I have the V2.81 hdwe and recently downloaded the bootloader code (1st 16K) with the STM serial interface. The download only provides a hex file and the upload to flash anything requires a BIN file.
So the question is whether I can use a HEX to BIN convertor to enable me to upload this bootloader code???
Merle
OK, after some research I found SW that will let me review the HEX file and also save it in BIN. Interesting notes I found in the code… The micro controller being used is the STM32F103VE. There was some other data regarding the FPGA I believe.
I can put both of the files up if anyone is interested. I can’t validate them since my Quad is not working in the DFU mode. At least it is the bootloader for V2.81. If someone has a Brick then they can try uploading it.
Merle
I’d be interested to see the dumps.
They are not of direct use to me as I have earlier hardware and a 3.11C DFU. However, I did do a simple disassem of that version to see the Licensing handling so I may be able to do some sort of rough comparison.
I have attached a zip file of the HEX and BIN files for the V2.81 bootloader on my Quad.
Hopefully it works, I have not used the “create” portion of ZIP in a rather long time.
BOOTDSOV340C16K (2).zip (11 KB)
Let me explain what I did first. I experimented last time with various FPGA/SYS/APP and I can’t remember what versions I mixed up, but after all I gave up.
When I tried your file today, it worked! It complained only about that licence code. Then I wanted to update FPGA/SYS/APP with latest versions for my HW2.81, but unfortunately it is now complaining about FPGA error on startup. So it works with some of the older FPGA/SYS/APP combinations, which I can’t remember 
so I still need to wait for SEEED stuff for their official release of DFU for HW2.81
Thank you wagnermerle anyway! Really appreciate.
Can you, please, provide some info or link to that hex2bin software you have used?