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bf 537 stamp, uart boot problem

Hello, I am new to working with the ADZS-BF537-STAMP board. I tried to transfer the bootloader to the board in order to install Linux in the future. The first thing I did: Moved the boot mode switch to position 7, switch SW4 to the OFF ON OFF OFF position, switch SW6 to the ON ON ON ON position and removed the jumper JP9.

Then, according to the instructions, I checked whether there is a connection with the board, restarted the board 9 times, constantly pressing the space bar, received 9 answers, one answer per reboot, so USB->Serial Converter (RS232) is working fine and there is a connection, I used minicom on Ubuntu OS 20.04 to check.

Next, I put the jumper JP9 and received in the minicom window what I enter on the keyboard, then removed the jumper again.
After that, I downloaded GNU Toolchain for linux from sourceforge.
Next, the most interesting thing is, using bfin-uclinux-ldr, I tried to load u-boot onto the board, but I ran into this

Even if the baud rate is not set manually, the result is the same.
Repeated attempts to restart the board and start transferring u-boot to the board again did not lead to success.
ldrviewer also does not work, responds the time has expired.
I hope someone can help me with solving this problem, thank you in advance!