AM261-SOM-EVM: AM261x: Secure Boot is not working

Hello everyone,

I am currently working on the AM261x-LP platform and aiming to implement secure boot on my product. For reference, I have been using the hello_world example project.

Here is what I have done so far:

1. I have read the AM261x MCU+SDK developer guide on enabling secure boot:
   https://software-dl.ti.com/mcu-plus-sdk/esd/AM261X/latest/exports/docs/api_guide_am261x/SECURE_BOOT.html

2. I built the SBL image using the following make command:
   make -s -C examples/drivers/boot/sbl_ospi/am261x-lp/r5fss0-0_nortos/ti-arm-clang all DEVICE=am261x DEVICE_TYPE=HS
   
   This produced the file: sbl_ospi.release.hs.tiimage 

3. Similarly, I built the application image using the command:
   make -s -C examples/hello_world/am261x-lp/r5fss0-0_freertos/ti-arm-clang all DEVICE=am261x DEVICE_TYPE=HS
   
   This produced the file: hello_world.release.appimage.hs 
4. I successfully flashed ospi_sbl and hello_world.release.appimage. Both the OSPI bootloader and the application boot and print output on the serial console correctly.
   
   
   
5. However, when I flash sbl_ospi.release.hs.tiimage and hello_world.release.appimage.hs, I do not see any output on the serial console.
   
   I have read about enabling secure boot and understand that when building the SBL and application using the make commands, the generated binaries (with the extension .hs) are already signed. From what I gather, these images use a TI-dummy key for signing by default. Is that correct? 
   
   Could anyone please help me understand what might be causing this issue?