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

  by Martin Thomas, Kaiserslautern, Germany

  mthomas@rhrk.uni-kl.de

  eversmith@heizung-thomas.de

  http://www.siwawi.arubi.uni-kl.de/avr_projects

  **  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.

  (avrprog.exe)

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

  "Multiplattform"

* 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 

  (define).

* 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 

  ATmega128

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

more.

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:

www.siwawi.arubi.uni-kl.de/avr_projects

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.

Martin