I have an Uno with atmeg328 chip. I need to slow down the upload baud rate on my uno when I upload a sketch. I have changed the upload speed in board.txt and recompiled the optiboot bootloader file
but the uno will only upload a sketch at speed 115200. I tried also changing the baud rates in the
optiboot.c file and recompiled but no matter what I do the only baudrate that will work is 115200.
How can I change this to perhaps 2400? Is there any way of doing this with the uno or is the
USBtinyIsp limited to just 115200? Thanks
Can you show the verbose log of compiling optiboot, and burning it onto your Uno? It sounds like your "burn bootloader" command may be picking up the old version of the optiboot .hex file.
Also, consider using the newest optiboot from Google Code Archive - Long-term storage for Google Code Project Hosting.
It is easier to compile with different options, and it had some fixes to non-standard bitrates.
Thanks for your reply, Sorry for the delay in this response! Below is the log and as
you can see it states a baud of 115200, I don't know where this number is coming from
because I have no such number in the optiboot.c file which I changed to 2400. I Also don't
know if this 115200 is affecting the upload function of the UNO.
Also
I have changed the upload baud in Boards.txt to 2400 (the upload rate is what I am trying to
slow down). My chip will get the bootload and I believe it is indeed trying to upload
at 2400 but the UNO itself can't sync with the chip and errors out when I attempt to upload.
When I read the product description of the UNO it describes it as a 115200 device
leading me to believe I can't change the upload rate of an UNO. If true why is there a selection
to do so in the boards.txt file?
I have deleted optiboot hex files and tried bootloading and received errors which are corrected
when I replace the hex file so I am pretty sure that the bootloader is grabbing the correct files
that I have been editing.
Thanks for your help!
C:\Program Files\Arduino\hardware\arduino\bootloaders\optiboot>......\tools\av
r\utils\bin\make OS=windows ENV=arduino atmega328
../../../tools/avr/bin/avr-gcc -g -Wall -Os -fno-inline-small-functions -fno-spl
it-wide-types -mshort-calls -mmcu=atmega328p -DF_CPU=16000000L '-DLED_START_FLA
SHES=3' '-DBAUD_RATE=115200' -c -o optiboot.o optiboot.c
../../../tools/avr/bin/avr-gcc -g -Wall -Os -fno-inline-small-functions -fno-spl
it-wide-types -mshort-calls -mmcu=atmega328p -DF_CPU=16000000L '-DLED_START_FLA
SHES=3' '-DBAUD_RATE=115200' -W1,--section-start=.text=0x7e00 -W1,--section-star
t=.version=0x7ffe -W1,--relax -W1,--gc-sections -nostartfiles -nostdlib -o optib
oot_atmega328.elf optiboot.o
../../../tools/avr/bin/avr-size optiboot_atmega328.elf
text data bss dec hex filename
500 0 0 500 1f4 optiboot_atmega328.elf
../../../tools/avr/bin/avr-objcopy -j .text -j .data -j .version --set-section-f
lags .version=alloc,load -O ihex optiboot_atmega328.elf optiboot_atmega328.hex
......\tools\avr\bin\avr-objdump -h -S optiboot_atmega328.elf > optiboot_atmeg
a328.lst
rm optiboot.o optiboot_atmega328.elf
I have changed the upload speed in board.txt and recompiled the optiboot bootloader file
Ah hah! The upload speed in boards.txt has nothing to do with the compilation of optiboot.
To change optiboot, you need to change the compilation by editing the makefile.
Or if you get the newer source, you can do:
omake atmega328 BAUD_RATE=19200
? I will try this, but I only want to change the baudrate with which the Uno uploads a sketch to the chip I don't
care what the Baudrate is when it loads the bootloader. It doesn't make sense to me. I had tried changing
the rate by editing the optiboot.c file and doing an omake to create the hex files. Thanks