Similar to Will the Uno bootloader work in the Duemilanove? but the other way around.
I have an Arduino Uno. I require a slower upload speed than the 115200 baud rate used in the Uno's Optiboot bootloader.
The Arduino Duemilanove uses the ATmegaBOOT_168_atmega328 bootloader which has an upload baud rate of 57600. The Arduino Duemilanove also uses the ATMega328P like used on the Arduino Uno.
Will the Duemilanove bootloader work in the Uno?
Yes it will.
Both the Arduino Duemilanove and Arduino Uno use the ATMega328P microcontroller. (There is also a version of Arduino Duemilanove ATMega168 that uses the Diecimila bootloader and that is not compatible, so just watch out).
The main difference between the Arduino Duemilanove and the Arduino Uno is that the Duemilanove uses FTDI FT232R IC, whereas the Uno uses the Atmega8u2 microcontroller fto handle the USB to serial UART interface.
Also important is that both boards both have the same 16MHz clock rate.
The schematic for the Arduino Duemilanove can be found here.
The schematic for the Arduino Uno can be found here.
Of course, instead of selecting Arduino Uno as the board type, you need to always select Arduino Duemilanove or Diecimila and the ATmega328 processor.
The question asks about Y problem. Here is the solution for the problem X in this X->Y situation.
I require a slower upload speed than the 115200 baud rate used in the Uno's Optiboot bootloader.
The Optiboot bootloader can work on different UART baud rates. The baud rate is configurable as parameter of the make command at build.
If don't want to setup the toolchain for compilation of the bootloader, MCUdude has on GitHub ready Optiboot hex files compiled with many options.
I recommend to use a custom boards definition for boards with not standard settings to burn the bootloader and to upload to the board. Here I have my https://github.com/jandrassy/my_boards as example.
