag = 0;  

            break;

        //Slave Transmit - Address received

        case TW_ST_SLA_ACK:

            break;

        //Slave Transmit - Nack received, no data requsted

        case TW_ST_DATA_NACK:

            break;

        //Slave Transmit - Data requested, ack received

        case TW_ST_DATA_ACK:

            if (slave_send_function) {

                TWDR = slave_send_function();

            }

            break;

        //Slave Receive - Address received  

        case TW_SR_SLA_ACK:

            break;

        //Slave Receive - Data received, ack returned

        case TW_SR_DATA_ACK:

            if(slave_recv_function) {

                slave_recv_function(TWDR);

            }

            break;

        //Stop sent  

        case TW_SR_STOP:

            break;

        //Problem on the bus, reset everything

        default:

            TWCR |= _BV(TWSTO);

            start_flag = 0;

            RING_BUFFER_CLEAR(i2c_write_buff);

            RING_BUFFER_CLEAR(i2c_addr_buff);  	

    }

  /* Toggle TWINT so that it resets and executes the commands */

  TWCR |= _BV(TWINT);

}