Investigate Booster serial port usage with TeraTerm and Putty

[ryan-summers]

We have had a number of reports that users struggle to get Booster's serial port to function when communicating with Putty or TeraTerm. Users report that no output is shown and can't communicate with the device, but other descriptions of device functionality seem to indicate that Booster is otherwise operating normally (e.g. fan startup self test is heard, LEDs show disabled channels).

[ryan-summers]

It appears that this is the result of Putty not sending a \n when the user presses Enter. Instead, Putty sends just <CR>. In putty, the only way to insert a is using Ctrl+J.

Interestingly, even enabling "Implicit LF on CR" does not appear to resolve the issue. The user is required to press Ctrl+J to submit a command with the current design.

[jordens]

Speculating: maybe the latter is because then cmd<CR><LF> is not recognized the way cmd<LF> would be.

[ryan-summers]

Currently, firmware just looks for the b'\n' character, which is a single LF. If there's a prepended , that should still cause it to parse the command and would still work.

With the local echo, it can be seen in the Putty display that no newline is created (so no is sent by Putty and echo'd back). I think we should just accept either or as the termination character.