AVR Bootloader (avrboot cleanup)
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Olaf Rempel 1509afc016 Version 0.85 (20081203) 10 years ago
ldscripts_no_vector Version 0.80beta3 (20060528) 12 years ago
testapp Version 0.83 (20080412) 10 years ago
testavrdude Version 0.83 (20080412) 10 years ago
avrprog_boot.pnproj Version 0.83 (20080412) 10 years ago
avrprog_boot.pnps Version 0.80beta3 (20060528) 12 years ago
chipdef.h Version 0.84 (20081106) 10 years ago
main Version 0.83 (20080412) 10 years ago
main.c Version 0.85 (20081203) 10 years ago
makefile Version 0.84 (20081106) 10 years ago
mega8.h Version 0.85 (20081203) 10 years ago
mega16.h Version 0.85 (20081203) 10 years ago
mega32.h Version 0.85 (20081203) 10 years ago
mega64.h Version 0.85 (20081203) 10 years ago
mega128.h Version 0.85 (20081203) 10 years ago
mega128can.h Version 0.85 (20081203) 10 years ago
mega162.h Version 0.85 (20081203) 10 years ago
mega169.h Version 0.85 (20081203) 10 years ago
mega324p.h Version 0.83 (20080412) 10 years ago
mega644.h Version 0.85 (20081203) 10 years ago
mega644p.h Version 0.83 (20080412) 10 years ago
megaxx4p.h Version 0.85 (20081203) 10 years ago
readme.txt Version 0.85 (20081203) 10 years ago



ATMEL AVR UART Bootloader for AVR-GCC/avr-libc

by Martin Thomas, Kaiserslautern, Germany

** Addtional code and improvements contributed **
** by Uwe Bonnes, Bjoern Riemer and Olaf Rempel. **

Eearly versions of this bootloader-code have been
based on the AVR Butterfly bootloader-source REV02
which has been available from atmel.com.


Programming-Software (on the "PC-Side"):

* AVRProg (included in AVRStudio) available at www.atmel.com.
MS-Windows only. AVRProg can be used as stand-alone application.

* avrdude available at http://savannah.nongnu.org/projects/avrdude/

* Installation instructions at the end of this file.

3. Dec. 2008 - Version 0.85

* disable U2X before jump to app as suggested be Alexander Döller
* moved UBRR-macros to main.c and changed them. Inspired by code from avr-libc setbaud.
(macros which are commented out (//) are from Pavel Fertser)

6. Nov. 2008 - Version 0.84

* Added definitions for ATmega64 provided by Pavel Fertser - Thanks.

12. Apr. 2008 - Version 0.83

* Added definitions for ATmega644P and ATmega324P
* Tested with ATmega324P, gcc 4.2.2, avr-libc 1.4.6
* Added testapp to verify "exit bootloader" with
watchdog (n.b.: watchdog-disable called early in testapp)

27. Jan. 2007 - Version 0.82

* Added definitions for ATmega644.
* Using avr-lib's eeprom-functions (old "direct-access"-code
has not been compatible with ATmega644).
* Watchdog-disable at startup (configurable): avoids problems with
repeated login to bootloader. Not needed if the bootloader is
never re-entered again between an "exit programming" and
a system-reset/power-toogle.
* Additional watchdog disable-function for ATmega644.
* Made watchdog-enable time at exit-programming a configuration-value
* Bootloader read-protection: if enabled the bootloader fakes
an empty boot-section (configurable by define)
Since more of the avr-libc functions's are used this version
should be more portable for other AVRs but the size of the
binary increases a little bit.
Make sure to disable the watchdog early in the user-application
esp. when using a "modern" AVR (i.e. ATmega48/88/168/644/324P/644P).

3. Dec. 2006 - Version 0.81

* Added definitions for ATmega162.
* Fixed init for double-speed (bitmask). Thanks to Bernhard Roth

28. May 2006 - Version 0.8beta3

* Supports discarding of interrupt-vectors which saves some space
if no interrupts are needed in the bootloader. Added option
in makefile to enable this feature, modified LDFLAGS,
additional code in main.c for a pseudo default_interrupt ISR.
The modified linker-scripts have been contributed by
Olaf Rempel (basicly just the .vector-section is not linked).
* Reverted the order of signatur-byte-numbers in part-
configurations to the usual order in the datasheet,
also reverted in main.c for sending the signature.
* Definitions for lock/fuse-readout.
* Updated installation-instruction at the end of this file.
* Added DEVTYPE_ISP/DEVTYPE_BOOT to part-configurations,
added configuration-option for this in main.c.
* A remark about the DEVTYPE: Usualy there are two
Part-Codes/Device-Codes. One is for ISP: AVRProg shows
the type of the AVR. The other code is for bootloading:
AVRprog shows the type plus "BOOT". When a boot-device-code
gets detected by AVRprog it "knows" how do handle the
limited functionality of bootloaders. (When receiving the
ISP-code AVRProg expects an AVR910-type programmer.)
The offset between the codes is usualy 0x01 where the
ISP-code is the smaller value, i.e. ATmega32 ISP-code
is 0x72->"ATmega32" and boot-code is 0x73->"ATmega32 BOOT".
When using avrdude the bootloader's device-code must match
the device-code in the avrdude.conf. Check the avrdude-
code to see if both codes (AVR910 and AVR109) are supported.
-- I have got some e-mails from users which have been
confused by this. Hopefully this explanation is good enough.
* This bootloader lets the watchdog do a reset when the
user selects "Exit programmer" (i.e. in AVRProg) after an
update. Make sure to disable or reset the watchdog early in
your application.

27. May 2006 - Version 0.8beta2

* More very well done improvements contributed by Olaf Rempel.
* Olaf Rempel also modified the STARTUP_WAIT method.

21. May 2006 - Version 0.8beta

* Version contributed by Olaf Rempel. He has done a lot of modifications.
-> "cleaner code", smaller binaries.

09. Feb. 2006 - Version 0.75

* additional STARTUP_WAIT support contributed by Bjoern Riemer

18. Aug. 2005 - Version 0.74

* AT90CAN128 support contributed by Uwe Bonnes
* Makefile modifications contributed by Uwe Bonnes

23. Feb. 2005 - Version 0.7

* (Version 0.6 has never been available on the web-page)
* ATmega128 support
* code cleanup
* This version has been tested with ATmega8, ATmega32 and

7. Apr. 2004 - Version 0.5

* added different startup-methods
* compatible with ATmega8 now
* included makefile adapted to ATmega8 now
(ATmega16 options still available)
* fixed jump to application which did not work
reliably before
* tested with ATmega8
* minimal options and startup-code result in
bootloader-size < 512 words

6. Apr. 2004 - Version 0.4

* Buffered read of chars from UART during programming
since eeprom-write is too slow for unbuffered
operation. So EEPROM-upload does work now.
* Added BOOTICE-mode to flash JTAGICE-compatible
hardware (ATmega16@7,3Mhz) (if you know about BOOTICE,
you may unterstand why this has been added, if not
just keep the option disabled)
* small changes in (my)boot.h (lock-bit-mask) found
out during the development of the STK-500-compatible
bootloader. But setting lock-bits still does not
work with this bootloader.
* read of the low-fuse byte works (high byte still TODO)
* read of the lock-byte works (write still TODO)

27. Mar 2004 - Version 0.3

Felt that as much functions from avr-libc's boot.h
as possible should be used without modifications.
Latest CVS-version of boot.h is included.
Only the read-routine is still "self-made" based
on ATMELs assembler-code.
EEPROM write on Mega16 does not work (and did not
work with V0.2 too). May be caused by my old Mega16
chip. Needs testing. Flash read/write and EEPROM
read works. Still only tested with ATmega16.
This version may not work with the ATmega169 any

24. Mar 2004 - Version 0.2

During the development of a data-logger application
with the AVR-Butterfly there was a need to make
some changes in the bootloader. The same problem
again: no IAR compiler. The same way to solve the
problem: a port of the code to avr-gcc/avr-libc.
So this code is based on the ATMEL Butterfly
bootloader source code Rev 0.2 for IAR.

The bootloader-port for the Butterfly which mimics
the complete functionality of the original
BF-bootloader is availabe at:

Atmel used a separate "lib" written in "pure"
assembly to access the low-level functions
for flash read/write. Well, so far I
don't know how to use "mixed language sources"
with the avr-gcc toolchain, so the low-level
routines have been implemented as inline assembler.
The avr-libc boot.h module written by Eric
Weddington served as a template Three of the four
low-level routines found in lowlevel.c come from
boot.h with minimal changes. The read routine has
been developed based on the ATMEL assembler code.

Ignore the fuse and lock-bit readout. Read and Set is
not enabled (TODO).

--------------- Installation -----------------

- Change the MCU type in the makefile.

- Change the boot(loader)-size in Makefile. The needed
space depends on the features selected in main.c

- Set baudrate in main.c, a doublespeed configuration-option
is available too.

- Change the F_CPU in main.c to the clock-frequency
of your board. See the datasheet for frequencies
with minimum error at the selected baudrate.

- Select the start-condition in main.c.

- Please use at least avr-gcc 3.3.1/avr-libc 1.0
or WINAVR Sept. 2003 or later to compile and link
this bootloader.

- Upload the hex-File to the AVR (STK500, STK200, SP12
evertool, AVR910 etc.)

- Program the "Boot Flash section size" (BOOTSZ fuses)
according to the boot-size selected in the makefile
i.e. BOOTSZ=00 for boot-size 1024 words (2048 bytes)
on ATmega16

- enable the BOOT Reset Vector fuse (BOOTRST=0)

- Set the lock bits to protect the bootloader from
SPM-writes (Boot Loader Protection Mode 2 in STK500-
plugin) so that it can not overwrite itself.

- Connect the AVR UART Pins via level-shifter/inverter
(i.e. MAX232) to your PCs COM-Port.

- Reset the AVR while fullfilling the bootloader start-
condition. (Default: selected pin connected to GND).
The condition must be "true" until you see the
AVRPROG dialog or avrdude connects.

- Start AVRPROG (AVRStudio/Tools or stand-alone avrprog.exe)
AVRDUDE is supported too, check it's manual
for command-line options. Read the text above for
information about Device-Types and AVRDUDE

- AVRPROG or AVRDUDE should detect the bootloader.

- see AVRStudio's online-help for more information how
to use AVRPROG

- make sure to EXIT from AVRPROG (button) to start
your main-application or toogle power/reset.

Feedback welcome, Good luck.