activate dead code removal, update README

Makefile

@@ -6,23 +6,22 @@
 MCU_TARGET  = atmega1284p # Target device to be used (32K or lager)
 BOOT_ADR    = 0x1F000	# Boot loader start address [byte] NOT [word] as in http://eleccelerator.com/fusecalc/fusecalc.php?chip=atmega1284p
 F_CPU       = 16000000	# CPU clock frequency [Hz]
-USE_LED     = 0		# Define two leds in asmfunc.S (mainly for debug!!!) 
-USE_UART    = 16	# Debug on Serial. 0 ... deactivate or divider of http://wormfood.net/avrbaudcalc.php for baud rate!
-			# !!!Enable uart/uart.c or uncomment to save 382 bytes !!!
+USE_LED     = 0		# Debug with two (defined in asmfunc.S)
+USE_UART    = 1		# Debug on Serial. 0 ... deactivate or divider of http://wormfood.net/avrbaudcalc.php for baud rate!
 #------------------------------------------------------------------
-CSRC        = main.c pff/src/pff.c diskio.c uart/uart.c #Please help to make this conditional on USE_UART
+CSRC        = main.c pff/src/pff.c diskio.c uart/uart.c #uart/uart.c is taken out by --gc,sections is USE_UART = 0
 
 TARGET      = avr_boot
 ASRC        = asmfunc.S
-OPTIMIZE    = -Os -mcall-prologues
+OPTIMIZE    = -Os -mcall-prologues -ffunction-sections -fdata-sections
 DEFS        = -DBOOT_ADR=$(BOOT_ADR) -DF_CPU=$(F_CPU) -DUSE_LED=$(USE_LED) -DUSE_UART=$(USE_UART)
 LIBS        =
 DEBUG       = dwarf-2
 
 ASFLAGS     = -Wa,-adhlns=$(<:.S=.lst),-gstabs $(DEFS)
 ALL_ASFLAGS = -mmcu=$(MCU_TARGET) -I. -x assembler-with-cpp $(ASFLAGS)
 CFLAGS      = -g$(DEBUG) -Wall $(OPTIMIZE) -mmcu=$(MCU_TARGET) -std=c99 $(DEFS)
-LDFLAGS     = -Wl,-Map,$(TARGET).map -Wl,--section-start,.text=$(BOOT_ADR)
+LDFLAGS     = -Wl,-Map,$(TARGET).map -Wl,--gc-sections -Wl,--section-start,.text=$(BOOT_ADR)
 OBJ         = $(CSRC:.c=.o) $(ASRC:.S=.o)
 
 CC          = avr-gcc
@@ -31,7 +30,7 @@ OBJDUMP     = avr-objdump
 SIZE        = avr-size
 
 
-all:	$(TARGET).elf lst text bin size
+all:	clean $(TARGET).elf lst text bin size
 
 $(TARGET).elf: $(OBJ)
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ $(LIBS)

README.md

@@ -5,37 +5,47 @@ SD card Bootloader for atmega processors
 
 As easy as it can get! I spent days with this. Hopefully you wont!
 
-- for any ATMega with SD Card
-- Petit FatFs R0.03 for FAT16 && FAT32
-- 4096kB Bootloader required
-- CRC Check or EEprom can be easily added - look into main.c
-
-...*BUT* I prefere to keep things simple. Instead of an elaborate versioning systems avr_boot checks on one filename and will reflash as long as it finds this filename. This is not a problem since, it happens nearly instantly and only differing bytes are flashed.
-You may put the logic as well into the application (which you want to distribute) and delete or rename the firmware file.
-
+- for any ATMega with 4096kb Bootloader
+- uses Petit FatFs R0.03 for FAT16 && FAT32
+- looks for FIRMWARE.BIN and flashes it nearly instantly
+- without any interference to your application
+- simple check before starting your application or retry every 5 seconds
+- no CRC Check and no version bytes in EEPROM (see More...)
 
 # Usage
 
 This is with avr-gcc and avrdude under linux with an Atmega1284p! Adaption to your case (WinAvr) will not be too complicated...
 
 - adapt Makefile
   - MCU_TARGET: Your AtmegaXXX (maybe not relevant?)
-  - BOOT_ADR: in bytes not words.
+  - BOOT_ADR: in bytes not words!
   - F_CPU:  CPU Frequency
   - USE_LED: For debugging 0...deactivate or 1...active
-  - USE_UART: For debugging 0...deactivate  or divider for baudate see http://wormfood.net/avrbaudcalc.php
+  - USE_UART: For debugging 0...deactivate or divider for baudate see http://wormfood.net/avrbaudcalc.php
 - adapt pins in asmfunc.S
 - adapt pff/src/pffconfh.h
 - adapt filename of firmware (now FIRMWARE.BIN) in main.c 
-- make clean
 - make
 - set fuses: avrdude -c avrispmkII -p m1284p -U hfuse:w:0xda:m
-  - find high fuse in http://eleccelerator.com/fusecalc/fusecalc.php?chip=atmega1284p 
+  - find high fuse in http://eleccelerator.com/fusecalc/fusecalc.php?chip=atmega1284p
 - flash: avrdude -c avrispmkII -p m1284p -Uflash:w:./avr_boot.hex:i -Ulock:w:0x3F:m 
 - get your app.cpp.hex (out of /tmp/buildxxx in case of Arduino IDE)
 - make bin file: avr-objcopy -I ihex -O binary app.cpp.hex FIRMWARE.BIN
 - copy the file into the root of an SD (FAT12/FAT16/FAT32)
-- it might already have happen!. Flashing is nearly instantly (unless USE_LED=1)
+- put it into the SD slot of your Atmega
+- reset it
+- it might already have happend!
+
+# Bootloader size
+ - 3540 bytes
+ - 3852 bytes debugging with USE_LED
+ - 3934 bytes debugging with USE_UART
+ - 4240 bytes debugging with USE_LED and USE_UART (does not fit in 4096)
+
+# More ...
+ ... if you wish you *can* add CRC Check or versioning with EEPROM *but* I prefere to keep things simple. avr_boot will reflash your FIRMWARE.BIN as long as it is present.
+Is this a problem? No! It happens nearly instantly and only differing bytes are flashed really.
+You may consider putting your logic into your application and perform a CRC Check after the fact to inform the user and deleting or renaming FIRMWARE.BIN
 
 # Thanks to
 - http://elm-chan.org/fsw/ff/00index_p.html