How to modify existing bootloader.

[ADINV]

Hi, I need to modify the bootloader of the STM32F427 MCU.

Specifically, I need to modify the UART portion of the bootloader so that it works with RS485.

This should just involve adding a control line for direction flow.

So, my questions:

1. Is the source code available for the default bootloader so that I can add this simple modification?
2. Are there instructions for how to program the modified bootloader?

Thanks

[Tesla DeLorean]

Source code is not user modifiable (ROM/OTP), and not provided.

If you currently sell 1M units, discuss your specific needs with sales.

Write your own loader that fits in one of the first 16KB sector(s), and have your distributor program this prior to delivery to your board house.

Or use JTAG/SWD via edge castellations or test points, or usual headers.