Looking at your screenshot you are doing well. This is exactly as I'd expect as you are sending from chip and it is being received by the Terminal program.
All is good


Next I'd suggest you modify the SendString command to instead of sending "U" it sends "U\r\n"
You should now get
U
U
U
etc
Once you are comfortable sending from chip to PC we will modify your chart so the chip can receive data you send from the PC to the chip. There are a few ways to do this and I'll give brief examples of a couple. It is better to understand these concepts now before progressing to the module.
Regards
PS
My view is that any post is valuable. Just because something doesn't work as hoped doesn't mean it is worthless. Others may have similar issues to you and may think on giving up, but perhaps after reading of your experiences they will continue. The issues you faced updating the firmware, which did stump me for a bit, did get resolved and I know the posts have been helpful to others. Had you not faced these issues I'd never have explored the issue further and perhaps it wouldn't be documented for others.